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113 lines
2.9 KiB
C
113 lines
2.9 KiB
C
/*
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* noup.c -- functions to remove update permission from a column
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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 <ctype.h> /* tolower () */
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extern Datum noup(PG_FUNCTION_ARGS);
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/*
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* noup () -- revoke permission on column
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*
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* Though it's called without args You have to specify referenced
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* table/column while creating trigger:
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* EXECUTE PROCEDURE noup ('col').
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*/
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PG_FUNCTION_INFO_V1(noup);
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Datum
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noup(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 args specified in CREATE TRIGGER */
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char **args; /* arguments: column names and table name */
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int nkeys; /* # of key columns (= nargs / 2) */
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Datum *kvals; /* key values */
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Relation rel; /* triggered relation */
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HeapTuple tuple = NULL; /* tuple to return */
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TupleDesc tupdesc; /* tuple description */
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bool isnull; /* to know is some column NULL or not */
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int ret;
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int i;
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/*
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* Some checks first...
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*/
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/* Called by trigger manager ? */
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if (!CALLED_AS_TRIGGER(fcinfo))
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/* internal error */
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elog(ERROR, "noup: not fired by trigger manager");
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/* Should be called for ROW trigger */
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if (TRIGGER_FIRED_FOR_STATEMENT(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "noup: can't process STATEMENT events");
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/* Should not be called for INSERT */
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if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "noup: can't process INSERT events");
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/* Should not be called for DELETE */
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else if (TRIGGER_FIRED_BY_DELETE(trigdata->tg_event))
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/* internal error */
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elog(ERROR, "noup: can't process DELETE events");
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/* check new Tuple */
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tuple = trigdata->tg_newtuple;
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trigger = trigdata->tg_trigger;
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nargs = trigger->tgnargs;
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args = trigger->tgargs;
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nkeys = nargs;
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rel = trigdata->tg_relation;
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tupdesc = rel->rd_att;
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/* Connect to SPI manager */
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if ((ret = SPI_connect()) < 0)
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/* internal error */
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elog(ERROR, "noup: SPI_connect returned %d", ret);
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/*
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* We use SPI plan preparation feature, so allocate space to place key
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* values.
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*/
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kvals = (Datum *) palloc(nkeys * sizeof(Datum));
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/* For each column in key ... */
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for (i = 0; i < nkeys; i++)
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{
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/* get index of column in tuple */
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int fnumber = SPI_fnumber(tupdesc, args[i]);
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/* Bad guys may give us un-existing column in CREATE TRIGGER */
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if (fnumber < 0)
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/* internal error */
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elog(ERROR, "noup: there is no attribute %s in relation %s",
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args[i], SPI_getrelname(rel));
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/* Well, get binary (in internal format) value of column */
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kvals[i] = SPI_getbinval(tuple, tupdesc, fnumber, &isnull);
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/*
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* If it's NOT NULL then cancel update
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*/
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if (!isnull)
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{
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elog(WARNING, "%s: update not allowed", args[i]);
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SPI_finish();
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return PointerGetDatum(NULL);
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}
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}
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SPI_finish();
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return PointerGetDatum(tuple);
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}
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