General trigger functions for referential integrity.

contrib/spi/Makefile

+
+SRCDIR= /home/postgres/current/pgsql/src
+
+include $(SRCDIR)/Makefile.global
+
+CFLAGS+= $(CFLAGS_SL) -I$(SRCDIR)/include -DREFINT_QUIET
+
+TARGETS= refint$(DLSUFFIX) refint.sql
+
+CLEANFILES+= $(TARGETS)
+
+all:: $(TARGETS)
+
+%.sql: %.source
+	rm -f $@; \
+	C=`pwd`; \
+	sed -e "s:_OBJWD_:$$C:g" \
+	    -e "s:_DLSUFFIX_:$(DLSUFFIX):g" < $< > $@
+
+clean: 
+	rm -f $(TARGETS)

contrib/spi/refint.c

+/*
+ * refint.c --	set of functions to define referential integrity
+ *		constraints using general triggers.
+ */
+
+#include "executor/spi.h"		/* this is what you need to work with SPI */
+#include "commands/trigger.h"	/* -"- and triggers */
+#include <ctype.h>				/* tolower () */
+
+HeapTuple	check_primary_key(void);
+HeapTuple	check_foreign_key(void);
+
+
+typedef struct
+{
+	char	   *ident;
+	int			nplans;
+	void	  **splan;
+}			EPlan;
+
+static EPlan *FPlans = NULL;
+static int	nFPlans = 0;
+static EPlan *PPlans = NULL;
+static int	nPPlans = 0;
+
+static EPlan *find_plan(char *ident, EPlan ** eplan, int *nplans);
+
+/*
+ * check_primary_key () -- check that key in tuple being inserted/updated
+ *			 references existing tuple in "primary" table.
+ * Though it's called without args You have to specify referenced
+ * table/keys while creating trigger:  key field names in triggered table,
+ * referenced table name, referenced key field names:
+ * EXECUTE PROCEDURE
+ * check_primary_key ('Fkey1', 'Fkey2', 'Ptable', 'Pkey1', 'Pkey2').
+ */
+
+HeapTuple						/* have to return HeapTuple to Executor */
+check_primary_key()
+{
+	Trigger    *trigger;		/* to get trigger name */
+	int			nargs;			/* # of args specified in CREATE TRIGGER */
+	char	  **args;			/* arguments: column names and table name */
+	int			nkeys;			/* # of key columns (= nargs / 2) */
+	char	  **kvals;			/* key values */
+	char	   *relname;		/* referenced relation name */
+	Relation	rel;			/* triggered relation */
+	HeapTuple	tuple = NULL;	/* tuple to return */
+	TupleDesc	tupdesc;		/* tuple description */
+	EPlan	   *plan;			/* prepared plan */
+	Oid		   *argtypes = NULL;/* key types to prepare execution plan */
+	bool		isnull;			/* to know is some column NULL or not */
+	char		ident[2 * NAMEDATALEN]; /* to identify myself */
+	int			ret;
+	int			i;
+
+	/*
+	 * Some checks first...
+	 */
+
+	/* Called by trigger manager ? */
+	if (!CurrentTriggerData)
+		elog(WARN, "check_primary_key: triggers are not initialized");
+
+	/* Should be called for ROW trigger */
+	if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
+		elog(WARN, "check_primary_key: can't process STATEMENT events");
+
+	/* If INSERTion then must check Tuple to being inserted */
+	if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
+
+		tuple = CurrentTriggerData->tg_trigtuple;
+
+	/* Not should be called for DELETE */
+	else if (TRIGGER_FIRED_BY_DELETE(CurrentTriggerData->tg_event))
+
+		elog(WARN, "check_primary_key: can't process DELETE events");
+
+	/* If UPDATion the must check new Tuple, not old one */
+	else
+		tuple = CurrentTriggerData->tg_newtuple;
+
+	trigger = CurrentTriggerData->tg_trigger;
+	nargs = trigger->tgnargs;
+	args = trigger->tgargs;
+
+	if (nargs % 2 != 1)			/* odd number of arguments! */
+		elog(WARN, "check_primary_key: odd number of arguments should be specified");
+
+	nkeys = nargs / 2;
+	relname = args[nkeys];
+	rel = CurrentTriggerData->tg_relation;
+	tupdesc = rel->rd_att;
+
+	/*
+	 * Setting CurrentTriggerData to NULL prevents direct calls to trigger
+	 * functions in queries. Normally, trigger functions have to be called
