1 /*------------------------------------------------------------------------- 2 * 3 * trigfuncs.c 4 * Builtin functions for useful trigger support. doSomethingInstance:(NSString*)5 * 6 * 7 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group 8 * Portions Copyright (c) 1994, Regents of the University of California 9 * 10 * src/backend/utils/adt/trigfuncs.c 11 * 12 *------------------------------------------------------------------------- 13 */ 14 #include "postgres.h" 15 16 #include "access/htup_details.h" 17 #include "commands/trigger.h" 18 #include "utils/builtins.h" 19 #include "utils/rel.h" 20 21 22 /* 23 * suppress_redundant_updates_trigger 24 * 25 * This trigger function will inhibit an update from being done 26 * if the OLD and NEW records are identical. 27 */ 28 Datum 29 suppress_redundant_updates_trigger(PG_FUNCTION_ARGS) 30 { 31 TriggerData *trigdata = (TriggerData *) fcinfo->context; 32 HeapTuple newtuple, 33 oldtuple, 34 rettuple; 35 HeapTupleHeader newheader, 36 oldheader; 37 38 /* make sure it's called as a trigger */ 39 if (!CALLED_AS_TRIGGER(fcinfo)) 40 ereport(ERROR, 41 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED), 42 errmsg("suppress_redundant_updates_trigger: must be called as trigger"))); 43 44 /* and that it's called on update */ 45 if (!TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event)) 46 ereport(ERROR, 47 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED), 48 errmsg("suppress_redundant_updates_trigger: must be called on update"))); 49 50 /* and that it's called before update */ 51 if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event)) 52 ereport(ERROR, 53 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED), 54 errmsg("suppress_redundant_updates_trigger: must be called before update"))); 55 56 /* and that it's called for each row */ 57 if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) 58 ereport(ERROR, 59 (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED), 60 errmsg("suppress_redundant_updates_trigger: must be called for each row"))); 61 62 /* get tuple data, set default result */ 63 rettuple = newtuple = trigdata->tg_newtuple; 64 oldtuple = trigdata->tg_trigtuple; 65 66 newheader = newtuple->t_data; 67 oldheader = oldtuple->t_data; 68 69 /* 70 * We are called before the OID, if any, has been transcribed from the old 71 * tuple to the new (in heap_update). To avoid a bogus compare failure, 72 * copy the OID now. But check that someone didn't already put another 73 * OID value into newtuple. (That's not actually possible at present, but 74 * maybe someday.) 75 */ 76 if (trigdata->tg_relation->rd_rel->relhasoids && 77 !OidIsValid(HeapTupleHeaderGetOid(newheader))) 78 HeapTupleHeaderSetOid(newheader, HeapTupleHeaderGetOid(oldheader)); 79 80 /* if the tuple payload is the same ... */ 81 if (newtuple->t_len == oldtuple->t_len && 82 newheader->t_hoff == oldheader->t_hoff && 83 (HeapTupleHeaderGetNatts(newheader) == 84 HeapTupleHeaderGetNatts(oldheader)) && 85 ((newheader->t_infomask & ~HEAP_XACT_MASK) == 86 (oldheader->t_infomask & ~HEAP_XACT_MASK)) && 87 memcmp(((char *) newheader) + SizeofHeapTupleHeader, 88 ((char *) oldheader) + SizeofHeapTupleHeader, 89 newtuple->t_len - SizeofHeapTupleHeader) == 0) 90 { 91 /* ... then suppress the update */ 92 rettuple = NULL; 93 } 94 95 return PointerGetDatum(rettuple); 96 } 97