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/*-------------------------------------------------------------------------
*
* tcn.c
* triggered change notification support for PostgreSQL
*
* Portions Copyright (c) 2011-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* contrib/tcn/tcn.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/htup_details.h"
#include "commands/async.h"
#include "commands/trigger.h"
#include "executor/spi.h"
#include "lib/stringinfo.h"
#include "utils/rel.h"
#include "utils/syscache.h"
PG_MODULE_MAGIC;
/*
* Copy from s (for source) to r (for result), wrapping with q (quote)
* characters and doubling any quote characters found.
*/
static void
strcpy_quoted(StringInfo r, const char *s, const char q)
{
appendStringInfoCharMacro(r, q);
while (*s)
{
if (*s == q)
appendStringInfoCharMacro(r, q);
appendStringInfoCharMacro(r, *s);
s++;
}
appendStringInfoCharMacro(r, q);
}
/*
* triggered_change_notification
*
* This trigger function will send a notification of data modification with
* primary key values. The channel will be "tcn" unless the trigger is
* created with a parameter, in which case that parameter will be used.
*/
PG_FUNCTION_INFO_V1(triggered_change_notification);
Datum
triggered_change_notification(PG_FUNCTION_ARGS)
{
TriggerData *trigdata = (TriggerData *) fcinfo->context;
Trigger *trigger;
int nargs;
HeapTuple trigtuple;
Relation rel;
TupleDesc tupdesc;
char *channel;
char operation;
StringInfo payload = makeStringInfo();
bool foundPK;
List *indexoidlist;
ListCell *indexoidscan;
/* make sure it's called as a trigger */
if (!CALLED_AS_TRIGGER(fcinfo))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("triggered_change_notification: must be called as trigger")));
/* and that it's called after the change */
if (!TRIGGER_FIRED_AFTER(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("triggered_change_notification: must be called after the change")));
/* and that it's called for each row */
if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("triggered_change_notification: must be called for each row")));
if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
operation = 'I';
else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
operation = 'U';
else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
operation = 'D';
else
{
elog(ERROR, "triggered_change_notification: trigger fired by unrecognized operation");
operation = 'X'; /* silence compiler warning */
}
trigger = trigdata->tg_trigger;
nargs = trigger->tgnargs;
if (nargs > 1)
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("triggered_change_notification: must not be called with more than one parameter")));
if (nargs == 0)
channel = "tcn";
else
channel = trigger->tgargs[0];
/* get tuple data */
trigtuple = trigdata->tg_trigtuple;
rel = trigdata->tg_relation;
tupdesc = rel->rd_att;
foundPK = false;
/*
* Get the list of index OIDs for the table from the relcache, and look up
* each one in the pg_index syscache until we find one marked primary key
* (hopefully there isn't more than one such).
*/
indexoidlist = RelationGetIndexList(rel);
foreach(indexoidscan, indexoidlist)
{
Oid indexoid = lfirst_oid(indexoidscan);
HeapTuple indexTuple;
Form_pg_index index;
indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
if (!HeapTupleIsValid(indexTuple)) /* should not happen */
elog(ERROR, "cache lookup failed for index %u", indexoid);
index = (Form_pg_index) GETSTRUCT(indexTuple);
/* we're only interested if it is the primary key and valid */
if (index->indisprimary && index->indisvalid)
{
int indnkeyatts = index->indnkeyatts;
if (indnkeyatts > 0)
{
int i;
foundPK = true;
strcpy_quoted(payload, RelationGetRelationName(rel), '"');
appendStringInfoCharMacro(payload, ',');
appendStringInfoCharMacro(payload, operation);
for (i = 0; i < indnkeyatts; i++)
{
int colno = index->indkey.values[i];
Form_pg_attribute attr = TupleDescAttr(tupdesc, colno - 1);
appendStringInfoCharMacro(payload, ',');
strcpy_quoted(payload, NameStr(attr->attname), '"');
appendStringInfoCharMacro(payload, '=');
strcpy_quoted(payload, SPI_getvalue(trigtuple, tupdesc, colno), '\'');
}
Async_Notify(channel, payload->data);
}
ReleaseSysCache(indexTuple);
break;
}
ReleaseSysCache(indexTuple);
}
list_free(indexoidlist);
if (!foundPK)
ereport(ERROR,
(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
errmsg("triggered_change_notification: must be called on a table with a primary key")));
return PointerGetDatum(NULL); /* after trigger; value doesn't matter */
}
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