[GitHub] [carbondata] ajantha-bhat opened a new pull request #3770: [CARBONDATA-3829] Support pagination in SDK reader

[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433644354



##########
File path: python/pycarbon/sdk/PaginationCarbonReader.py
##########
@@ -0,0 +1,57 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class PaginationCarbonReader(object):
+  def __init__(self):
+    from jnius import autoclass
+    self.readerClass = autoclass('org.apache.carbondata.sdk.file.PaginationCarbonReader')
+
+  def builder(self, path, table_name):
+    self.PaginationCarbonReaderBuilder = self.readerClass.builder(path, table_name)
+    return self
+
+  def projection(self, projection_list):
+    self.PaginationCarbonReaderBuilder.projection(projection_list)
+    return self
+
+  def withHadoopConf(self, key, value):

Review comment:
       That temporary AK SK is a separate requirement. Once PR raised for that, can python code in the same PR.




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[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433650373



##########
File path: python/pycarbon/tests/sdk/test_read_write_carbon.py
##########
@@ -25,7 +26,8 @@
 import os
 import jnius_config
 
-jnius_config.set_classpath("../../../sdk/sdk/target/carbondata-sdk.jar")
+jnius_config.set_classpath("../../../../sdk/sdk/target/carbondata-sdk.jar")
+# jnius_config.add_options('-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=6666')

Review comment:
       done




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[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433650411



##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,276 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {
+      throw new IllegalArgumentException(
+          "to row id:" + to + " is greater than total rows:" + getTotalRows());
+    }
+    return getRows(from, to);
+  }
+
+  /**
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public long getTotalRows() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return rowCountInSplits.get(rowCountInSplits.size() - 1);
+  }
+
+  /**
+   * This interface is for python to call java.
+   * Because python cannot understand java Long object. so send string object.
+   *
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public String getTotalRowsAsString() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return (rowCountInSplits.get(rowCountInSplits.size() - 1)).toString();
+  }
+
+  private static int findBlockletIndex(List<Long> summationArray2, Long key) {
+    // summation array is in sorted order, so can use the binary search.
+    int index = Collections.binarySearch(summationArray2, key);
+    if (index < 0) {
+      // when key not found, binary search returns negative index [-1 to -N].
+      // which is the possible place where key can be inserted.
+      // with one shifted position. As 0 is also a valid index.
+      index = index + 1; // offset the one index shifted.
+      index = Math.abs(index);
+    }
+    return index;
+  }
+
+  private int[] getBlockletIndexRange(long from, long to) {
+    // find the matching blocklet index range by checking with from and to.
+    int upperBound = findBlockletIndex(rowCountInSplits, to);
+    // lower bound cannot be more than upper bound, so work on sub list.
+    int lowerBound = findBlockletIndex(rowCountInSplits.subList(0, upperBound), from);
+    return new int[] {lowerBound, upperBound};
+  }
+
+  private Object[] getRows(long from, long to)
+      throws IOException, InterruptedException {
+    int rowCount = 0;
+    Object[] rows = new Object[(int)(to - from + 1)];
+    // get the matching split index (blocklets) range for the input range.
+    int[] blockletIndexRange = getBlockletIndexRange(from, to);
+    for (int i = blockletIndexRange[0]; i <= blockletIndexRange[1]; i++) {

Review comment:
       done

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,276 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {
+      throw new IllegalArgumentException(
+          "to row id:" + to + " is greater than total rows:" + getTotalRows());
+    }
+    return getRows(from, to);
+  }
+
+  /**
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public long getTotalRows() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return rowCountInSplits.get(rowCountInSplits.size() - 1);
+  }
+
+  /**
+   * This interface is for python to call java.
+   * Because python cannot understand java Long object. so send string object.
+   *
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public String getTotalRowsAsString() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return (rowCountInSplits.get(rowCountInSplits.size() - 1)).toString();
+  }
+
+  private static int findBlockletIndex(List<Long> summationArray2, Long key) {
+    // summation array is in sorted order, so can use the binary search.
+    int index = Collections.binarySearch(summationArray2, key);
+    if (index < 0) {
+      // when key not found, binary search returns negative index [-1 to -N].
+      // which is the possible place where key can be inserted.
+      // with one shifted position. As 0 is also a valid index.
+      index = index + 1; // offset the one index shifted.
+      index = Math.abs(index);
+    }
+    return index;
+  }
+
+  private int[] getBlockletIndexRange(long from, long to) {
+    // find the matching blocklet index range by checking with from and to.
+    int upperBound = findBlockletIndex(rowCountInSplits, to);
+    // lower bound cannot be more than upper bound, so work on sub list.
+    int lowerBound = findBlockletIndex(rowCountInSplits.subList(0, upperBound), from);
+    return new int[] {lowerBound, upperBound};

