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Standard English uses "may", "can", and "might" in different ways:
may - permission, "You may borrow my rake."
can - ability, "I can lift that log."
might - possibility, "It might rain today."
Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".
94 lines
2.7 KiB
C
94 lines
2.7 KiB
C
/*
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* insert_username.c
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* $Modified: Thu Oct 16 08:13:42 1997 by brook $
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* $PostgreSQL: pgsql/contrib/spi/insert_username.c,v 1.15 2007/02/01 19:10:23 momjian Exp $
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*
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* insert user name in response to a trigger
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* usage: insert_username (column_name)
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*/
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#include "executor/spi.h" /* this is what you need to work with SPI */
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#include "commands/trigger.h" /* -"- and triggers */
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#include "miscadmin.h" /* for GetUserName() */
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PG_MODULE_MAGIC;
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extern Datum insert_username(PG_FUNCTION_ARGS);
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PG_FUNCTION_INFO_V1(insert_username);
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Datum
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insert_username(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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Datum newval; /* new value of column */
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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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int attnum;
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/* sanity checks from autoinc.c */
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if (!CALLED_AS_TRIGGER(fcinfo))
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/* internal error */
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elog(ERROR, "insert_username: not fired by trigger manager");
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if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "insert_username: cannot process STATEMENT events");
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if (TRIGGER_FIRED_AFTER(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "insert_username: must be fired before event");
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if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
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rettuple = trigdata->tg_trigtuple;
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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, "insert_username: 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, "insert_username (%s): one argument was expected", relname);
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args = trigger->tgargs;
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tupdesc = rel->rd_att;
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attnum = SPI_fnumber(tupdesc, args[0]);
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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\"", relname, args[0])));
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if (SPI_gettypeid(tupdesc, attnum) != TEXTOID)
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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 TEXT",
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args[0], relname)));
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/* create fields containing name */
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newval = DirectFunctionCall1(textin,
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CStringGetDatum(GetUserNameFromId(GetUserId())));
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/* construct new tuple */
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rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, &newval, NULL);
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if (rettuple == NULL)
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/* internal error */
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elog(ERROR, "insert_username (\"%s\"): %d returned by SPI_modifytuple",
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relname, SPI_result);
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pfree(relname);
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return PointerGetDatum(rettuple);
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}
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