Github user jackylk commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/1510#discussion_r156602474
--- Diff: core/src/main/java/org/apache/carbondata/core/datamap/DataMapChooser.java ---
@@ -0,0 +1,269 @@
+/*
+ * 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.core.datamap;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.apache.carbondata.core.datamap.dev.expr.AndDataMapExprWrapper;
+import org.apache.carbondata.core.datamap.dev.expr.DataMapExprWrapper;
+import org.apache.carbondata.core.datamap.dev.expr.DataMapExprWrapperImpl;
+import org.apache.carbondata.core.datamap.dev.expr.OrDataMapExprWrapper;
+import org.apache.carbondata.core.metadata.schema.table.CarbonTable;
+import org.apache.carbondata.core.scan.expression.ColumnExpression;
+import org.apache.carbondata.core.scan.expression.Expression;
+import org.apache.carbondata.core.scan.expression.logical.AndExpression;
+import org.apache.carbondata.core.scan.expression.logical.OrExpression;
+import org.apache.carbondata.core.scan.filter.intf.ExpressionType;
+import org.apache.carbondata.core.scan.filter.resolver.FilterResolverIntf;
+import org.apache.carbondata.core.scan.filter.resolver.resolverinfo.TrueConditionalResolverImpl;
+
+/**
+ * This chooser does 2 jobs.
+ * 1. Based on filter expression it converts the available datamaps to datamap expression.
+ * For example, there are 2 datamaps available on table1
+ * Datamap1 : column1
+ * Datamap2 : column2
+ * Query: select * from table1 where column1 ='a' and column2 =b
+ * For the above query, we create datamap expression as AndDataMapExpression(Datamap1, DataMap2).
+ * So for the above query both the datamaps are included and the output of them will be
+ * applied AND condition to improve the performance
+ *
+ * 2. It chooses the datamap out of available datamaps based on simple logic.
+ * Like if there is filter condition on column1 then for
+ * supposing 2 datamaps(1. column1 2. column1+column2) are supporting this column then we choose
+ * the datamap which has fewer columns that is the first datamap.
+ */
+public class DataMapChooser {
+
+ public DataMapExprWrapper choose(CarbonTable carbonTable,
+ FilterResolverIntf resolverIntf) {
+ if (resolverIntf != null) {
+ Expression expression = resolverIntf.getFilterExpression();
+ // First check for FG datamaps if any exist
+ List<TableDataMap> allDataMapFG =
+ DataMapStoreManager.getInstance().getAllDataMap(carbonTable, DataMapType.FG);
+ ExpressionTuple tuple = selectDataMap(expression, allDataMapFG);
+ if (tuple.dataMapExprWrapper == null) {
+ // Check for CG datamap
+ List<TableDataMap> allDataMapCG =
+ DataMapStoreManager.getInstance().getAllDataMap(carbonTable, DataMapType.CG);
+ tuple = selectDataMap(expression, allDataMapCG);
+ }
+ if (tuple.dataMapExprWrapper != null) {
+ return tuple.dataMapExprWrapper;
+ }
+ }
+ // Return the default datamap if no other datamap exists.
+ return new DataMapExprWrapperImpl(DataMapStoreManager.getInstance()
--- End diff --
make the line wrap easier to read, like:
```
return new DataMapExprWrapperImpl(
DataMapStoreManager.getInstance().getDefaultDataMap(
carbonTable.getAbsoluteTableIdentifier()), resolverIntf);
```
---
Locked