Review comment:
       done

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,276 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {
+      throw new IllegalArgumentException(
+          "to row id:" + to + " is greater than total rows:" + getTotalRows());
+    }
+    return getRows(from, to);
+  }
+
+  /**
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public long getTotalRows() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return rowCountInSplits.get(rowCountInSplits.size() - 1);
+  }
+
+  /**
+   * This interface is for python to call java.
+   * Because python cannot understand java Long object. so send string object.
+   *
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public String getTotalRowsAsString() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return (rowCountInSplits.get(rowCountInSplits.size() - 1)).toString();
+  }
+
+  private static int findBlockletIndex(List<Long> summationArray2, Long key) {
+    // summation array is in sorted order, so can use the binary search.
+    int index = Collections.binarySearch(summationArray2, key);
+    if (index < 0) {
+      // when key not found, binary search returns negative index [-1 to -N].
+      // which is the possible place where key can be inserted.
+      // with one shifted position. As 0 is also a valid index.
+      index = index + 1; // offset the one index shifted.
+      index = Math.abs(index);

Review comment:
       done

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,276 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {
+      throw new IllegalArgumentException(
+          "to row id:" + to + " is greater than total rows:" + getTotalRows());
+    }
+    return getRows(from, to);
+  }
+
+  /**
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public long getTotalRows() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return rowCountInSplits.get(rowCountInSplits.size() - 1);
+  }
+
+  /**
+   * This interface is for python to call java.
+   * Because python cannot understand java Long object. so send string object.
+   *
+   * Get total rows in the folder.
+   * It is based on the snapshot of files taken while building the reader.
+   *
+   *
+   * @return total rows from all the files in the reader.
+   */
+  public String getTotalRowsAsString() {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    return (rowCountInSplits.get(rowCountInSplits.size() - 1)).toString();
+  }
+
+  private static int findBlockletIndex(List<Long> summationArray2, Long key) {

Review comment:
       fixed

##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,39 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param from must be greater than 0 and <= to
+* @param to must be >= from and not outside the total rows
+* @return array of rows between from and to (inclusive)
+* @throws Exception
+*/
+public Object[] read(long from, long to) throws IOException, InterruptedException;
+```
+
+```
+/**
+* Get total rows in the folder.

Review comment:
       done




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CarbonDataQA1 commented on pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#issuecomment-637399742


   Build Success with Spark 2.4.5, Please check CI http://121.244.95.60:12545/job/ApacheCarbon_PR_Builder_2.4.5/1398/
   


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CarbonDataQA1 commented on pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#issuecomment-637401136


   Build Success with Spark 2.3.4, Please check CI http://121.244.95.60:12545/job/ApacheCarbonPRBuilder2.3/3122/
   


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xubo245 commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433798210



##########
File path: python/pycarbon/sdk/PaginationCarbonReader.py
##########
@@ -0,0 +1,57 @@
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class PaginationCarbonReader(object):
+  def __init__(self):
+    from jnius import autoclass
+    self.readerClass = autoclass('org.apache.carbondata.sdk.file.PaginationCarbonReader')
+
+  def builder(self, path, table_name):
+    self.PaginationCarbonReaderBuilder = self.readerClass.builder(path, table_name)
+    return self
+
+  def projection(self, projection_list):
+    self.PaginationCarbonReaderBuilder.projection(projection_list)
+    return self
+
+  def withHadoopConf(self, key, value):

Review comment:
       ok




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xubo245 commented on pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#issuecomment-637469617


   LGTM


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jackylk commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433800964



##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to

Review comment:
       should mention what is the value stands for, is it the row number?
   if yes, change the parameter name to `fromRowNumber`




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jackylk commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433801885



##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {

Review comment:
       Is parameter starts from 0 or 1? should mention in line 85




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[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433807579



##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {

Review comment:
       In line 86, I have mentioned 'to' must be >= 'from'
   so, this has to be greater than 0.
   
   If still need to mention. I can add.




