Add generate_subscripts, a series-generation function which generates an
array's subscripts. Pavel Stehule, some editorialization by me.
This commit is contained in:
Alvaro Herrera
parent
a1d479f518
commit
1fcb977a13
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@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.65 2008/04/27 04:33:27 alvherre Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/array.sgml,v 1.66 2008/04/28 14:48:57 alvherre Exp $ -->
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<sect1 id="arrays">
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<title>Arrays</title>
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@ -542,6 +542,21 @@ SELECT * FROM sal_emp WHERE 10000 = ALL (pay_by_quarter);
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</para>
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<para>
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Alternatively, the <function>generate_subscripts</> function can be used.
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For example:
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<programlisting>
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SELECT * FROM
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(SELECT pay_by_quarter,
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generate_subscripts(pay_by_quarter, 1) AS s
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FROM sal_emp) AS foo
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WHERE pay_by_quarter[s] = 10000;
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</programlisting>
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This function is described in <xref linkend="functions-srf-subscripts">.
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</para>
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<tip>
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<para>
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Arrays are not sets; searching for specific array elements
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@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.433 2008/04/17 20:56:41 momjian Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.434 2008/04/28 14:48:57 alvherre Exp $ -->
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<chapter id="functions">
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<title>Functions and Operators</title>
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@ -10613,7 +10613,8 @@ AND
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<para>
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This section describes functions that possibly return more than one row.
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Currently the only functions in this class are series generating functions,
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as detailed in <xref linkend="functions-srf-series">.
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as detailed in <xref linkend="functions-srf-series"> and
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<xref linkend="functions-srf-subscripts">.
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</para>
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<table id="functions-srf-series">
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@ -10691,6 +10692,99 @@ select current_date + s.a as dates from generate_series(0,14,7) as s(a);
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(3 rows)
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</programlisting>
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</para>
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<table id="functions-srf-subscripts">
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<indexterm>
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<primary>generate_subscripts</primary>
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</indexterm>
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<title>Subscripts Generating Functions</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Function</entry>
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<entry>Return Type</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><literal><function>generate_subscripts</function>(<parameter>array annyarray</parameter>, <parameter>dim int</parameter>)</literal></entry>
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<entry><type>setof int</type></entry>
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<entry>
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Generate a series comprising the given array's subscripts.
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</entry>
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</row>
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<row>
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<entry><literal><function>generate_subscripts</function>(<parameter>array annyarray</parameter>, <parameter>dim int</parameter>, <parameter>reverse boolean</parameter>)</literal></entry>
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<entry><type>setof int</type></entry>
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<entry>
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Generate a series comprising the given array's subscripts. When
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<parameter>reverse</parameter> is true, the series is returned in
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reverse order.
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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Zero rows are returned for arrays that do not have the requested dimension,
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or for NULL arrays (but valid subscripts are returned for NULL array
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elements.) Some examples follow:
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<programlisting>
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-- basic usage
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select generate_subscripts('{NULL,1,NULL,2}'::int[], 1) as s;
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s
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---
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1
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2
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3
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4
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(4 rows)
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-- presenting an array, the subscript and the subscripted
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-- value requires a subquery
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select * from arrays;
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a
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--------------------
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{-1,-2}
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{100,200}
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(2 rows)
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select a as array, s as subscript, a[s] as value
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from (select generate_subscripts(a, 1) as s, a from arrays) foo;
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array | subscript | value
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-----------+-----------+-------
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{-1,-2} | 1 | -1
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{-1,-2} | 2 | -2
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{100,200} | 1 | 100
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{100,200} | 2 | 200
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(4 rows)
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-- unnest a 2D array
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create or replace function unnest2(anyarray)
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returns setof anyelement as $$
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select $1[i][j]
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from generate_subscripts($1,1) g1(i),
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generate_subscripts($1,2) g2(j);
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$$ language sql immutable;
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CREATE FUNCTION
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postgres=# select * from unnest2(array[[1,2],[3,4]]);
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unnest2
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---------
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1
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2
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3
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4
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(4 rows)
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</programlisting>
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</para>
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</sect1>
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<sect1 id="functions-info">
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.143 2008/04/11 22:52:05 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/utils/adt/arrayfuncs.c,v 1.144 2008/04/28 14:48:57 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -17,6 +17,7 @@
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#include <ctype.h>
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#include "access/tupmacs.h"
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#include "funcapi.h"
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#include "libpq/pqformat.h"
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#include "parser/parse_coerce.h"
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#include "utils/array.h"
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@ -4231,3 +4232,86 @@ array_smaller(PG_FUNCTION_ARGS)
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PG_RETURN_ARRAYTYPE_P(result);
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}
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typedef struct generate_subscripts_fctx
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{
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int4 lower;
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int4 upper;
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bool reverse;
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} generate_subscripts_fctx;
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/*
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* generate_subscripts(array anyarray, dim int [, reverse bool])
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* Returns all subscripts of the array for any dimension
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*/
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Datum
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generate_subscripts(PG_FUNCTION_ARGS)
