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Follow-on cleanup for the transition table patch.
Commit 5970271 added transition table support to PL/pgsql so that SQL queries in trigger functions could access those transient tables. In order to provide the same level of support for PL/perl, PL/python and PL/tcl, refactor the relevant code into a new function SPI_register_trigger_data. Call the new function in the trigger handler of all four PLs, and document it as a public SPI function so that authors of out-of-tree PLs can do the same. Also get rid of a second QueryEnvironment object that was maintained by PL/pgsql. That was previously used to deal with cursors, but the same approach wasn't appropriate for PLs that are less tangled up with core code. Instead, have SPI_cursor_open install the connection's current QueryEnvironment, as already happens for SPI_execute_plan. While in the docs, remove the note that transition tables were only supported in C and PL/pgSQL triggers, and correct some ommissions. Thomas Munro with some work by Kevin Grittner (mostly docs)
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‎doc/src/sgml/ref/create_trigger.sgml

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,11 @@ PostgreSQL documentation
88
<primary>CREATE TRIGGER</primary>
99
</indexterm>
1010

11+
<indexterm>
12+
<primary>transition tables</primary>
13+
<seealso>ephemeral named relation</seealso>
14+
</indexterm>
15+
1116
<refmeta>
1217
<refentrytitle>CREATE TRIGGER</refentrytitle>
1318
<manvolnum>7</manvolnum>
@@ -322,11 +327,6 @@ UPDATE OF <replaceable>column_name1</replaceable> [, <replaceable>column_name2</
322327
<para>
323328
The (unqualified) name to be used within the trigger for this relation.
324329
</para>
325-
<note>
326-
<para>
327-
So far only triggers written in C or PL/pgSQL support this.
328-
</para>
329-
</note>
330330
</listitem>
331331
</varlistentry>
332332

‎doc/src/sgml/spi.sgml

Lines changed: 125 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2644,6 +2644,11 @@ SPIPlanPtr SPI_saveplan(SPIPlanPtr <parameter>plan</parameter>)
26442644
<refentry id="spi-spi-register-relation">
26452645
<indexterm><primary>SPI_register_relation</primary></indexterm>
26462646

2647+
<indexterm>
2648+
<primary>ephemeral named relation</primary>
2649+
<secondary>registering with SPI</secondary>
2650+
</indexterm>
2651+
26472652
<refmeta>
26482653
<refentrytitle>SPI_register_relation</refentrytitle>
26492654
<manvolnum>3</manvolnum>
@@ -2746,6 +2751,11 @@ int SPI_register_relation(EphemeralNamedRelation <parameter>enr</parameter>)
27462751
<refentry id="spi-spi-unregister-relation">
27472752
<indexterm><primary>SPI_unregister_relation</primary></indexterm>
27482753

2754+
<indexterm>
2755+
<primary>ephemeral named relation</primary>
2756+
<secondary>unregistering from SPI</secondary>
2757+
</indexterm>
2758+
27492759
<refmeta>
27502760
<refentrytitle>SPI_unregister_relation</refentrytitle>
27512761
<manvolnum>3</manvolnum>
@@ -2843,6 +2853,121 @@ int SPI_unregister_relation(const char * <parameter>name</parameter>)
28432853

