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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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‎src/test/modules/plsample/expected/plsample.out

Lines changed: 81 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -34,3 +34,84 @@ NOTICE: argument: 0; name: a1; value: {foo,bar,hoge}
3434

3535
(1 row)
3636

37+
CREATE FUNCTION my_trigger_func() RETURNS trigger AS $$
38+
if TD_event == "INSERT"
39+
return TD_NEW
40+
elseif TD_event == "UPDATE"
41+
return TD_NEW
42+
else
43+
return "OK"
44+
end
45+
$$ language plsample;
46+
CREATE TABLE my_table (num integer, description text);
47+
CREATE TRIGGER my_trigger_func BEFORE INSERT OR UPDATE ON my_table
48+
FOR EACH ROW EXECUTE FUNCTION my_trigger_func();
49+
CREATE TRIGGER my_trigger_func2 AFTER INSERT OR UPDATE ON my_table
50+
FOR EACH ROW EXECUTE FUNCTION my_trigger_func(8);
51+
INSERT INTO my_table (num, description)
52+
VALUES (1, 'first');
53+
NOTICE: source text of function "my_trigger_func":
54+
if TD_event == "INSERT"
55+
return TD_NEW
56+
elseif TD_event == "UPDATE"
57+
return TD_NEW
58+
else
59+
return "OK"
60+
end
61+
62+
NOTICE: trigger name: my_trigger_func
63+
NOTICE: trigger relation: my_table
64+
NOTICE: trigger relation schema: public
65+
NOTICE: triggered by INSERT
66+
NOTICE: triggered BEFORE
67+
NOTICE: triggered per row
68+
NOTICE: source text of function "my_trigger_func":
69+
if TD_event == "INSERT"
70+
return TD_NEW
71+
elseif TD_event == "UPDATE"
72+
return TD_NEW
73+
else
74+
return "OK"
75+
end
76+
77+
NOTICE: trigger name: my_trigger_func2
78+
NOTICE: trigger relation: my_table
79+
NOTICE: trigger relation schema: public
80+
NOTICE: triggered by INSERT
81+
NOTICE: triggered AFTER
82+
NOTICE: triggered per row
83+
NOTICE: trigger arg[0]: 8
84+
UPDATE my_table
85+
SET description = 'first, modified once'
86+
WHERE num = 1;
87+
NOTICE: source text of function "my_trigger_func":
88+
if TD_event == "INSERT"
89+
return TD_NEW
90+
elseif TD_event == "UPDATE"
91+
return TD_NEW
92+
else
93+
return "OK"
94+
end
95+
96+
NOTICE: trigger name: my_trigger_func
97+
NOTICE: trigger relation: my_table
98+
NOTICE: trigger relation schema: public
99+
NOTICE: triggered by UPDATE
100+
NOTICE: triggered BEFORE
101+
NOTICE: triggered per row
102+
NOTICE: source text of function "my_trigger_func":
103+
if TD_event == "INSERT"
104+
return TD_NEW
105+
elseif TD_event == "UPDATE"
106+
return TD_NEW
107+
else
108+
return "OK"
109+
end
110+
111+
NOTICE: trigger name: my_trigger_func2
112+
NOTICE: trigger relation: my_table
113+
NOTICE: trigger relation schema: public
114+
NOTICE: triggered by UPDATE
115+
NOTICE: triggered AFTER
116+
NOTICE: triggered per row
117+
NOTICE: trigger arg[0]: 8

‎src/test/modules/plsample/plsample.c

Lines changed: 170 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -19,6 +19,7 @@
1919
#include "catalog/pg_type.h"
2020
#include "commands/event_trigger.h"
2121
#include "commands/trigger.h"
22+
#include "executor/spi.h"
2223
#include "funcapi.h"
2324
#include "utils/builtins.h"
2425
#include "utils/lsyscache.h"
@@ -29,6 +30,7 @@ PG_MODULE_MAGIC;
2930
PG_FUNCTION_INFO_V1(plsample_call_handler);
3031

3132
static Datum plsample_func_handler(PG_FUNCTION_ARGS);
33+
static HeapTuple plsample_trigger_handler(PG_FUNCTION_ARGS);
3234

3335
/*
3436
* Handle function, procedure, and trigger calls.
@@ -38,6 +40,11 @@ plsample_call_handler(PG_FUNCTION_ARGS)
3840
{
3941
Datum retval = (Datum) 0;
4042

