postgresql/src/include/executor/nodeAgg.h

/*-------------------------------------------------------------------------
 *
 * nodeAgg.h
 *	  prototypes for nodeAgg.c
 *
 *
 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/executor/nodeAgg.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef NODEAGG_H
#define NODEAGG_H

#include "nodes/execnodes.h"


/*
 * AggStatePerTransData - per aggregate state value information
 *
 * Working state for updating the aggregate's state value, by calling the
 * transition function with an input row. This struct does not store the
 * information needed to produce the final aggregate result from the transition
 * state, that's stored in AggStatePerAggData instead. This separation allows
 * multiple aggregate results to be produced from a single state value.
 */
typedef struct AggStatePerTransData
{
	/*
	 * These values are set up during ExecInitAgg() and do not change
	 * thereafter:
	 */

	/*
	 * Link to an Aggref expr this state value is for.
	 *
	 * There can be multiple Aggref's sharing the same state value, so long as
	 * the inputs and transition functions are identical and the final
	 * functions are not read-write.  This points to the first one of them.
	 */
	Aggref	   *aggref;

	/*
	 * Is this state value actually being shared by more than one Aggref?
	 */
	bool		aggshared;

	/*
	 * Number of aggregated input columns.  This includes ORDER BY expressions
	 * in both the plain-agg and ordered-set cases.  Ordered-set direct args
	 * are not counted, though.
	 */
	int			numInputs;

	/*
	 * Number of aggregated input columns to pass to the transfn.  This
	 * includes the ORDER BY columns for ordered-set aggs, but not for plain
	 * aggs.  (This doesn't count the transition state value!)
	 */
	int			numTransInputs;

	/* Oid of the state transition or combine function */
	Oid			transfn_oid;

	/* Oid of the serialization function or InvalidOid */
	Oid			serialfn_oid;

	/* Oid of the deserialization function or InvalidOid */
	Oid			deserialfn_oid;

	/* Oid of state value's datatype */
	Oid			aggtranstype;

	/*
	 * fmgr lookup data for transition function or combine function.  Note in
	 * particular that the fn_strict flag is kept here.
	 */
	FmgrInfo	transfn;

	/* fmgr lookup data for serialization function */
	FmgrInfo	serialfn;

	/* fmgr lookup data for deserialization function */
	FmgrInfo	deserialfn;

	/* Input collation derived for aggregate */
	Oid			aggCollation;

	/* number of sorting columns */
	int			numSortCols;

	/* number of sorting columns to consider in DISTINCT comparisons */
	/* (this is either zero or the same as numSortCols) */
	int			numDistinctCols;

	/* deconstructed sorting information (arrays of length numSortCols) */
	AttrNumber *sortColIdx;
	Oid		   *sortOperators;
	Oid		   *sortCollations;
	bool	   *sortNullsFirst;

	/*
	 * Comparators for input columns --- only set/used when aggregate has
	 * DISTINCT flag. equalfnOne version is used for single-column
	 * comparisons, equalfnMulti for the case of multiple columns.
	 */
	FmgrInfo	equalfnOne;
	ExprState  *equalfnMulti;

	/*
	 * initial value from pg_aggregate entry
	 */
	Datum		initValue;
	bool		initValueIsNull;

	/*
	 * We need the len and byval info for the agg's input and transition data
	 * types in order to know how to copy/delete values.
	 *
	 * Note that the info for the input type is used only when handling
	 * DISTINCT aggs with just one argument, so there is only one input type.
	 */
	int16		inputtypeLen,
				transtypeLen;
	bool		inputtypeByVal,
				transtypeByVal;

	/*
	 * Slots for holding the evaluated input arguments.  These are set up
	 * during ExecInitAgg() and then used for each input row requiring either
	 * FILTER or ORDER BY/DISTINCT processing.
	 */
	TupleTableSlot *sortslot;	/* current input tuple */
	TupleTableSlot *uniqslot;	/* used for multi-column DISTINCT */
	TupleDesc	sortdesc;		/* descriptor of input tuples */

	/*
	 * These values are working state that is initialized at the start of an
	 * input tuple group and updated for each input tuple.
	 *
	 * For a simple (non DISTINCT/ORDER BY) aggregate, we just feed the input
	 * values straight to the transition function.  If it's DISTINCT or
	 * requires ORDER BY, we pass the input values into a Tuplesort object;
	 * then at completion of the input tuple group, we scan the sorted values,
	 * eliminate duplicates if needed, and run the transition function on the
	 * rest.
	 *
	 * We need a separate tuplesort for each grouping set.
	 */

	Tuplesortstate **sortstates;	/* sort objects, if DISTINCT or ORDER BY */

	/*
	 * This field is a pre-initialized FunctionCallInfo struct used for
	 * calling this aggregate's transfn.  We save a few cycles per row by not
	 * re-initializing the unchanging fields; which isn't much, but it seems
	 * worth the extra space consumption.
	 */
	FunctionCallInfo transfn_fcinfo;

	/* Likewise for serialization and deserialization functions */
	FunctionCallInfo serialfn_fcinfo;

	FunctionCallInfo deserialfn_fcinfo;
}			AggStatePerTransData;