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ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433808273



##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to

Review comment:
       ok, I will change. both from and to




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ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r433877801



##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to

Review comment:
       done. renamed all occurrence and document.

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,296 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param from must be greater than 0 and <= to
+   * @param to must be >= from and not outside the total rows
+   * @return array of rows between from and to (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long from, long to) throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (from < 1) {
+      throw new IllegalArgumentException("from row id:" + from + " is less than 1");
+    }
+    if (from > to) {
+      throw new IllegalArgumentException(
+          "from row id:" + from + " is greater than to row id:" + to);
+    }
+    if (to > getTotalRows()) {

Review comment:
       added




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CarbonDataQA1 commented on pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#issuecomment-637638738


   Build Success with Spark 2.3.4, Please check CI http://121.244.95.60:12545/job/ApacheCarbonPRBuilder2.3/3123/
   


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CarbonDataQA1 commented on pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#issuecomment-637641946


   Build Success with Spark 2.4.5, Please check CI http://121.244.95.60:12545/job/ApacheCarbon_PR_Builder_2.4.5/1399/
   


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akashrn5 commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r434325061



##########
File path: docs/configuration-parameters.md
##########
@@ -141,6 +141,7 @@ This section provides the details of all the configurations required for the Car
 | carbon.load.all.segment.indexes.to.cache | true | Setting this configuration to false, will prune and load only matched segment indexes to cache using segment metadata information such as columnid and it's minmax values, which decreases the usage of driver memory.  |
 | carbon.secondary.index.creation.threads | 1 | Specifies the number of threads to concurrently process segments during secondary index creation. This property helps fine tuning the system when there are a lot of segments in a table. The value range is 1 to 50. |
 | carbon.si.lookup.partialstring | true | When true, it includes starts with, ends with and contains. When false, it includes only starts with secondary indexes. |
+| carbon.max.pagination.lru.cache.size.in.mb | -1 | Maximum memory **(in MB)** upto which the SDK pagination reader can cache the blocklet rows. Suggest to configure as multiple of blocklet size. Default value of -1 means there is no memory limit for caching. Only integer values greater than 0 are accepted. |

Review comment:
       `configure as multiple of blocklet size` for this in the bracket can you mention an example?

##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,41 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param fromRowNumber must be greater 0 (as row id starts from 1)
+*                      and less than equal to toRowNumber

Review comment:
       `less than or equal to`

##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,41 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param fromRowNumber must be greater 0 (as row id starts from 1)
+*                      and less than equal to toRowNumber
+* @param toRowNumber must be greater than 0 (as row id starts from 1)
+*                and greater than equals to fromRowNumber and not outside the total rows

Review comment:
       change `greater than equals to fromRowNumber and not outside the total rows`  to `greater than or equal to fromRowNumber and should not cross the total rows count value`

##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,41 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param fromRowNumber must be greater 0 (as row id starts from 1)
+*                      and less than equal to toRowNumber
+* @param toRowNumber must be greater than 0 (as row id starts from 1)
+*                and greater than equals to fromRowNumber and not outside the total rows
+* @return array of rows between fromRowNumber and toRowNumber (inclusive)
+* @throws Exception
+*/
+public Object[] read(long fromRowNumber, long toRowNumber) throws IOException, InterruptedException;
+```
+
+```
+/**
+* Get total rows in the folder or a list of CarbonData files.
+* It is based on the snapshot of files taken while building the reader.
+*
+* @return total rows from all the files in the reader.
+*/
+public long getTotalRows();
+```
+
+```
+/**
+* Closes the pagination reader, drops the cache and snapshot.
+* Need to build reader again if the files need to be read again.
+* Suggest to call this when new files are added in the folder.

