Extend plsample example to include a trigger handler.
Mark Wong and Konstantina Skovola, reviewed by Chapman Flack Discussion: https://postgr.es/m/Yd8Cz22eHi80XS30@workstation-mark-wong
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Tom Lane
parent
9f8a050f68
commit
2f4d0d6799
@ -34,3 +34,84 @@ NOTICE: argument: 0; name: a1; value: {foo,bar,hoge}
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(1 row)
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CREATE FUNCTION my_trigger_func() RETURNS trigger AS $$
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if TD_event == "INSERT"
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return TD_NEW
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elseif TD_event == "UPDATE"
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return TD_NEW
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else
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return "OK"
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end
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$$ language plsample;
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CREATE TABLE my_table (num integer, description text);
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CREATE TRIGGER my_trigger_func BEFORE INSERT OR UPDATE ON my_table
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FOR EACH ROW EXECUTE FUNCTION my_trigger_func();
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CREATE TRIGGER my_trigger_func2 AFTER INSERT OR UPDATE ON my_table
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FOR EACH ROW EXECUTE FUNCTION my_trigger_func(8);
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INSERT INTO my_table (num, description)
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VALUES (1, 'first');
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NOTICE: source text of function "my_trigger_func":
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if TD_event == "INSERT"
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return TD_NEW
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elseif TD_event == "UPDATE"
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return TD_NEW
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else
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return "OK"
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end
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NOTICE: trigger name: my_trigger_func
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NOTICE: trigger relation: my_table
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NOTICE: trigger relation schema: public
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NOTICE: triggered by INSERT
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NOTICE: triggered BEFORE
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NOTICE: triggered per row
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NOTICE: source text of function "my_trigger_func":
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if TD_event == "INSERT"
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return TD_NEW
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elseif TD_event == "UPDATE"
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return TD_NEW
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else
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return "OK"
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end
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NOTICE: trigger name: my_trigger_func2
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NOTICE: trigger relation: my_table
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NOTICE: trigger relation schema: public
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NOTICE: triggered by INSERT
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NOTICE: triggered AFTER
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NOTICE: triggered per row
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NOTICE: trigger arg[0]: 8
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UPDATE my_table
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SET description = 'first, modified once'
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WHERE num = 1;
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NOTICE: source text of function "my_trigger_func":
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if TD_event == "INSERT"
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return TD_NEW
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elseif TD_event == "UPDATE"
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return TD_NEW
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else
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return "OK"
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end
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NOTICE: trigger name: my_trigger_func
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NOTICE: trigger relation: my_table
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NOTICE: trigger relation schema: public
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NOTICE: triggered by UPDATE
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NOTICE: triggered BEFORE
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NOTICE: triggered per row
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NOTICE: source text of function "my_trigger_func":
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if TD_event == "INSERT"
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return TD_NEW
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elseif TD_event == "UPDATE"
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return TD_NEW
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else
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return "OK"
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end
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NOTICE: trigger name: my_trigger_func2
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NOTICE: trigger relation: my_table
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NOTICE: trigger relation schema: public
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NOTICE: triggered by UPDATE
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NOTICE: triggered AFTER
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NOTICE: triggered per row
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NOTICE: trigger arg[0]: 8
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@ -19,6 +19,7 @@
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#include "catalog/pg_type.h"
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#include "commands/event_trigger.h"
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#include "commands/trigger.h"
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#include "executor/spi.h"
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#include "funcapi.h"
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#include "utils/builtins.h"
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#include "utils/lsyscache.h"
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@ -29,6 +30,7 @@ PG_MODULE_MAGIC;
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PG_FUNCTION_INFO_V1(plsample_call_handler);
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static Datum plsample_func_handler(PG_FUNCTION_ARGS);
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static HeapTuple plsample_trigger_handler(PG_FUNCTION_ARGS);
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/*
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* Handle function, procedure, and trigger calls.
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@ -38,6 +40,11 @@ plsample_call_handler(PG_FUNCTION_ARGS)
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{
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Datum retval = (Datum) 0;
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/*
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* Many languages will require cleanup that happens even in the event of
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* an error. That can happen in the PG_FINALLY block. If none is needed,
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* this PG_TRY construct can be omitted.