/*
 * AggStatePerAggData - per-aggregate information
 *
 * This contains the information needed to call the final function, to produce
 * a final aggregate result from the state value. If there are multiple
 * identical Aggrefs in the query, they can all share the same per-agg data.
 *
 * These values are set up during ExecInitAgg() and do not change thereafter.
 */
typedef struct AggStatePerAggData
{
	/*
	 * Link to an Aggref expr this state value is for.
	 *
	 * There can be multiple identical Aggref's sharing the same per-agg. This
	 * points to the first one of them.
	 */
	Aggref	   *aggref;

	/* index to the state value which this agg should use */
	int			transno;

	/* Optional Oid of final function (may be InvalidOid) */
	Oid			finalfn_oid;

	/*
	 * fmgr lookup data for final function --- only valid when finalfn_oid is
	 * not InvalidOid.
	 */
	FmgrInfo	finalfn;

	/*
	 * Number of arguments to pass to the finalfn.  This is always at least 1
	 * (the transition state value) plus any ordered-set direct args. If the
	 * finalfn wants extra args then we pass nulls corresponding to the
	 * aggregated input columns.
	 */
	int			numFinalArgs;

	/* ExprStates for any direct-argument expressions */
	List	   *aggdirectargs;

	/*
	 * We need the len and byval info for the agg's result data type in order
	 * to know how to copy/delete values.
	 */
	int16		resulttypeLen;
	bool		resulttypeByVal;

	/*
	 * "shareable" is false if this agg cannot share state values with other
	 * aggregates because the final function is read-write.
	 */
	bool		shareable;
}			AggStatePerAggData;

/*
 * AggStatePerGroupData - per-aggregate-per-group working state
 *
 * These values are working state that is initialized at the start of
 * an input tuple group and updated for each input tuple.
 *
 * In AGG_PLAIN and AGG_SORTED modes, we have a single array of these
 * structs (pointed to by aggstate->pergroup); we re-use the array for
 * each input group, if it's AGG_SORTED mode.  In AGG_HASHED mode, the
 * hash table contains an array of these structs for each tuple group.
 *
 * Logically, the sortstate field belongs in this struct, but we do not
 * keep it here for space reasons: we don't support DISTINCT aggregates
 * in AGG_HASHED mode, so there's no reason to use up a pointer field
 * in every entry of the hashtable.
 */
typedef struct AggStatePerGroupData
{
#define FIELDNO_AGGSTATEPERGROUPDATA_TRANSVALUE 0
	Datum		transValue;		/* current transition value */
#define FIELDNO_AGGSTATEPERGROUPDATA_TRANSVALUEISNULL 1
	bool		transValueIsNull;

#define FIELDNO_AGGSTATEPERGROUPDATA_NOTRANSVALUE 2
	bool		noTransValue;	/* true if transValue not set yet */

	/*
	 * Note: noTransValue initially has the same value as transValueIsNull,
	 * and if true both are cleared to false at the same time.  They are not
	 * the same though: if transfn later returns a NULL, we want to keep that
	 * NULL and not auto-replace it with a later input value. Only the first
	 * non-NULL input will be auto-substituted.
	 */
}			AggStatePerGroupData;

/*
 * AggStatePerPhaseData - per-grouping-set-phase state
 *
 * Grouping sets are divided into "phases", where a single phase can be
 * processed in one pass over the input. If there is more than one phase, then
 * at the end of input from the current phase, state is reset and another pass
 * taken over the data which has been re-sorted in the mean time.
 *
 * Accordingly, each phase specifies a list of grouping sets and group clause
 * information, plus each phase after the first also has a sort order.
 */
typedef struct AggStatePerPhaseData
{
	AggStrategy aggstrategy;	/* strategy for this phase */
	int			numsets;		/* number of grouping sets (or 0) */
	int		   *gset_lengths;	/* lengths of grouping sets */
	Bitmapset **grouped_cols;	/* column groupings for rollup */
	ExprState **eqfunctions;	/* expression returning equality, indexed by
								 * nr of cols to compare */
	Agg		   *aggnode;		/* Agg node for phase data */
	Sort	   *sortnode;		/* Sort node for input ordering for phase */

	ExprState  *evaltrans;		/* evaluation of transition functions  */
}			AggStatePerPhaseData;

/*
 * AggStatePerHashData - per-hashtable state
 *
 * When doing grouping sets with hashing, we have one of these for each
 * grouping set. (When doing hashing without grouping sets, we have just one of
 * them.)
 */
typedef struct AggStatePerHashData
{
	TupleHashTable hashtable;	/* hash table with one entry per group */
	TupleHashIterator hashiter; /* for iterating through hash table */
	TupleTableSlot *hashslot;	/* slot for loading hash table */
	FmgrInfo   *hashfunctions;	/* per-grouping-field hash fns */
	Oid		   *eqfuncoids;		/* per-grouping-field equality fns */
	int			numCols;		/* number of hash key columns */
	int			numhashGrpCols; /* number of columns in hash table */
	int			largestGrpColIdx;	/* largest col required for hashing */
	AttrNumber *hashGrpColIdxInput; /* hash col indices in input slot */
	AttrNumber *hashGrpColIdxHash;	/* indices in hashtbl tuples */
	Agg		   *aggnode;		/* original Agg node, for numGroups etc. */
}			AggStatePerHashData;


extern AggState *ExecInitAgg(Agg *node, EState *estate, int eflags);
extern void ExecEndAgg(AggState *node);
extern void ExecReScanAgg(AggState *node);

extern Size hash_agg_entry_size(int numAggs);

extern Datum aggregate_dummy(PG_FUNCTION_ARGS);

#endif							/* NODEAGG_H */