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Follow-on cleanup for the transition table patch.

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Commit 59702716 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)
This commit is contained in:
Kevin Grittner
2017-04-04 18:36:39 -05:00
parent 9a3215026b
commit 5ebeb579b9
16 changed files with 398 additions and 63 deletions
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54
doc/src/sgml/trigger.sgml
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@@ -395,6 +395,11 @@
<secondary>in C</secondary>
</indexterm>
<indexterm>
<primary>transition tables</primary>
<secondary>referencing from C trigger</secondary>
</indexterm>
<para>
This section describes the low-level details of the interface to a
trigger function. This information is only needed when writing
@@ -438,14 +443,16 @@ CALLED_AS_TRIGGER(fcinfo)
<programlisting>
typedef struct TriggerData
{
NodeTag type;
TriggerEvent tg_event;
Relation tg_relation;
HeapTuple tg_trigtuple;
HeapTuple tg_newtuple;
Trigger *tg_trigger;
Buffer tg_trigtuplebuf;
Buffer tg_newtuplebuf;
NodeTag type;
TriggerEvent tg_event;
Relation tg_relation;
HeapTuple tg_trigtuple;
HeapTuple tg_newtuple;
Trigger *tg_trigger;
Buffer tg_trigtuplebuf;
Buffer tg_newtuplebuf;
Tuplestorestate *tg_oldtable;
Tuplestorestate *tg_newtable;
} TriggerData;
</programlisting>
@@ -629,6 +636,8 @@ typedef struct Trigger
int16 *tgattr;
char **tgargs;
char *tgqual;
char *tgoldtable;
char *tgnewtable;
} Trigger;
</programlisting>
@@ -662,9 +671,38 @@ typedef struct Trigger
</listitem>
</varlistentry>
<varlistentry>
<term><structfield>tg_oldtable</></term>
<listitem>
<para>
A pointer to a structure of type <structname>Tuplestorestate</structname>
containing zero or more rows in the format specified by
<structfield>tg_relation</structfield>, or a <symbol>NULL</> pointer
if there is no <literal>OLD TABLE</literal> transition relation.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><structfield>tg_newtable</></term>
<listitem>
<para>
A pointer to a structure of type <structname>Tuplestorestate</structname>
containing zero or more rows in the format specified by
<structfield>tg_relation</structfield>, or a <symbol>NULL</> pointer
if there is no <literal>NEW TABLE</literal> transition relation.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
To allow queries issued through SPI to reference transition tables, see
<xref linkend="spi-spi-register-trigger-data">.
</para>
<para>
A trigger function must return either a
<structname>HeapTuple</> pointer or a <symbol>NULL</> pointer