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*/
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PG_TRY();
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{
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/*
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@ -51,6 +58,7 @@ plsample_call_handler(PG_FUNCTION_ARGS)
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* (TriggerData *) fcinfo->context includes the information of the
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* context.
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*/
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retval = PointerGetDatum(plsample_trigger_handler(fcinfo));
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}
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else if (CALLED_AS_EVENT_TRIGGER(fcinfo))
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{
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@ -58,6 +66,8 @@ plsample_call_handler(PG_FUNCTION_ARGS)
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* This function is called as an event trigger function, where
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* (EventTriggerData *) fcinfo->context includes the information
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* of the context.
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*
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* TODO: provide an example handler.
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*/
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}
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else
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@ -101,9 +111,9 @@ plsample_func_handler(PG_FUNCTION_ARGS)
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FmgrInfo result_in_func;
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int numargs;
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/* Fetch the source text of the function. */
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pl_tuple = SearchSysCache(PROCOID,
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ObjectIdGetDatum(fcinfo->flinfo->fn_oid), 0, 0, 0);
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/* Fetch the function's pg_proc entry. */
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pl_tuple = SearchSysCache1(PROCOID,
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ObjectIdGetDatum(fcinfo->flinfo->fn_oid));
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if (!HeapTupleIsValid(pl_tuple))
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elog(ERROR, "cache lookup failed for function %u",
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fcinfo->flinfo->fn_oid);
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@ -185,3 +195,160 @@ plsample_func_handler(PG_FUNCTION_ARGS)
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ret = InputFunctionCall(&result_in_func, source, result_typioparam, -1);
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PG_RETURN_DATUM(ret);
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}
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/*
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* plsample_trigger_handler
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*
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* Function called by the call handler for trigger execution.
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*/
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static HeapTuple
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plsample_trigger_handler(PG_FUNCTION_ARGS)
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{
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TriggerData *trigdata = (TriggerData *) fcinfo->context;
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char *string;
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volatile HeapTuple rettup;
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HeapTuple pl_tuple;
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Datum ret;
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char *source;
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bool isnull;
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Form_pg_proc pl_struct;
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char *proname;
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int rc PG_USED_FOR_ASSERTS_ONLY;
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/* Make sure this is being called from a trigger. */
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if (!CALLED_AS_TRIGGER(fcinfo))
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elog(ERROR, "not called by trigger manager");
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/* Connect to the SPI manager */
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if (SPI_connect() != SPI_OK_CONNECT)
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elog(ERROR, "could not connect to SPI manager");
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rc = SPI_register_trigger_data(trigdata);
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Assert(rc >= 0);
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/* Fetch the function's pg_proc entry. */
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pl_tuple = SearchSysCache1(PROCOID,
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ObjectIdGetDatum(fcinfo->flinfo->fn_oid));
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if (!HeapTupleIsValid(pl_tuple))
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elog(ERROR, "cache lookup failed for function %u",
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fcinfo->flinfo->fn_oid);
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/*
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* Code Retrieval
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*
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* Extract and print the source text of the function. This can be used as
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* a base for the function validation and execution.
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*/
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pl_struct = (Form_pg_proc) GETSTRUCT(pl_tuple);
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proname = pstrdup(NameStr(pl_struct->proname));
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ret = SysCacheGetAttr(PROCOID, pl_tuple, Anum_pg_proc_prosrc, &isnull);
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if (isnull)
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elog(ERROR, "could not find source text of function \"%s\"",
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proname);
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source = DatumGetCString(DirectFunctionCall1(textout, ret));
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ereport(NOTICE,
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(errmsg("source text of function \"%s\": %s",
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proname, source)));
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/*
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* We're done with the pg_proc tuple, so release it. (Note that the
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* "proname" and "source" strings are now standalone copies.)
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*/
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ReleaseSysCache(pl_tuple);
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/*
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* Code Augmentation
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*
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* The source text may be augmented here, such as by wrapping it as the
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* body of a function in the target language, prefixing a parameter list
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* with names like TD_name, TD_relid, TD_table_name, TD_table_schema,
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* TD_event, TD_when, TD_level, TD_NEW, TD_OLD, and args, using whatever
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* types in the target language are convenient. The augmented text can be
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* cached in a longer-lived memory context, or, if the target language
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* uses a compilation step, that can be done here, caching the result of
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* the compilation.
