array's subscripts.
Pavel Stehule, some editorialization by me.
-<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.65 2008/04/27 04:33:27 alvherre Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.66 2008/04/28 14:48:57 alvherre Exp $ -->
<sect1 id="arrays">
<title>Arrays</title>
</para>
+ <para>
+ Alternatively, the <function>generate_subscripts</> function can be used.
+ For example:
+
+<programlisting>
+SELECT * FROM
+ (SELECT pay_by_quarter,
+ generate_subscripts(pay_by_quarter, 1) AS s
+ FROM sal_emp) AS foo
+ WHERE pay_by_quarter[s] = 10000;
+</programlisting>
+
+ This function is described in <xref linkend="functions-srf-subscripts">.
+ </para>
+
<tip>
<para>
Arrays are not sets; searching for specific array elements
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.433 2008/04/17 20:56:41 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.434 2008/04/28 14:48:57 alvherre Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
<para>
This section describes functions that possibly return more than one row.
Currently the only functions in this class are series generating functions,
- as detailed in <xref linkend="functions-srf-series">.
+ as detailed in <xref linkend="functions-srf-series"> and
+ <xref linkend="functions-srf-subscripts">.
</para>
<table id="functions-srf-series">
(3 rows)
</programlisting>
</para>
+
+ <table id="functions-srf-subscripts">
+
+ <indexterm>
+ <primary>generate_subscripts</primary>
+ </indexterm>
+
+ <title>Subscripts Generating Functions</title>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Function</entry>
+ <entry>Return Type</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry><literal><function>generate_subscripts</function>(<parameter>array annyarray</parameter>, <parameter>dim int</parameter>)</literal></entry>
+ <entry><type>setof int</type></entry>
+ <entry>
+ Generate a series comprising the given array's subscripts.
+ </entry>
+ </row>
+
+ <row>
+ <entry><literal><function>generate_subscripts</function>(<parameter>array annyarray</parameter>, <parameter>dim int</parameter>, <parameter>reverse boolean</parameter>)</literal></entry>
+ <entry><type>setof int</type></entry>
+ <entry>
+ Generate a series comprising the given array's subscripts. When
+ <parameter>reverse</parameter> is true, the series is returned in
+ reverse order.
+ </entry>
+ </row>
+
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>
+ Zero rows are returned for arrays that do not have the requested dimension,
+ or for NULL arrays (but valid subscripts are returned for NULL array
+ elements.) Some examples follow:
+<programlisting>
+-- basic usage
+select generate_subscripts('{NULL,1,NULL,2}'::int[], 1) as s;
+ s
+---
+ 1
+ 2
+ 3
+ 4
+(4 rows)
+
+-- presenting an array, the subscript and the subscripted
+-- value requires a subquery
+select * from arrays;
+ a
+--------------------
+ {-1,-2}
+ {100,200}
+(2 rows)
+
+select a as array, s as subscript, a[s] as value
+from (select generate_subscripts(a, 1) as s, a from arrays) foo;
+ array | subscript | value
+-----------+-----------+-------
+ {-1,-2} | 1 | -1
+ {-1,-2} | 2 | -2
+ {100,200} | 1 | 100
+ {100,200} | 2 | 200
+(4 rows)
+
+-- unnest a 2D array
+create or replace function unnest2(anyarray)
+returns setof anyelement as $$
+select $1[i][j]
+ from generate_subscripts($1,1) g1(i),
+ generate_subscripts($1,2) g2(j);
+$$ language sql immutable;
+CREATE FUNCTION
+postgres=# select * from unnest2(array[[1,2],[3,4]]);
+ unnest2
+---------
+ 1
+ 2
+ 3
+ 4
+(4 rows)
+</programlisting>
+ </para>
+
</sect1>
<sect1 id="functions-info">
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.143 2008/04/11 22:52:05 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.144 2008/04/28 14:48:57 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
#include <ctype.h>
#include "access/tupmacs.h"
+#include "funcapi.h"
#include "libpq/pqformat.h"
#include "parser/parse_coerce.h"
#include "utils/array.h"
PG_RETURN_ARRAYTYPE_P(result);
}
+
+
+typedef struct generate_subscripts_fctx
+{
+ int4 lower;
+ int4 upper;
+ bool reverse;
+} generate_subscripts_fctx;
+
+/*
+ * generate_subscripts(array anyarray, dim int [, reverse bool])
+ * Returns all subscripts of the array for any dimension
+ */
+Datum
+generate_subscripts(PG_FUNCTION_ARGS)
+{
+ FuncCallContext *funcctx;
+ MemoryContext oldcontext;
+ generate_subscripts_fctx *fctx;
+
+ /* stuff done only on the first call of the function */
+ if (SRF_IS_FIRSTCALL())
