org.apache.calcite.sql

Class SqlSplittableAggFunction.CountSplitter

java.lang.Object

org.apache.calcite.sql.SqlSplittableAggFunction.CountSplitter

All Implemented Interfaces:

SqlSplittableAggFunction

Enclosing interface:

SqlSplittableAggFunction

public static class SqlSplittableAggFunction.CountSplitter
extends Object
implements SqlSplittableAggFunction

Splitting strategy for COUNT.

COUNT splits into itself followed by SUM. (Actually SUM0, because the total needs to be 0, not null, if there are 0 rows.) This rule works for any number of arguments to COUNT, including COUNT(*).

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.calcite.sql.SqlSplittableAggFunction

SqlSplittableAggFunction.AbstractSumSplitter, SqlSplittableAggFunction.CountSplitter, SqlSplittableAggFunction.Registry<E>, SqlSplittableAggFunction.SelfSplitter, SqlSplittableAggFunction.Sum0Splitter, SqlSplittableAggFunction.SumSplitter

Field Summary

Fields

Modifier and Type	Field and Description
static SqlSplittableAggFunction.CountSplitter	INSTANCE

Constructor Summary

Constructors

Constructor and Description
CountSplitter()

Method Summary

Modifier and Type	Method and Description
AggregateCall	other(RelDataTypeFactory typeFactory, AggregateCall e) Called to generate an aggregate for the other side of the join than the side aggregate call's arguments come from.
RexNode	singleton(RexBuilder rexBuilder, RelDataType inputRowType, AggregateCall aggregateCall) Generates an expression for the value of the aggregate function when applied to a single row.
AggregateCall	split(AggregateCall aggregateCall, Mappings.TargetMapping mapping)
AggregateCall	topSplit(RexBuilder rexBuilder, SqlSplittableAggFunction.Registry<RexNode> extra, int offset, RelDataType inputRowType, AggregateCall aggregateCall, int leftSubTotal, int rightSubTotal) Generates an aggregate call to merge sub-totals.

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final SqlSplittableAggFunction.CountSplitter INSTANCE

Constructor Detail

CountSplitter

public CountSplitter()

Method Detail

split

public AggregateCall split(AggregateCall aggregateCall,
                           Mappings.TargetMapping mapping)

Specified by:

split in interface SqlSplittableAggFunction

other

public AggregateCall other(RelDataTypeFactory typeFactory,
                           AggregateCall e)

Description copied from interface: SqlSplittableAggFunction

Called to generate an aggregate for the other side of the join than the side aggregate call's arguments come from. Returns null if no aggregate is required.

Specified by:

other in interface SqlSplittableAggFunction

topSplit

public AggregateCall topSplit(RexBuilder rexBuilder,
                              SqlSplittableAggFunction.Registry<RexNode> extra,
                              int offset,
                              RelDataType inputRowType,
                              AggregateCall aggregateCall,
                              int leftSubTotal,
                              int rightSubTotal)

Description copied from interface: SqlSplittableAggFunction

Generates an aggregate call to merge sub-totals.

Most implementations will add a single aggregate call to aggCalls, and return a RexInputRef that points to it.

Specified by:

topSplit in interface SqlSplittableAggFunction

Parameters:

rexBuilder - Rex builder

extra - Place to define extra input expressions

offset - Offset due to grouping columns (and indicator columns if applicable)

inputRowType - Input row type

aggregateCall - Source aggregate call

leftSubTotal - Ordinal of the sub-total coming from the left side of the join, or -1 if there is no such sub-total

rightSubTotal - Ordinal of the sub-total coming from the right side of the join, or -1 if there is no such sub-total

Returns:

Aggregate call

singleton

public RexNode singleton(RexBuilder rexBuilder,
                         RelDataType inputRowType,
                         AggregateCall aggregateCall)

Generates an expression for the value of the aggregate function when applied to a single row.

For example, if there is one row:

• SUM(x) is x
• MIN(x) is x
• MAX(x) is x
• COUNT(x) is CASE WHEN x IS NOT NULL THEN 1 ELSE 0 END 1 which can be simplified to 1 if x is never null
• COUNT(*) is 1

COUNT(*), and COUNT applied to all NOT NULL arguments, become 1; otherwise CASE WHEN arg0 IS NOT NULL THEN 1 ELSE 0 END.

Specified by:

singleton in interface SqlSplittableAggFunction

Parameters:

rexBuilder - Rex builder

inputRowType - Input row type

aggregateCall - Aggregate call

Returns:

Expression for single row