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*/
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/*
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* Code Execution
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*
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* Here the function (the possibly-augmented source text, or the result of
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* compilation if the target language uses such a step) should be
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* executed, after binding values from the TriggerData struct to the
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* appropriate parameters.
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*
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* In this example we just print a lot of info via ereport.
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*/
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PG_TRY();
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{
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ereport(NOTICE,
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(errmsg("trigger name: %s", trigdata->tg_trigger->tgname)));
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string = SPI_getrelname(trigdata->tg_relation);
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ereport(NOTICE, (errmsg("trigger relation: %s", string)));
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string = SPI_getnspname(trigdata->tg_relation);
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ereport(NOTICE, (errmsg("trigger relation schema: %s", string)));
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/* Example handling of different trigger aspects. */
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if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
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{
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ereport(NOTICE, (errmsg("triggered by INSERT")));
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rettup = trigdata->tg_trigtuple;
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}
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else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
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{
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ereport(NOTICE, (errmsg("triggered by DELETE")));
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rettup = trigdata->tg_trigtuple;
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}
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else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
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{
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ereport(NOTICE, (errmsg("triggered by UPDATE")));
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rettup = trigdata->tg_trigtuple;
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}
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else if (TRIGGER_FIRED_BY_TRUNCATE(trigdata->tg_event))
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{
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ereport(NOTICE, (errmsg("triggered by TRUNCATE")));
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rettup = trigdata->tg_trigtuple;
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}
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else
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elog(ERROR, "unrecognized event: %u", trigdata->tg_event);
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if (TRIGGER_FIRED_BEFORE(trigdata->tg_event))
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ereport(NOTICE, (errmsg("triggered BEFORE")));
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else if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
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ereport(NOTICE, (errmsg("triggered AFTER")));
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else if (TRIGGER_FIRED_INSTEAD(trigdata->tg_event))
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ereport(NOTICE, (errmsg("triggered INSTEAD OF")));
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else
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elog(ERROR, "unrecognized when: %u", trigdata->tg_event);
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if (TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
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ereport(NOTICE, (errmsg("triggered per row")));
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else if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
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ereport(NOTICE, (errmsg("triggered per statement")));
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else
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elog(ERROR, "unrecognized level: %u", trigdata->tg_event);
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/*
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* Iterate through all of the trigger arguments, printing each input
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* value.
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*/
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for (int i = 0; i < trigdata->tg_trigger->tgnargs; i++)
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ereport(NOTICE,
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(errmsg("trigger arg[%i]: %s", i,
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trigdata->tg_trigger->tgargs[i])));
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}
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PG_CATCH();
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{
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/* Error cleanup code would go here */
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PG_RE_THROW();
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}
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PG_END_TRY();
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if (SPI_finish() != SPI_OK_FINISH)
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elog(ERROR, "SPI_finish() failed");
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return rettup;
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}
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@ -13,3 +13,26 @@ AS $$
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Example of source with void result.
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$$ LANGUAGE plsample;
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SELECT plsample_result_void('{foo, bar, hoge}');
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CREATE FUNCTION my_trigger_func() RETURNS trigger AS $$
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if TD_event == "INSERT"
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return TD_NEW
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elseif TD_event == "UPDATE"
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return TD_NEW
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else
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return "OK"
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end
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$$ language plsample;
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CREATE TABLE my_table (num integer, description text);
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CREATE TRIGGER my_trigger_func BEFORE INSERT OR UPDATE ON my_table
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FOR EACH ROW EXECUTE FUNCTION my_trigger_func();
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CREATE TRIGGER my_trigger_func2 AFTER INSERT OR UPDATE ON my_table
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FOR EACH ROW EXECUTE FUNCTION my_trigger_func(8);
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INSERT INTO my_table (num, description)
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VALUES (1, 'first');
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UPDATE my_table
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SET description = 'first, modified once'
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WHERE num = 1;
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