131 lines
3.7 KiB
C
131 lines
3.7 KiB
C
/*
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moddatetime.c
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contrib/spi/moddatetime.c
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What is this?
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It is a function to be called from a trigger for the purpose of updating
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a modification datetime stamp in a record when that record is UPDATEd.
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Credits
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This is 95%+ based on autoinc.c, which I used as a starting point as I do
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not really know what I am doing. I also had help from
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Jan Wieck <jwieck@debis.com> who told me about the timestamp_in("now") function.
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OH, me, I'm Terry Mackintosh <terry@terrym.com>
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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 "catalog/pg_type.h"
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#include "commands/trigger.h"
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#include "executor/spi.h"
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#include "utils/builtins.h"
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#include "utils/rel.h"
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PG_MODULE_MAGIC;
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PG_FUNCTION_INFO_V1(moddatetime);
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Datum
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moddatetime(PG_FUNCTION_ARGS)
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{
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TriggerData *trigdata = (TriggerData *) fcinfo->context;
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Trigger *trigger; /* to get trigger name */
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int nargs; /* # of arguments */
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int attnum; /* positional number of field to change */
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Oid atttypid; /* type OID of field to change */
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Datum newdt; /* The current datetime. */
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bool newdtnull; /* null flag for it */
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char **args; /* arguments */
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char *relname; /* triggered relation name */
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Relation rel; /* triggered relation */
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HeapTuple rettuple = NULL;
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TupleDesc tupdesc; /* tuple description */
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if (!CALLED_AS_TRIGGER(fcinfo))
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/* internal error */
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elog(ERROR, "moddatetime: not fired by trigger manager");
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if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "moddatetime: must be fired for row");
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if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "moddatetime: must be fired before event");
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if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "moddatetime: cannot process INSERT events");
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else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
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rettuple = trigdata->tg_newtuple;
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else
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/* internal error */
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elog(ERROR, "moddatetime: cannot process DELETE events");
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rel = trigdata->tg_relation;
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relname = SPI_getrelname(rel);
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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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/* internal error */
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elog(ERROR, "moddatetime (%s): A single argument was expected", relname);
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args = trigger->tgargs;
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/* must be the field layout? */
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tupdesc = rel->rd_att;
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/*
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* This gets the position in the tuple of the field we want. args[0] being
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* the name of the field to update, as passed in from the trigger.
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*/
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attnum = SPI_fnumber(tupdesc, args[0]);
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/*
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* This is where we check to see if the field we are supposed to update
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* even exists.
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*/
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if (attnum <= 0)
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ereport(ERROR,
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(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
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errmsg("\"%s\" has no attribute \"%s\"",
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relname, args[0])));
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/*
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* Check the target field has an allowed type, and get the current
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* datetime as a value of that type.
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*/
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atttypid = SPI_gettypeid(tupdesc, attnum);
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if (atttypid == TIMESTAMPOID)
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newdt = DirectFunctionCall3(timestamp_in,
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CStringGetDatum("now"),
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ObjectIdGetDatum(InvalidOid),
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Int32GetDatum(-1));
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else if (atttypid == TIMESTAMPTZOID)
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newdt = DirectFunctionCall3(timestamptz_in,
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CStringGetDatum("now"),
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ObjectIdGetDatum(InvalidOid),
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Int32GetDatum(-1));
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else
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{
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ereport(ERROR,
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(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
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errmsg("attribute \"%s\" of \"%s\" must be type TIMESTAMP or TIMESTAMPTZ",
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args[0], relname)));
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newdt = (Datum) 0; /* keep compiler quiet */
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}
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newdtnull = false;
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/* Replace the attnum'th column with newdt */
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rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc,
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1, &attnum, &newdt, &newdtnull);
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/* Clean up */
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pfree(relname);
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return PointerGetDatum(rettuple);
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}
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