28442854
<!-- *********************************************** -->
28452855

2856+
<refentry id="spi-spi-register-trigger-data">
2857+
<indexterm><primary>SPI_register_trigger_data</primary></indexterm>
2858+
2859+
<indexterm>
2860+
<primary>ephemeral named relation</primary>
2861+
<secondary>registering with SPI</secondary>
2862+
</indexterm>
2863+
2864+
<indexterm>
2865+
<primary>transition tables</primary>
2866+
<secondary>implementation in PLs</secondary>
2867+
</indexterm>
2868+
2869+
<refmeta>
2870+
<refentrytitle>SPI_register_trigger_data</refentrytitle>
2871+
<manvolnum>3</manvolnum>
2872+
</refmeta>
2873+
2874+
<refnamediv>
2875+
<refname>SPI_register_trigger_data</refname>
2876+
<refpurpose>make ephemeral trigger data available in SPI queries</refpurpose>
2877+
</refnamediv>
2878+
2879+
<refsynopsisdiv>
2880+
<synopsis>
2881+
int SPI_register_trigger_data(TriggerData *<parameter>tdata</parameter>)
2882+
</synopsis>
2883+
</refsynopsisdiv>
2884+
2885+
<refsect1>
2886+
<title>Description</title>
2887+
2888+
<para>
2889+
<function>SPI_register_trigger_data</function> makes any ephemeral
2890+
relations captured by a trigger available to queries planned and executed
2891+
through the current SPI connection. Currently, this means the transition
2892+
tables captured by an <literal>AFTER</literal> trigger defined with a
2893+
<literal>REFERENCING OLD/NEW TABLE AS</literal> ... clause. This function
2894+
should be called by a PL trigger handler function after connecting.
2895+
</para>
2896+
</refsect1>
2897+
2898+
<refsect1>
2899+
<title>Arguments</title>
2900+
2901+
<variablelist>
2902+
<varlistentry>
2903+
<term><literal>TriggerData *<parameter>tdata</parameter></literal></term>
2904+
<listitem>
2905+
<para>
2906+
the <structname>TriggerData</structname> object passed to a trigger
2907+
handler function as <literal>fcinfo->context</literal>
2908+
</para>
2909+
</listitem>
2910+
</varlistentry>
2911+
</variablelist>
2912+
</refsect1>
2913+
2914+
<refsect1>
2915+
<title>Return Value</title>
2916+
2917+
<para>
2918+
If the execution of the command was successful then the following
2919+
(nonnegative) value will be returned:
2920+
2921+
<variablelist>
2922+
<varlistentry>
2923+
<term><symbol>SPI_OK_TD_REGISTER</symbol></term>
2924+
<listitem>
2925+
<para>
2926+
if the captured trigger data (if any) has been successfully registered
2927+
</para>
2928+
</listitem>
2929+
</varlistentry>
2930+
</variablelist>
2931+
</para>
2932+
2933+
<para>
2934+
On error, one of the following negative values is returned:
2935+
2936+
<variablelist>
2937+
<varlistentry>
2938+
<term><symbol>SPI_ERROR_ARGUMENT</symbol></term>
2939+
<listitem>
2940+
<para>
2941+
if <parameter>tdata</parameter> is <symbol>NULL</symbol>
2942+
</para>
2943+
</listitem>
2944+
</varlistentry>
2945+
2946+
<varlistentry>
2947+
<term><symbol>SPI_ERROR_UNCONNECTED</symbol></term>
2948+
<listitem>
2949+
<para>
2950+
if called from an unconnected procedure
2951+
</para>
2952+
</listitem>
2953+
</varlistentry>
2954+
2955+
<varlistentry>
2956+
<term><symbol>SPI_ERROR_REL_DUPLICATE</symbol></term>
2957+
<listitem>
2958+
<para>
2959+
if the name of any trigger data transient relation is already
2960+
registered for this connection
2961+
</para>
2962+
</listitem>
2963+
</varlistentry>
2964+
</variablelist>
2965+
</para>
2966+
</refsect1>
2967+
</refentry>
2968+
2969+
<!-- *********************************************** -->
2970+
28462971
</sect1>
28472972

28482973
<sect1 id="spi-interface-support">

‎doc/src/sgml/trigger.sgml

Lines changed: 46 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -395,6 +395,11 @@
395395
<secondary>in C</secondary>
396396
</indexterm>
397397

398+
<indexterm>
399+
<primary>transition tables</primary>
400+
<secondary>referencing from C trigger</secondary>
401+
</indexterm>
402+
398403
<para>
399404
This section describes the low-level details of the interface to a
400405
trigger function. This information is only needed when writing
@@ -438,14 +443,16 @@ CALLED_AS_TRIGGER(fcinfo)
438443
<programlisting>
439444
typedef struct TriggerData
440445
{
441-
NodeTag type;
442-
TriggerEvent tg_event;
443-
Relation tg_relation;
444-
HeapTuple tg_trigtuple;
445-
HeapTuple tg_newtuple;
446-
Trigger *tg_trigger;
447-
Buffer tg_trigtuplebuf;
448-
Buffer tg_newtuplebuf;
446+
NodeTag type;
447+
TriggerEvent tg_event;
448+
Relation tg_relation;
449+
HeapTuple tg_trigtuple;
450+
HeapTuple tg_newtuple;
451+
Trigger *tg_trigger;
452+
Buffer tg_trigtuplebuf;
453+
Buffer tg_newtuplebuf;
454+
Tuplestorestate *tg_oldtable;
455+
Tuplestorestate *tg_newtable;
449456
} TriggerData;
450457
</programlisting>
451458

