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robertmhaasrobertmhaas
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Make new event trigger facility actually do something.
Commit 3855968 added syntax, pg_dump, psql support, and documentation, but the triggers didn't actually fire. With this commit, they now do. This is still a pretty basic facility overall because event triggers do not get a whole lot of information about what the user is trying to do unless you write them in C; and there's still no option to fire them anywhere except at the very beginning of the execution sequence, but it's better than nothing, and a good building block for future work. Along the way, add a regression test for ALTER LARGE OBJECT, since testing of event triggers reveals that we haven't got one. Dimitri Fontaine and Robert Haas
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‎contrib/pg_stat_statements/pg_stat_statements.c

Lines changed: 9 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -240,8 +240,9 @@ static void pgss_ExecutorRun(QueryDesc *queryDesc,
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static void pgss_ExecutorFinish(QueryDesc *queryDesc);
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static void pgss_ExecutorEnd(QueryDesc *queryDesc);
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static void pgss_ProcessUtility(Node *parsetree,
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const char *queryString, ParamListInfo params, bool isTopLevel,
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DestReceiver *dest, char *completionTag);
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const char *queryString, ParamListInfo params,
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DestReceiver *dest, char *completionTag,
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ProcessUtilityContext context);
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static uint32 pgss_hash_fn(const void *key, Size keysize);
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static int pgss_match_fn(const void *key1, const void *key2, Size keysize);
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static uint32 pgss_hash_string(const char *str);
@@ -785,8 +786,8 @@ pgss_ExecutorEnd(QueryDesc *queryDesc)
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*/
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static void
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pgss_ProcessUtility(Node *parsetree, const char *queryString,
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ParamListInfo params, bool isTopLevel,
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DestReceiver *dest, char *completionTag)
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ParamListInfo params, DestReceiver *dest,
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char *completionTag, ProcessUtilityContext context)
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{
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/*
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* If it's an EXECUTE statement, we don't track it and don't increment the
@@ -819,10 +820,10 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
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{
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if (prev_ProcessUtility)
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prev_ProcessUtility(parsetree, queryString, params,
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isTopLevel, dest, completionTag);
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dest, completionTag, context);
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else
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standard_ProcessUtility(parsetree, queryString, params,
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isTopLevel, dest, completionTag);
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dest, completionTag, context);
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nested_level--;
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}
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PG_CATCH();
@@ -880,10 +881,10 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
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{
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if (prev_ProcessUtility)
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prev_ProcessUtility(parsetree, queryString, params,
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isTopLevel, dest, completionTag);
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dest, completionTag, context);
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else
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standard_ProcessUtility(parsetree, queryString, params,
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isTopLevel, dest, completionTag);
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dest, completionTag, context);
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}
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}
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‎doc/src/sgml/plpgsql.sgml

Lines changed: 68 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3377,7 +3377,10 @@ RAISE unique_violation USING MESSAGE = 'Duplicate user ID: ' || user_id;
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<secondary>in PL/pgSQL</secondary>
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</indexterm>
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<para>
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<sect2 id="plpgsql-dml-trigger">
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<title>Triggers on data changes</title>
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<para>
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<application>PL/pgSQL</application> can be used to define trigger
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procedures. A trigger procedure is created with the
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<command>CREATE FUNCTION</> command, declaring it as a function with
@@ -3924,6 +3927,70 @@ UPDATE sales_fact SET units_sold = units_sold * 2;
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SELECT * FROM sales_summary_bytime;
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</programlisting>
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</example>
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</sect2>
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<sect2 id="plpgsql-event-trigger">
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<title>Triggers on events</title>
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<para>
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<application>PL/pgSQL</application> can be used to define event
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triggers. <productname>PostgreSQL</> requires that a procedure that
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is to be called as an event trigger must be declared as a function with
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no arguments and a return type of <literal>event_trigger</>.
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</para>
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<para>
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When a <application>PL/pgSQL</application> function is called as a
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event trigger, several special variables are created automatically
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in the top-level block. They are:
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<variablelist>
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<varlistentry>
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<term><varname>TG_EVENT</varname></term>
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<listitem>
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<para>
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Data type <type>text</type>; a string representing the event the
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trigger is fired for.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>TG_TAG</varname></term>
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<listitem>
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<para>
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Data type <type>text</type>; variable that contains the command tag
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for which the trigger is fired.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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<xref linkend="plpgsql-event-trigger-example"> shows an example of a
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event trigger procedure in <application>PL/pgSQL</application>.
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</para>
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<example id="plpgsql-event-trigger-example">
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<title>A <application>PL/pgSQL</application> Event Trigger Procedure</title>
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<para>
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This example trigger simply raises a <literal>NOTICE</literal> message
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each time a supported command is executed.
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</para>
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<programlisting>
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CREATE OR REPLACE FUNCTION snitch() RETURNS event_trigger AS $$
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BEGIN
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RAISE NOTICE 'snitch: % %', tg_event, tg_tag;
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END;
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$$ LANGUAGE plpgsql;
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3990+
CREATE EVENT TRIGGER snitch ON ddl_command_start EXECUTE PROCEDURE snitch();
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</programlisting>
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</example>
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</sect2>
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</sect1>
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‎doc/src/sgml/ref/create_event_trigger.sgml

Lines changed: 0 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -98,12 +98,6 @@ CREATE EVENT TRIGGER <replaceable class="PARAMETER">name</replaceable>
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A user-supplied function that is declared as taking no argument and
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returning type <literal>event_trigger</literal>.
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</para>
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<para>
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If your event trigger is implemented in <literal>C</literal> then it
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will be called with an argument, of
104-
type <literal>internal</literal>, which is a pointer to
105-
the <literal>Node *</literal> parse tree.
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</para>
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</listitem>
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</varlistentry>
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