Review comment:
       ```suggestion
   * Do not call this unless new files are added in the folder of you want to drop the cache.
   ```

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,302 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param fromRowNumber must be greater 0 (as row id starts from 1)
+   *                      and less than equal to toRowNumber
+   * @param toRowNumber must be greater than 0 (as row id starts from 1)

Review comment:
       please change the method java doc similar with comments above for md files

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,302 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param fromRowNumber must be greater 0 (as row id starts from 1)
+   *                      and less than equal to toRowNumber
+   * @param toRowNumber must be greater than 0 (as row id starts from 1)
+   *                and greater than equals to fromRowNumber and not outside the total rows
+   * @return array of rows between fromRowNumber and toRowNumber (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long fromRowNumber, long toRowNumber)
+      throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (fromRowNumber < 1) {
+      throw new IllegalArgumentException("from row id:" + fromRowNumber + " is less than 1");
+    }
+    if (fromRowNumber > toRowNumber) {
+      throw new IllegalArgumentException(

Review comment:
       same as above for all error messages, please change to a meaningful message like the above suggestion

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,302 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param fromRowNumber must be greater 0 (as row id starts from 1)
+   *                      and less than equal to toRowNumber
+   * @param toRowNumber must be greater than 0 (as row id starts from 1)
+   *                and greater than equals to fromRowNumber and not outside the total rows
+   * @return array of rows between fromRowNumber and toRowNumber (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long fromRowNumber, long toRowNumber)
+      throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (fromRowNumber < 1) {
+      throw new IllegalArgumentException("from row id:" + fromRowNumber + " is less than 1");

Review comment:
       ```suggestion
         throw new IllegalArgumentException("Starting row number :" + fromRowNumber + " of pagination read is less than 1");
   ```

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,302 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();

Review comment:
       rename `sum` to `summationOfRowsInEachBlocklet`, this would be meaningful




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[GitBox]

akashrn5 commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r434379315



##########
File path: sdk/sdk/src/test/java/org/apache/carbondata/sdk/file/PaginationCarbonReaderTest.java
##########
@@ -0,0 +1,221 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.metadata.datatype.DataTypes;
+import org.apache.carbondata.core.metadata.datatype.Field;
+import org.apache.carbondata.core.util.CarbonProperties;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.lang.RandomStringUtils;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Test suite for {@link CSVCarbonWriter}
+ */
+public class PaginationCarbonReaderTest {

Review comment:
       can you add test cases for negative scenarios also, which throws exceptions?

##########
File path: sdk/sdk/src/main/java/org/apache/carbondata/sdk/file/PaginationCarbonReader.java
##########
@@ -0,0 +1,302 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.carbondata.sdk.file;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.carbondata.common.annotations.InterfaceAudience;
+import org.apache.carbondata.common.annotations.InterfaceStability;
+import org.apache.carbondata.core.cache.CarbonLRUCache;
+import org.apache.carbondata.core.constants.CarbonCommonConstants;
+import org.apache.carbondata.core.indexstore.BlockletDetailInfo;
+import org.apache.carbondata.hadoop.CarbonInputSplit;
+import org.apache.carbondata.sdk.file.cache.BlockletRows;
+
+import org.apache.hadoop.mapreduce.InputSplit;
+
+/**
+ * CarbonData SDK reader with pagination support
+ */
[e-mail]
[e-mail]
+public class PaginationCarbonReader<T> extends CarbonReader<T> {
+  // Splits based the file present in the reader path when the reader is built.
+  private List<InputSplit> allBlockletSplits;
+
+  // Rows till the current splits stored as list.
+  private List<Long> rowCountInSplits;
+
+  // Reader builder used to create the pagination reader, used for building split level readers.
+  private CarbonReaderBuilder readerBuilder;
+
+  private boolean isClosed;
+
+  // to store the rows of each blocklet in memory based LRU cache.
+  // key: unique blocklet id
+  // value: BlockletRows
+  private CarbonLRUCache cache =
+      new CarbonLRUCache(CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB,
+          CarbonCommonConstants.CARBON_MAX_PAGINATION_LRU_CACHE_SIZE_IN_MB_DEFAULT);
+
+  /**
+   * Call {@link #builder(String)} to construct an instance
+   */
+
+  PaginationCarbonReader(List<InputSplit> splits, CarbonReaderBuilder readerBuilder) {
+    // Initialize super class with no readers.
+    // Based on the splits identified for pagination query, readers will be built for the query.
+    super(null);
+    this.allBlockletSplits = splits;
+    this.readerBuilder = readerBuilder;
+    // prepare the mapping.
+    rowCountInSplits = new ArrayList<>(splits.size());
+    long sum = ((CarbonInputSplit) splits.get(0)).getDetailInfo().getRowCount();
+    rowCountInSplits.add(sum);
+    for (int i = 1; i < splits.size(); i++) {
+      // prepare a summation array of row counts in each blocklet,
+      // this is used for pruning with pagination vales.
+      // At current index, it contains sum of rows of all the blocklet from previous + current.
+      sum += ((CarbonInputSplit) splits.get(i)).getDetailInfo().getRowCount();
+      rowCountInSplits.add(sum);
+    }
+  }
+
+  /**
+   * Pagination query with from and to range.
+   *
+   * @param fromRowNumber must be greater 0 (as row id starts from 1)
+   *                      and less than equal to toRowNumber
+   * @param toRowNumber must be greater than 0 (as row id starts from 1)
+   *                and greater than equals to fromRowNumber and not outside the total rows
+   * @return array of rows between fromRowNumber and toRowNumber (inclusive)
+   * @throws Exception
+   */
+  public Object[] read(long fromRowNumber, long toRowNumber)
+      throws IOException, InterruptedException {
+    if (isClosed) {
+      throw new RuntimeException("Pagination Reader is closed. please build again");
+    }
+    if (fromRowNumber < 1) {
+      throw new IllegalArgumentException("from row id:" + fromRowNumber + " is less than 1");
+    }
+    if (fromRowNumber > toRowNumber) {
+      throw new IllegalArgumentException(
+          "from row id:" + fromRowNumber + " is greater than to row id:" + toRowNumber);
+    }
+    if (toRowNumber > getTotalRows()) {
+      throw new IllegalArgumentException(

