org.apache.drill.exec.planner.common

Class CountToDirectScanUtils

java.lang.Object

org.apache.drill.exec.planner.common.CountToDirectScanUtils

public class CountToDirectScanUtils
extends Object

A utility class that contains helper functions used by rules that convert COUNT(*) and COUNT(col) aggregates (no group-by) to DirectScan

Constructor Summary

Constructors

Constructor and Description
CountToDirectScanUtils()

Method Summary

Modifier and Type	Method and Description
static LinkedHashMap<String,Class<?>>	buildSchema(List<String> fieldNames) Builds schema based on given field names.
static org.apache.calcite.rel.type.RelDataType	constructDataType(org.apache.calcite.rel.core.Aggregate aggregateRel, Collection<String> fieldNames) For each aggregate call creates field based on its name with bigint type.
static boolean	containsStarOrNotNullInput(org.apache.calcite.rel.core.AggregateCall aggregateCall, org.apache.calcite.rel.core.Aggregate aggregate) Checks if aggregate call contains star or non-null expression:
static List<org.apache.calcite.rex.RexNode>	prepareFieldExpressions(org.apache.calcite.rel.type.RelDataType rowType) For each field creates row expression.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CountToDirectScanUtils

public CountToDirectScanUtils()

Method Detail

containsStarOrNotNullInput

public static boolean containsStarOrNotNullInput(org.apache.calcite.rel.core.AggregateCall aggregateCall,
                                                 org.apache.calcite.rel.core.Aggregate aggregate)

Checks if aggregate call contains star or non-null expression:

 count(*)  == >  empty arg  ==>  rowCount
 count(Not-null-input) ==> rowCount
 

Parameters:

aggregateCall - aggregate call

aggregate - aggregate relation expression

Returns:

true of aggregate call contains star or non-null expression

constructDataType

public static org.apache.calcite.rel.type.RelDataType constructDataType(org.apache.calcite.rel.core.Aggregate aggregateRel,
                                                                        Collection<String> fieldNames)

For each aggregate call creates field based on its name with bigint type. Constructs record type for created fields.

Parameters:

aggregateRel - aggregate relation expression

fieldNames - field names

Returns:

record type

buildSchema

public static LinkedHashMap<String,Class<?>> buildSchema(List<String> fieldNames)

Builds schema based on given field names. Type for each schema is set to long.class.

Parameters:

fieldNames - field names

Returns:

schema

prepareFieldExpressions

public static List<org.apache.calcite.rex.RexNode> prepareFieldExpressions(org.apache.calcite.rel.type.RelDataType rowType)

For each field creates row expression.

Parameters:

rowType - row type

Returns:

list of row expressions