43+
/*
44+
* Many languages will require cleanup that happens even in the event of
45+
* an error. That can happen in the PG_FINALLY block. If none is needed,
46+
* this PG_TRY construct can be omitted.
47+
*/
4148
PG_TRY();
4249
{
4350
/*
@@ -51,13 +58,16 @@ plsample_call_handler(PG_FUNCTION_ARGS)
5158
* (TriggerData *) fcinfo->context includes the information of the
5259
* context.
5360
*/
61+
retval = PointerGetDatum(plsample_trigger_handler(fcinfo));
5462
}
5563
else if (CALLED_AS_EVENT_TRIGGER(fcinfo))
5664
{
5765
/*
5866
* This function is called as an event trigger function, where
5967
* (EventTriggerData *) fcinfo->context includes the information
6068
* of the context.
69+
*
70+
* TODO: provide an example handler.
6171
*/
6272
}
6373
else
@@ -101,9 +111,9 @@ plsample_func_handler(PG_FUNCTION_ARGS)
101111
FmgrInfo result_in_func;
102112
int numargs;
103113

104-
/* Fetch the source text of the function. */
105-
pl_tuple = SearchSysCache(PROCOID,
106-
ObjectIdGetDatum(fcinfo->flinfo->fn_oid), 0, 0, 0);
114+
/* Fetch the function's pg_proc entry. */
115+
pl_tuple = SearchSysCache1(PROCOID,
116+
ObjectIdGetDatum(fcinfo->flinfo->fn_oid));
107117
if (!HeapTupleIsValid(pl_tuple))
108118
elog(ERROR, "cache lookup failed for function %u",
109119
fcinfo->flinfo->fn_oid);
@@ -185,3 +195,160 @@ plsample_func_handler(PG_FUNCTION_ARGS)
185195
ret = InputFunctionCall(&result_in_func, source, result_typioparam, -1);
186196
PG_RETURN_DATUM(ret);
187197
}
198+
199+
/*
200+
* plsample_trigger_handler
201+
*
202+
* Function called by the call handler for trigger execution.
203+
*/
204+
static HeapTuple
205+
plsample_trigger_handler(PG_FUNCTION_ARGS)
206+
{
207+
TriggerData *trigdata = (TriggerData *) fcinfo->context;
208+
char *string;
209+
volatile HeapTuple rettup;
210+
HeapTuple pl_tuple;
211+
Datum ret;
212+
char *source;
213+
bool isnull;
214+
Form_pg_proc pl_struct;
215+
char *proname;
216+
int rc PG_USED_FOR_ASSERTS_ONLY;
217+
218+
/* Make sure this is being called from a trigger. */
219+
if (!CALLED_AS_TRIGGER(fcinfo))
220+
elog(ERROR, "not called by trigger manager");
221+
222+
/* Connect to the SPI manager */
223+
if (SPI_connect() != SPI_OK_CONNECT)
224+
elog(ERROR, "could not connect to SPI manager");
225+
226+
rc = SPI_register_trigger_data(trigdata);
227+
Assert(rc >= 0);
228+
229+
/* Fetch the function's pg_proc entry. */
230+
pl_tuple = SearchSysCache1(PROCOID,
231+
ObjectIdGetDatum(fcinfo->flinfo->fn_oid));
232+
if (!HeapTupleIsValid(pl_tuple))
233+
elog(ERROR, "cache lookup failed for function %u",
234+
fcinfo->flinfo->fn_oid);
235+
236+
/*
237+
* Code Retrieval
238+
*
239+
* Extract and print the source text of the function. This can be used as
240+
* a base for the function validation and execution.
241+
*/
242+
pl_struct = (Form_pg_proc) GETSTRUCT(pl_tuple);
243+
proname = pstrdup(NameStr(pl_struct->proname));
244+
ret = SysCacheGetAttr(PROCOID, pl_tuple, Anum_pg_proc_prosrc, &isnull);
245+
if (isnull)
246+
elog(ERROR, "could not find source text of function \"%s\"",
247+
proname);
248+
source = DatumGetCString(DirectFunctionCall1(textout, ret));
249+
ereport(NOTICE,
250+
(errmsg("source text of function \"%s\": %s",
251+
proname, source)));
252+
253+
/*
254+
* We're done with the pg_proc tuple, so release it. (Note that the
255+
* "proname" and "source" strings are now standalone copies.)
256+
*/
257+
ReleaseSysCache(pl_tuple);
258+
259+
/*
260+
* Code Augmentation
261+
*
262+
* The source text may be augmented here, such as by wrapping it as the
263+
* body of a function in the target language, prefixing a parameter list
264+
* with names like TD_name, TD_relid, TD_table_name, TD_table_schema,
265+
* TD_event, TD_when, TD_level, TD_NEW, TD_OLD, and args, using whatever
266+
* types in the target language are convenient. The augmented text can be
267+
* cached in a longer-lived memory context, or, if the target language