@@ -629,6 +636,8 @@ typedef struct Trigger
629636
int16 *tgattr;
630637
char **tgargs;
631638
char *tgqual;
639+
char *tgoldtable;
640+
char *tgnewtable;
632641
} Trigger;
633642
</programlisting>
634643

@@ -662,9 +671,38 @@ typedef struct Trigger
662671
</listitem>
663672
</varlistentry>
664673

674+
<varlistentry>
675+
<term><structfield>tg_oldtable</></term>
676+
<listitem>
677+
<para>
678+
A pointer to a structure of type <structname>Tuplestorestate</structname>
679+
containing zero or more rows in the format specified by
680+
<structfield>tg_relation</structfield>, or a <symbol>NULL</> pointer
681+
if there is no <literal>OLD TABLE</literal> transition relation.
682+
</para>
683+
</listitem>
684+
</varlistentry>
685+
686+
<varlistentry>
687+
<term><structfield>tg_newtable</></term>
688+
<listitem>
689+
<para>
690+
A pointer to a structure of type <structname>Tuplestorestate</structname>
691+
containing zero or more rows in the format specified by
692+
<structfield>tg_relation</structfield>, or a <symbol>NULL</> pointer
693+
if there is no <literal>NEW TABLE</literal> transition relation.
694+
</para>
695+
</listitem>
696+
</varlistentry>
697+
665698
</variablelist>
666699
</para>
667700

701+
<para>
702+
To allow queries issued through SPI to reference transition tables, see
703+
<xref linkend="spi-spi-register-trigger-data">.
704+
</para>
705+
668706
<para>
669707
A trigger function must return either a
670708
<structname>HeapTuple</> pointer or a <symbol>NULL</> pointer

‎src/backend/executor/spi.c

Lines changed: 52 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1257,6 +1257,9 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
12571257
errdetail("Scrollable cursors must be READ ONLY.")));
12581258
}
12591259

1260+
/* Make current query environment available to portal at execution time. */
1261+
portal->queryEnv = _SPI_current->queryEnv;
1262+
12601263
/*
12611264
* If told to be read-only, or in parallel mode, verify that this query is
12621265
* in fact read-only. This can't be done earlier because we need to look
@@ -2716,3 +2719,52 @@ SPI_unregister_relation(const char *name)
27162719

27172720
return res;
27182721
}
2722+
2723+
/*
2724+
* Register the transient relations from 'tdata' using this SPI connection.
2725+
* This should be called by PL implementations' trigger handlers after
2726+
* connecting, in order to make transition tables visible to any queries run
2727+
* in this connection.
2728+
*/
2729+
int
2730+
SPI_register_trigger_data(TriggerData *tdata)
2731+
{
2732+
if (tdata == NULL)
2733+
return SPI_ERROR_ARGUMENT;
2734+
2735+
if (tdata->tg_newtable)
2736+
{
2737+
EphemeralNamedRelation enr =
2738+
palloc(sizeof(EphemeralNamedRelationData));
2739+
int rc;
2740+
2741+
enr->md.name = tdata->tg_trigger->tgnewtable;
2742+
enr->md.reliddesc = tdata->tg_relation->rd_id;
2743+
enr->md.tupdesc = NULL;
2744+
enr->md.enrtype = ENR_NAMED_TUPLESTORE;
2745+
enr->md.enrtuples = tuplestore_tuple_count(tdata->tg_newtable);
2746+
enr->reldata = tdata->tg_newtable;
2747+
rc = SPI_register_relation(enr);
2748+
if (rc != SPI_OK_REL_REGISTER)
2749+
return rc;
2750+
}
2751+
2752+
if (tdata->tg_oldtable)
2753+
{
2754+
EphemeralNamedRelation enr =
2755+
palloc(sizeof(EphemeralNamedRelationData));
2756+
int rc;
2757+
2758+
enr->md.name = tdata->tg_trigger->tgoldtable;
2759+
enr->md.reliddesc = tdata->tg_relation->rd_id;
2760+
enr->md.tupdesc = NULL;
2761+
enr->md.enrtype = ENR_NAMED_TUPLESTORE;
2762+
enr->md.enrtuples = tuplestore_tuple_count(tdata->tg_oldtable);
2763+
enr->reldata = tdata->tg_oldtable;
2764+
rc = SPI_register_relation(enr);
2765+
if (rc != SPI_OK_REL_REGISTER)
2766+
return rc;
2767+
}
2768+
2769+
return SPI_OK_TD_REGISTER;
2770+
}

