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https://git.postgresql.org/git/postgresql.git
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186 lines
5.0 KiB
C
186 lines
5.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* tcn.c
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* triggered change notification support for PostgreSQL
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*
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* Portions Copyright (c) 2011-2014, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* contrib/tcn/tcn.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/htup_details.h"
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#include "executor/spi.h"
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#include "commands/async.h"
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#include "commands/trigger.h"
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#include "lib/stringinfo.h"
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#include "utils/rel.h"
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#include "utils/syscache.h"
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PG_MODULE_MAGIC;
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/* forward declarations */
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Datum triggered_change_notification(PG_FUNCTION_ARGS);
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/*
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* Copy from s (for source) to r (for result), wrapping with q (quote)
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* characters and doubling any quote characters found.
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*/
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static void
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strcpy_quoted(StringInfo r, const char *s, const char q)
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{
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appendStringInfoCharMacro(r, q);
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while (*s)
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{
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if (*s == q)
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appendStringInfoCharMacro(r, q);
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appendStringInfoCharMacro(r, *s);
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s++;
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}
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appendStringInfoCharMacro(r, q);
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}
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/*
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* triggered_change_notification
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*
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* This trigger function will send a notification of data modification with
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* primary key values. The channel will be "tcn" unless the trigger is
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* created with a parameter, in which case that parameter will be used.
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*/
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PG_FUNCTION_INFO_V1(triggered_change_notification);
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Datum
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triggered_change_notification(PG_FUNCTION_ARGS)
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{
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TriggerData *trigdata = (TriggerData *) fcinfo->context;
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Trigger *trigger;
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int nargs;
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HeapTuple trigtuple;
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Relation rel;
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TupleDesc tupdesc;
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char *channel;
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char operation;
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StringInfo payload = makeStringInfo();
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bool foundPK;
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List *indexoidlist;
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ListCell *indexoidscan;
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/* make sure it's called as a trigger */
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if (!CALLED_AS_TRIGGER(fcinfo))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("triggered_change_notification: must be called as trigger")));
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/* and that it's called after the change */
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if (!TRIGGER_FIRED_AFTER(trigdata->tg_event))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("triggered_change_notification: must be called after the change")));
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/* and that it's called for each row */
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if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("triggered_change_notification: must be called for each row")));
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if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
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operation = 'I';
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else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
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operation = 'U';
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else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
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operation = 'D';
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else
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{
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elog(ERROR, "triggered_change_notification: trigger fired by unrecognized operation");
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operation = 'X'; /* silence compiler warning */
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}
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trigger = trigdata->tg_trigger;
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nargs = trigger->tgnargs;
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if (nargs > 1)
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("triggered_change_notification: must not be called with more than one parameter")));
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if (nargs == 0)
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channel = "tcn";
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else
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channel = trigger->tgargs[0];
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/* get tuple data */
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trigtuple = trigdata->tg_trigtuple;
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rel = trigdata->tg_relation;
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tupdesc = rel->rd_att;
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foundPK = false;
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/*
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* Get the list of index OIDs for the table from the relcache, and look up
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* each one in the pg_index syscache until we find one marked primary key
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* (hopefully there isn't more than one such).
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*/
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indexoidlist = RelationGetIndexList(rel);
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foreach(indexoidscan, indexoidlist)
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{
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Oid indexoid = lfirst_oid(indexoidscan);
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HeapTuple indexTuple;
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Form_pg_index index;
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indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
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if (!HeapTupleIsValid(indexTuple)) /* should not happen */
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elog(ERROR, "cache lookup failed for index %u", indexoid);
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index = (Form_pg_index) GETSTRUCT(indexTuple);
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/* we're only interested if it is the primary key and valid */
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if (index->indisprimary && IndexIsValid(index))
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{
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int numatts = index->indnatts;
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if (numatts > 0)
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{
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int i;
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foundPK = true;
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strcpy_quoted(payload, RelationGetRelationName(rel), '"');
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appendStringInfoCharMacro(payload, ',');
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appendStringInfoCharMacro(payload, operation);
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for (i = 0; i < numatts; i++)
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{
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int colno = index->indkey.values[i];
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appendStringInfoCharMacro(payload, ',');
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strcpy_quoted(payload, NameStr((tupdesc->attrs[colno - 1])->attname), '"');
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appendStringInfoCharMacro(payload, '=');
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strcpy_quoted(payload, SPI_getvalue(trigtuple, tupdesc, colno), '\'');
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}
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Async_Notify(channel, payload->data);
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}
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ReleaseSysCache(indexTuple);
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break;
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}
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ReleaseSysCache(indexTuple);
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}
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list_free(indexoidlist);
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if (!foundPK)
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ereport(ERROR,
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(errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
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errmsg("triggered_change_notification: must be called on a table with a primary key")));
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return PointerGetDatum(NULL); /* after trigger; value doesn't matter */
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}
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