268+
* uses a compilation step, that can be done here, caching the result of
269+
* the compilation.
270+
*/
271+
272+
/*
273+
* Code Execution
274+
*
275+
* Here the function (the possibly-augmented source text, or the result of
276+
* compilation if the target language uses such a step) should be
277+
* executed, after binding values from the TriggerData struct to the
278+
* appropriate parameters.
279+
*
280+
* In this example we just print a lot of info via ereport.
281+
*/
282+
283+
PG_TRY();
284+
{
285+
ereport(NOTICE,
286+
(errmsg("trigger name: %s", trigdata->tg_trigger->tgname)));
287+
string = SPI_getrelname(trigdata->tg_relation);
288+
ereport(NOTICE, (errmsg("trigger relation: %s", string)));
289+
290+
string = SPI_getnspname(trigdata->tg_relation);
291+
ereport(NOTICE, (errmsg("trigger relation schema: %s", string)));
292+
293+
/* Example handling of different trigger aspects. */
294+
295+
if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
296+
{
297+
ereport(NOTICE, (errmsg("triggered by INSERT")));
298+
rettup = trigdata->tg_trigtuple;
299+
}
300+
else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
301+
{
302+
ereport(NOTICE, (errmsg("triggered by DELETE")));
303+
rettup = trigdata->tg_trigtuple;
304+
}
305+
else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
306+
{
307+
ereport(NOTICE, (errmsg("triggered by UPDATE")));
308+
rettup = trigdata->tg_trigtuple;
309+
}
310+
else if (TRIGGER_FIRED_BY_TRUNCATE(trigdata->tg_event))
311+
{
312+
ereport(NOTICE, (errmsg("triggered by TRUNCATE")));
313+
rettup = trigdata->tg_trigtuple;
314+
}
315+
else
316+
elog(ERROR, "unrecognized event: %u", trigdata->tg_event);
317+
318+
if (TRIGGER_FIRED_BEFORE(trigdata->tg_event))
319+
ereport(NOTICE, (errmsg("triggered BEFORE")));
320+
else if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
321+
ereport(NOTICE, (errmsg("triggered AFTER")));
322+
else if (TRIGGER_FIRED_INSTEAD(trigdata->tg_event))
323+
ereport(NOTICE, (errmsg("triggered INSTEAD OF")));
324+
else
325+
elog(ERROR, "unrecognized when: %u", trigdata->tg_event);
326+
327+
if (TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
328+
ereport(NOTICE, (errmsg("triggered per row")));
329+
else if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
330+
ereport(NOTICE, (errmsg("triggered per statement")));
331+
else
332+
elog(ERROR, "unrecognized level: %u", trigdata->tg_event);
333+
334+
/*
335+
* Iterate through all of the trigger arguments, printing each input
336+
* value.
337+
*/
338+
for (int i = 0; i < trigdata->tg_trigger->tgnargs; i++)
339+
ereport(NOTICE,
340+
(errmsg("trigger arg[%i]: %s", i,
341+
trigdata->tg_trigger->tgargs[i])));
342+
}
343+
PG_CATCH();
344+
{
345+
/* Error cleanup code would go here */
346+
PG_RE_THROW();
347+
}
348+
PG_END_TRY();
349+
350+
if (SPI_finish() != SPI_OK_FINISH)
351+
elog(ERROR, "SPI_finish() failed");
352+
353+
return rettup;
354+
}

‎src/test/modules/plsample/sql/plsample.sql

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -13,3 +13,26 @@ AS $$
1313
Example of source with void result.
1414
$$ LANGUAGE plsample;
1515
SELECT plsample_result_void('{foo, bar, hoge}');
16+
17+
CREATE FUNCTION my_trigger_func() RETURNS trigger AS $$
18+
if TD_event == "INSERT"
19+
return TD_NEW
20+
elseif TD_event == "UPDATE"
21+
return TD_NEW
22+
else
23+
return "OK"
24+
end
25+
$$ language plsample;
26+
27+
CREATE TABLE my_table (num integer, description text);
28+
CREATE TRIGGER my_trigger_func BEFORE INSERT OR UPDATE ON my_table
29+
FOR EACH ROW EXECUTE FUNCTION my_trigger_func();
30+
CREATE TRIGGER my_trigger_func2 AFTER INSERT OR UPDATE ON my_table
31+
FOR EACH ROW EXECUTE FUNCTION my_trigger_func(8);
32+
33+
INSERT INTO my_table (num, description)
34+
VALUES (1, 'first');
35+
36+
UPDATE my_table
37+
SET description = 'first, modified once'
38+
WHERE num = 1;

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