org.apache.drill.exec.planner.physical

Class ConvertCountToDirectScanPrule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.drill.exec.planner.physical.Prule

org.apache.drill.exec.planner.physical.ConvertCountToDirectScanPrule

public class ConvertCountToDirectScanPrule
extends Prule

This rule will convert " select count(*) as mycount from table " or " select count(not-nullable-expr) as mycount from table " into

    Project(mycount)
         \
    DirectGroupScan ( PojoRecordReader ( rowCount ))

or " select count(column) as mycount from table " into

      Project(mycount)
           \
            DirectGroupScan (PojoRecordReader (columnValueCount))

Rule can be applied if query contains multiple count expressions. " select count(column1), count(column2), count(*) from table "

Currently, only parquet group scan has the exact row count and column value count, obtained from parquet row group info. This will save the cost to scan the whole parquet files.

NOTE: This rule is a physical planning counterpart to a similar ConvertCountToDirectScanRule logical rule. However, while the logical rule relies on the Parquet metadata cache's Summary aggregates, this rule is applicable if the exact row count is available from the GroupScan regardless of where that stat came from. Hence, it is more general, with the trade-off that the GroupScan relies on the fully expanded list of row groups to compute the aggregate row count.

Field Summary

Fields

Modifier and Type	Field and Description
static org.apache.calcite.plan.RelOptRule	AGG_ON_PROJ_ON_SCAN
static org.apache.calcite.plan.RelOptRule	AGG_ON_SCAN

Fields inherited from class org.apache.calcite.plan.RelOptRule

description, operands, relBuilderFactory

Method Summary

Modifier and Type	Method and Description
void	onMatch(org.apache.calcite.plan.RelOptRuleCall call)

Methods inherited from class org.apache.drill.exec.planner.physical.Prule

convert, isSingleMode

Methods inherited from class org.apache.calcite.plan.RelOptRule

any, convert, convertList, convertOperand, convertOperand, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, none, operand, operand, operand, operand, operand, operandJ, operandJ, some, toString, unordered

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

AGG_ON_PROJ_ON_SCAN

public static final org.apache.calcite.plan.RelOptRule AGG_ON_PROJ_ON_SCAN

AGG_ON_SCAN

public static final org.apache.calcite.plan.RelOptRule AGG_ON_SCAN

Method Detail

onMatch

public void onMatch(org.apache.calcite.plan.RelOptRuleCall call)

Specified by:

onMatch in class org.apache.calcite.plan.RelOptRule