org.apache.calcite.sql

Interface SqlSplittableAggFunction

All Known Implementing Classes:

SqlSplittableAggFunction.AbstractSumSplitter, SqlSplittableAggFunction.CountSplitter, SqlSplittableAggFunction.SelfSplitter, SqlSplittableAggFunction.Sum0Splitter, SqlSplittableAggFunction.SumSplitter

public interface SqlSplittableAggFunction

Aggregate function that can be split into partial aggregates.

For example, COUNT(x) can be split into COUNT(x) on subsets followed by SUM to combine those counts.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	SqlSplittableAggFunction.AbstractSumSplitter Common splitting strategy for SUM and SUM0 functions.
static class	SqlSplittableAggFunction.CountSplitter Splitting strategy for COUNT.
static interface	SqlSplittableAggFunction.Registry<E> Collection in which one can register an element.
static class	SqlSplittableAggFunction.SelfSplitter Aggregate function that splits into two applications of itself.
static class	SqlSplittableAggFunction.Sum0Splitter Splitting strategy for SUM0 function.
static class	SqlSplittableAggFunction.SumSplitter Splitting strategy for SUM function.

Method Summary

Modifier and Type	Method and Description
@Nullable AggregateCall	merge(AggregateCall top, AggregateCall bottom) Merge top and bottom aggregate calls into a single aggregate call, if they are legit to merge.
@Nullable 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.

Method Detail

split

AggregateCall split(AggregateCall aggregateCall,
                    Mappings.TargetMapping mapping)

other

@Nullable 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. Returns null if no aggregate is required.

topSplit

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.

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

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

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

Parameters:

rexBuilder - Rex builder

inputRowType - Input row type

aggregateCall - Aggregate call

Returns:

Expression for single row

merge

@Nullable AggregateCall merge(AggregateCall top,
                              AggregateCall bottom)

Merge top and bottom aggregate calls into a single aggregate call, if they are legit to merge.

SUM of SUM becomes SUM; SUM of COUNT becomes COUNT; MAX of MAX becomes MAX; MIN of MIN becomes MIN. AVG of AVG would not match, nor would COUNT of COUNT.

Parameters:

top - top aggregate call

bottom - bottom aggregate call

Returns:

Merged aggregate call, null if fails to merge aggregate calls