‎src/include/executor/spi.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -13,6 +13,7 @@
1313
#ifndef SPI_H
1414
#define SPI_H
1515

16+
#include "commands/trigger.h"
1617
#include "lib/ilist.h"
1718
#include "nodes/parsenodes.h"
1819
#include "utils/portal.h"
@@ -62,6 +63,7 @@ typedef struct _SPI_plan *SPIPlanPtr;
6263
#define SPI_OK_REWRITTEN 14
6364
#define SPI_OK_REL_REGISTER 15
6465
#define SPI_OK_REL_UNREGISTER 16
66+
#define SPI_OK_TD_REGISTER 17
6567

6668
/* These used to be functions, now just no-ops for backwards compatibility */
6769
#define SPI_push() ((void) 0)
@@ -152,6 +154,7 @@ extern void SPI_cursor_close(Portal portal);
152154

153155
extern int SPI_register_relation(EphemeralNamedRelation enr);
154156
extern int SPI_unregister_relation(const char *name);
157+
extern int SPI_register_trigger_data(TriggerData *tdata);
155158

156159
extern void AtEOXact_SPI(bool isCommit);
157160
extern void AtEOSubXact_SPI(bool isCommit, SubTransactionId mySubid);

‎src/pl/plperl/expected/plperl_trigger.out

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -241,6 +241,35 @@ $$ LANGUAGE plperl;
241241
SELECT direct_trigger();
242242
ERROR: trigger functions can only be called as triggers
243243
CONTEXT: compilation of PL/Perl function "direct_trigger"
244+
-- check that SQL run in trigger code can see transition tables
245+
CREATE TABLE transition_table_test (id int, name text);
246+
INSERT INTO transition_table_test VALUES (1, 'a');
247+
CREATE FUNCTION transition_table_test_f() RETURNS trigger LANGUAGE plperl AS
248+
$$
249+
my $cursor = spi_query("SELECT * FROM old_table");
250+
my $row = spi_fetchrow($cursor);
251+
defined($row) || die "expected a row";
252+
elog(INFO, "old: " . $row->{id} . " -> " . $row->{name});
253+
my $row = spi_fetchrow($cursor);
254+
!defined($row) || die "expected no more rows";
255+
256+
my $cursor = spi_query("SELECT * FROM new_table");
257+
my $row = spi_fetchrow($cursor);
258+
defined($row) || die "expected a row";
259+
elog(INFO, "new: " . $row->{id} . " -> " . $row->{name});
260+
my $row = spi_fetchrow($cursor);
261+
!defined($row) || die "expected no more rows";
262+
263+
return undef;
264+
$$;
265+
CREATE TRIGGER a_t AFTER UPDATE ON transition_table_test
266+
REFERENCING OLD TABLE AS old_table NEW TABLE AS new_table
267+
FOR EACH STATEMENT EXECUTE PROCEDURE transition_table_test_f();
268+
UPDATE transition_table_test SET name = 'b';
269+
INFO: old: 1 -> a
270+
INFO: new: 1 -> b
271+
DROP TABLE transition_table_test;
272+
DROP FUNCTION transition_table_test_f();
244273
-- test plperl command triggers
245274
create or replace function perlsnitch() returns event_trigger language plperl as $$
246275
elog(NOTICE, "perlsnitch: " . $_TD->{event} . " " . $_TD->{tag} . " ");

‎src/pl/plperl/plperl.c

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2442,11 +2442,18 @@ plperl_trigger_handler(PG_FUNCTION_ARGS)
24422442
SV *svTD;
24432443
HV *hvTD;
24442444
ErrorContextCallback pl_error_context;
2445+
TriggerData *tdata;
2446+
int rc PG_USED_FOR_ASSERTS_ONLY;
24452447

24462448
/* Connect to SPI manager */
24472449
if (SPI_connect() != SPI_OK_CONNECT)
24482450
elog(ERROR, "could not connect to SPI manager");
24492451

2452+
/* Make transition tables visible to this SPI connection */
2453+
tdata = (TriggerData *) fcinfo->context;
2454+
rc = SPI_register_trigger_data(tdata);
2455+
Assert(rc >= 0);
2456+
24502457
/* Find or compile the function */
24512458
prodesc = compile_plperl_function(fcinfo->flinfo->fn_oid, true, false);
24522459
current_call_data->prodesc = prodesc;

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