+	 * by trigger manager code only.
+	 */
+	CurrentTriggerData = NULL;
+
+	/* Connect to SPI manager */
+	if ((ret = SPI_connect()) < 0)
+		elog(WARN, "check_primary_key: SPI_connect returned %d", ret);
+
+	/*
+	 * We use SPI plan preparation feature, so allocate space to place key
+	 * values.
+	 */
+	kvals = (char **) palloc(nkeys * sizeof(char *));
+
+	/*
+	 * Construct ident string as TriggerName $ TriggeredRelationId and try
+	 * to find prepared execution plan.
+	 */
+	sprintf(ident, "%s$%u", trigger->tgname, rel->rd_id);
+	plan = find_plan(ident, &PPlans, &nPPlans);
+
+	/* if there is no plan then allocate argtypes for preparation */
+	if (plan->nplans <= 0)
+		argtypes = (Oid *) palloc(nkeys * sizeof(Oid));
+
+	/* For each column in key ... */
+	for (i = 0; i < nkeys; i++)
+	{
+		/* get index of column in tuple */
+		int			fnumber = SPI_fnumber(tupdesc, args[i]);
+
+		/* Bad guys may give us un-existing column in CREATE TRIGGER */
+		if (fnumber < 0)
+			elog(WARN, "check_primary_key: there is no attribute %s in relation %s",
+				 args[i], SPI_getrelname(rel));
+
+		/* Well, get binary (in internal format) value of column */
+		kvals[i] = SPI_getbinval(tuple, tupdesc, fnumber, &isnull);
+
+		/*
+		 * If it's NULL then nothing to do! DON'T FORGET call SPI_finish
+		 * ()! DON'T FORGET return tuple! Executor inserts tuple you're
+		 * returning! If you return NULL then nothing will be inserted!
+		 */
+		if (isnull)
+		{
+			SPI_finish();
+			return (tuple);
+		}
+
+		if (plan->nplans <= 0)	/* Get typeId of column */
+			argtypes[i] = SPI_gettypeid(tupdesc, fnumber);
+	}
+
+	/*
+	 * If we have to prepare plan ...
+	 */
+	if (plan->nplans <= 0)
+	{
+		void	   *pplan;
+		char		sql[8192];
+
+		/*
+		 * Construct query: SELECT 1 FROM _referenced_relation_ WHERE
+		 * Pkey1 = $1 [AND Pkey2 = $2 [...]]
+		 */
+		sprintf(sql, "select 1 from %s where ", relname);
+		for (i = 0; i < nkeys; i++)
+		{
+			sprintf(sql + strlen(sql), "%s = $%d %s",
+			  args[i + nkeys + 1], i + 1, (i < nkeys - 1) ? "and " : "");
+		}
+
+		/* Prepare plan for query */
+		pplan = SPI_prepare(sql, nkeys, argtypes);
+		if (pplan == NULL)
+			elog(WARN, "check_primary_key: SPI_prepare returned %d", SPI_result);
+
+		/*
+		 * Remember that SPI_prepare places plan in current memory context
+		 * - so, we have to save plan in Top memory context for latter
+		 * use.
+		 */
+		pplan = SPI_saveplan(pplan);
+		if (pplan == NULL)
+			elog(WARN, "check_primary_key: SPI_saveplan returned %d", SPI_result);
+		plan->splan = (void **) malloc(sizeof(void *));
+		*(plan->splan) = pplan;
+		plan->nplans = 1;
+	}
+
+	/*
+	 * Ok, execute prepared plan.
+	 */
+	ret = SPI_execp(*(plan->splan), kvals, NULL, 1);
+		/* we have no NULLs - so we pass   ^^^^   here */
+
+	if (ret < 0)
+		elog(WARN, "check_primary_key: SPI_execp returned %d", ret);
+
+	/*
+	 * If there are no tuples returned by SELECT then ...
+	 */
+	if (SPI_processed == 0)
+		elog(WARN, "%s: tuple references non-existing key in %s",
+			 trigger->tgname, relname);
+
+	SPI_finish();
+
+	return (tuple);
+}
+
+/*
+ * check_foreign_key () -- check that key in tuple being deleted/updated
+ *			 is not referenced by tuples in "foreign" table(s).
+ * Though it's called without args You have to specify (while creating trigger):
+ * number of references, action to do if key referenced
+ * ('restrict' | 'setnull' | 'cascade'), key field names in triggered
+ * ("primary") table and referencing table(s)/keys:
+ * EXECUTE PROCEDURE
+ * check_foreign_key (2, 'restrict', 'Pkey1', 'Pkey2',
+ * 'Ftable1', 'Fkey11', 'Fkey12', 'