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Add string_agg aggregate functions. The one argument version concatenates

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the input values into a string. The two argument version also does the same
thing, but inserts delimiters between elements.

Original patch by Pavel Stehule, reviewed by David E. Wheeler and me.
This commit is contained in:
Itagaki Takahiro
2010-02-01 03:14:45 +00:00
parent ee3a81f0a0
commit 9ea9918e37
8 changed files with 193 additions and 7 deletions
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106
src/backend/utils/adt/varlena.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.174 2010/01/25 20:55:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.175 2010/02/01 03:14:43 itagaki Exp $
*
*-------------------------------------------------------------------------
*/
@ -21,6 +21,7 @@
#include "libpq/md5.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "nodes/execnodes.h"
#include "parser/scansup.h"
#include "regex/regex.h"
#include "utils/builtins.h"
@ -73,6 +74,7 @@ static bytea *bytea_substring(Datum str,
int L,
bool length_not_specified);
static bytea *bytea_overlay(bytea *t1, bytea *t2, int sp, int sl);
static StringInfo makeStringAggState(fmNodePtr context);
/*****************************************************************************
@ -3315,3 +3317,105 @@ pg_column_size(PG_FUNCTION_ARGS)
PG_RETURN_INT32(result);
}
/*
* string_agg - Concatenates values and returns string.
*
* Syntax: string_agg(value text, delimiter text = '') RETURNS text
*
* Note: Any NULL values are ignored. The first-call delimiter isn't
* actually used at all, and on subsequent calls the delimiter precedes
* the associated value.
*/
static StringInfo
makeStringAggState(fmNodePtr context)
{
StringInfo state;
MemoryContext aggcontext;
MemoryContext oldcontext;
if (context && IsA(context, AggState))
aggcontext = ((AggState *) context)->aggcontext;
else if (context && IsA(context, WindowAggState))
aggcontext = ((WindowAggState *) context)->wincontext;
else
{
/* cannot be called directly because of internal-type argument */
elog(ERROR, "string_agg_transfn called in non-aggregate context");
aggcontext = NULL; /* keep compiler quiet */
}
/* Create state in aggregate context */
oldcontext = MemoryContextSwitchTo(aggcontext);
state = makeStringInfo();
MemoryContextSwitchTo(oldcontext);
return state;
}
Datum
string_agg_transfn(PG_FUNCTION_ARGS)
{
StringInfo state;
state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
/* Append the element unless not null. */
if (!PG_ARGISNULL(1))
{
if (state == NULL)
state = makeStringAggState(fcinfo->context);
appendStringInfoText(state, PG_GETARG_TEXT_PP(1)); /* value */
}
/*
* The transition type for string_agg() is declared to be "internal", which
* is a pass-by-value type the same size as a pointer.
*/
PG_RETURN_POINTER(state);
}
Datum
string_agg_delim_transfn(PG_FUNCTION_ARGS)
{
StringInfo state;
state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
/* Append the value unless not null. */
if (!PG_ARGISNULL(1))
{
if (state == NULL)
state = makeStringAggState(fcinfo->context);
else if (!PG_ARGISNULL(2))
appendStringInfoText(state, PG_GETARG_TEXT_PP(2)); /* delimiter */
appendStringInfoText(state, PG_GETARG_TEXT_PP(1)); /* value */
}
/*
* The transition type for string_agg() is declared to be "internal", which
* is a pass-by-value type the same size as a pointer.
*/
PG_RETURN_POINTER(state);
}
Datum
string_agg_finalfn(PG_FUNCTION_ARGS)
{
StringInfo state;
if (PG_ARGISNULL(0))
PG_RETURN_NULL();
/* cannot be called directly because of internal-type argument */
Assert(fcinfo->context &&
(IsA(fcinfo->context, AggState) ||
IsA(fcinfo->context, WindowAggState)));
state = (StringInfo) PG_GETARG_POINTER(0);
if (state != NULL)
PG_RETURN_TEXT_P(cstring_to_text(state->data));
else
PG_RETURN_NULL();
}