+ {
+ ArrayType *v = PG_GETARG_ARRAYTYPE_P(0);
+ int reqdim = PG_GETARG_INT32(1);
+ int *lb,
+ *dimv;
+
+ /* create a function context for cross-call persistence */
+ funcctx = SRF_FIRSTCALL_INIT();
+
+ /* Sanity check: does it look like an array at all? */
+ if (ARR_NDIM(v) <= 0 || ARR_NDIM(v) > MAXDIM)
+ SRF_RETURN_DONE(funcctx);
+
+ /* Sanity check: was the requested dim valid */
+ if (reqdim <= 0 || reqdim > ARR_NDIM(v))
+ SRF_RETURN_DONE(funcctx);
+
+ /*
+ * switch to memory context appropriate for multiple function calls
+ */
+ oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+ fctx = (generate_subscripts_fctx *) palloc(sizeof(generate_subscripts_fctx));
+
+ lb = ARR_LBOUND(v);
+ dimv = ARR_DIMS(v);
+
+ fctx->lower = lb[reqdim - 1];
+ fctx->upper = dimv[reqdim - 1] + lb[reqdim - 1] - 1;
+ fctx->reverse = (PG_NARGS() < 3) ? false : PG_GETARG_BOOL(2);
+
+ funcctx->user_fctx = fctx;
+
+ MemoryContextSwitchTo(oldcontext);
+ }
+
+ funcctx = SRF_PERCALL_SETUP();
+
+ fctx = funcctx->user_fctx;
+
+ if (fctx->lower <= fctx->upper)
+ {
+ if (!fctx->reverse)
+ SRF_RETURN_NEXT(funcctx, Int32GetDatum(fctx->lower++));
+ else
+ SRF_RETURN_NEXT(funcctx, Int32GetDatum(fctx->upper--));
+ }
+ else
+ /* done when there are no more elements left */
+ SRF_RETURN_DONE(funcctx);
+}
+
+/*
+ * generate_subscripts_nodir
+ * Implements the 2-argument version of generate_subscripts
+ */
+Datum
+generate_subscripts_nodir(PG_FUNCTION_ARGS)
+{
+ /* just call the other one -- it can handle both cases */
+ return generate_subscripts(fcinfo);
+}
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.492 2008/04/17 20:56:41 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.493 2008/04/28 14:48:57 alvherre Exp $
*
* NOTES
* The script catalog/genbki.sh reads this file and generates .bki
DESCR("larger of two");
DATA(insert OID = 516 ( array_smaller PGNSP PGUID 12 1 0 f f t f i 2 2277 "2277 2277" _null_ _null_ _null_ array_smaller - _null_ _null_ ));
DESCR("smaller of two");
+DATA(insert OID = 1191 ( generate_subscripts PGNSP PGUID 12 1 1000 f f t t v 3 23 "2277 23 16" _null_ _null_ _null_ generate_subscripts - _null_ _null_ ));
+DESCR("array subscripts generator");
+DATA(insert OID = 1192 ( generate_subscripts PGNSP PGUID 12 1 1000 f f t t v 2 23 "2277 23" _null_ _null_ _null_ generate_subscripts_nodir - _null_ _null_ ));
+DESCR("array subscripts generator");
+
DATA(insert OID = 760 ( smgrin PGNSP PGUID 12 1 0 f f t f s 1 210 "2275" _null_ _null_ _null_ smgrin - _null_ _null_ ));
DESCR("I/O");
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/utils/array.h,v 1.66 2008/01/01 19:45:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/array.h,v 1.67 2008/04/28 14:48:57 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
extern Datum array_upper(PG_FUNCTION_ARGS);
extern Datum array_larger(PG_FUNCTION_ARGS);
extern Datum array_smaller(PG_FUNCTION_ARGS);
+extern Datum generate_subscripts(PG_FUNCTION_ARGS);
+extern Datum generate_subscripts_nodir(PG_FUNCTION_ARGS);
extern Datum array_ref(ArrayType *array, int nSubscripts, int *indx,
int arraytyplen, int elmlen, bool elmbyval, char elmalign,
drop type _comptype;
drop table comptable;
drop type comptype;
+create or replace function unnest1(anyarray)
+returns setof anyelement as $$
+select $1[s] from generate_subscripts($1,1) g(s);
+$$ language sql immutable;
+create or replace function unnest2(anyarray)
+returns setof anyelement as $$
+select $1[s1][s2] from generate_subscripts($1,1) g1(s1),
+ generate_subscripts($1,2) g2(s2);
+$$ language sql immutable;
+select * from unnest1(array[1,2,3]);
+ unnest1
+---------
+ 1
+ 2
+ 3
+(3 rows)
+
+select * from unnest2(array[[1,2,3],[4,5,6]]);
+ unnest2
+---------
+ 1
+ 2
+ 3
+ 4
+ 5
+ 6
+(6 rows)
+
+drop function unnest1(anyarray);
+drop function unnest2(anyarray);
drop type _comptype;
drop table comptable;
drop type comptype;
+
+create or replace function unnest1(anyarray)
+returns setof anyelement as $$
+select $1[s] from generate_subscripts($1,1) g(s);
+$$ language sql immutable;
+
+create or replace function unnest2(anyarray)
+returns setof anyelement as $$
+select $1[s1][s2] from generate_subscripts($1,1) g1(s1),
+ generate_subscripts($1,2) g2(s2);
+$$ language sql immutable;
+
+select * from unnest1(array[1,2,3]);
+select * from unnest2(array[[1,2,3],[4,5,6]]);
+
+drop function unnest1(anyarray);
+drop function unnest2(anyarray);
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