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{
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FuncCallContext *funcctx;
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MemoryContext oldcontext;
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generate_subscripts_fctx *fctx;
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/* stuff done only on the first call of the function */
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if (SRF_IS_FIRSTCALL())
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{
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ArrayType *v = PG_GETARG_ARRAYTYPE_P(0);
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int reqdim = PG_GETARG_INT32(1);
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int *lb,
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*dimv;
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/* create a function context for cross-call persistence */
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funcctx = SRF_FIRSTCALL_INIT();
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/* Sanity check: does it look like an array at all? */
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if (ARR_NDIM(v) <= 0 || ARR_NDIM(v) > MAXDIM)
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SRF_RETURN_DONE(funcctx);
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/* Sanity check: was the requested dim valid */
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if (reqdim <= 0 || reqdim > ARR_NDIM(v))
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SRF_RETURN_DONE(funcctx);
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/*
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* switch to memory context appropriate for multiple function calls
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*/
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oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
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fctx = (generate_subscripts_fctx *) palloc(sizeof(generate_subscripts_fctx));
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lb = ARR_LBOUND(v);
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dimv = ARR_DIMS(v);
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fctx->lower = lb[reqdim - 1];
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fctx->upper = dimv[reqdim - 1] + lb[reqdim - 1] - 1;
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fctx->reverse = (PG_NARGS() < 3) ? false : PG_GETARG_BOOL(2);
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funcctx->user_fctx = fctx;
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MemoryContextSwitchTo(oldcontext);
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}
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funcctx = SRF_PERCALL_SETUP();
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fctx = funcctx->user_fctx;
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if (fctx->lower <= fctx->upper)
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{
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if (!fctx->reverse)
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SRF_RETURN_NEXT(funcctx, Int32GetDatum(fctx->lower++));
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else
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SRF_RETURN_NEXT(funcctx, Int32GetDatum(fctx->upper--));
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}
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else
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/* done when there are no more elements left */
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SRF_RETURN_DONE(funcctx);
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}
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/*
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* generate_subscripts_nodir
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* Implements the 2-argument version of generate_subscripts
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*/
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Datum
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generate_subscripts_nodir(PG_FUNCTION_ARGS)
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{
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/* just call the other one -- it can handle both cases */
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return generate_subscripts(fcinfo);
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}
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.492 2008/04/17 20:56:41 momjian Exp $
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* $PostgreSQL: pgsql/src/include/catalog/pg_proc.h,v 1.493 2008/04/28 14:48:57 alvherre Exp $
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*
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* NOTES
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* The script catalog/genbki.sh reads this file and generates .bki
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@ -1010,6 +1010,11 @@ DATA(insert OID = 515 ( array_larger PGNSP PGUID 12 1 0 f f t f i 2 2277 "22
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DESCR("larger of two");
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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_ ));
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DESCR("smaller of two");
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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_ ));
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DESCR("array subscripts generator");
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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_ ));
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DESCR("array subscripts generator");
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DATA(insert OID = 760 ( smgrin PGNSP PGUID 12 1 0 f f t f s 1 210 "2275" _null_ _null_ _null_ smgrin - _null_ _null_ ));
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DESCR("I/O");
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@ -49,7 +49,7 @@
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/utils/array.h,v 1.66 2008/01/01 19:45:59 momjian Exp $
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* $PostgreSQL: pgsql/src/include/utils/array.h,v 1.67 2008/04/28 14:48:57 alvherre Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -200,6 +200,8 @@ extern Datum array_lower(PG_FUNCTION_ARGS);
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extern Datum array_upper(PG_FUNCTION_ARGS);
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extern Datum array_larger(PG_FUNCTION_ARGS);
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extern Datum array_smaller(PG_FUNCTION_ARGS);
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extern Datum generate_subscripts(PG_FUNCTION_ARGS);
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extern Datum generate_subscripts_nodir(PG_FUNCTION_ARGS);
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extern Datum array_ref(ArrayType *array, int nSubscripts, int *indx,
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int arraytyplen, int elmlen, bool elmbyval, char elmalign,
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@ -903,3 +903,33 @@ select c2[2].f2 from comptable;
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drop type _comptype;
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drop table comptable;
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drop type comptype;
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create or replace function unnest1(anyarray)
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returns setof anyelement as $$
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select $1[s] from generate_subscripts($1,1) g(s);
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$$ language sql immutable;
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create or replace function unnest2(anyarray)
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returns setof anyelement as $$
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select $1[s1][s2] from generate_subscripts($1,1) g1(s1),
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generate_subscripts($1,2) g2(s2);
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$$ language sql immutable;
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select * from unnest1(array[1,2,3]);
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unnest1
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---------
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1
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2
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3
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(3 rows)
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select * from unnest2(array[[1,2,3],[4,5,6]]);
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unnest2
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---------
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1
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2
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3
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4
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5
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6
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(6 rows)
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drop function unnest1(anyarray);
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drop function unnest2(anyarray);
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@ -340,3 +340,20 @@ select c2[2].f2 from comptable;
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drop type _comptype;
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drop table comptable;
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drop type comptype;
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create or replace function unnest1(anyarray)
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returns setof anyelement as $$
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select $1[s] from generate_subscripts($1,1) g(s);
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$$ language sql immutable;
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create or replace function unnest2(anyarray)
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returns setof anyelement as $$
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select $1[s1][s2] from generate_subscripts($1,1) g1(s1),
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generate_subscripts($1,2) g2(s2);
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$$ language sql immutable;
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select * from unnest1(array[1,2,3]);
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select * from unnest2(array[[1,2,3],[4,5,6]]);
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drop function unnest1(anyarray);
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drop function unnest2(anyarray);
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