Review comment:
       here why do we need to throw an exception, if the limit is crossed, cant we give till the last row?




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[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r434407280



##########
File path: docs/configuration-parameters.md
##########
@@ -141,6 +141,7 @@ This section provides the details of all the configurations required for the Car
 | carbon.load.all.segment.indexes.to.cache | true | Setting this configuration to false, will prune and load only matched segment indexes to cache using segment metadata information such as columnid and it's minmax values, which decreases the usage of driver memory.  |
 | carbon.secondary.index.creation.threads | 1 | Specifies the number of threads to concurrently process segments during secondary index creation. This property helps fine tuning the system when there are a lot of segments in a table. The value range is 1 to 50. |
 | carbon.si.lookup.partialstring | true | When true, it includes starts with, ends with and contains. When false, it includes only starts with secondary indexes. |
+| carbon.max.pagination.lru.cache.size.in.mb | -1 | Maximum memory **(in MB)** upto which the SDK pagination reader can cache the blocklet rows. Suggest to configure as multiple of blocklet size. Default value of -1 means there is no memory limit for caching. Only integer values greater than 0 are accepted. |

Review comment:
       multiple of blocklet means,
   N * blocklet size in mb. No need to give example




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ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r434408720



##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,41 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param fromRowNumber must be greater 0 (as row id starts from 1)
+*                      and less than equal to toRowNumber

Review comment:
       ok




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[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r434409645



##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,41 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param fromRowNumber must be greater 0 (as row id starts from 1)
+*                      and less than equal to toRowNumber
+* @param toRowNumber must be greater than 0 (as row id starts from 1)
+*                and greater than equals to fromRowNumber and not outside the total rows

Review comment:
       ok




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[GitBox]

ajantha-bhat commented on a change in pull request #3770:
URL: https://github.com/apache/carbondata/pull/3770#discussion_r434411308



##########
File path: docs/sdk-guide.md
##########
@@ -766,6 +771,41 @@ public VectorSchemaRoot getArrowVectors() throws IOException;
 public static ArrowRecordBatch byteArrayToArrowBatch(byte[] batchBytes, BufferAllocator bufferAllocator) throws IOException;
 ```
 
+### Class org.apache.carbondata.sdk.file.PaginationCarbonReader
+```
+/**
+* Pagination query with from and to range.
+*
+* @param fromRowNumber must be greater 0 (as row id starts from 1)
+*                      and less than equal to toRowNumber
+* @param toRowNumber must be greater than 0 (as row id starts from 1)
+*                and greater than equals to fromRowNumber and not outside the total rows
+* @return array of rows between fromRowNumber and toRowNumber (inclusive)
+* @throws Exception
+*/
+public Object[] read(long fromRowNumber, long toRowNumber) throws IOException, InterruptedException;
+```
+
+```
+/**
+* Get total rows in the folder or a list of CarbonData files.
+* It is based on the snapshot of files taken while building the reader.
+*
+* @return total rows from all the files in the reader.
+*/
+public long getTotalRows();
+```
+
+```
+/**
+* Closes the pagination reader, drops the cache and snapshot.
+* Need to build reader again if the files need to be read again.
+* Suggest to call this when new files are added in the folder.

Review comment:
       * call this when the all pagination queries are finished and can the drop cache.
   




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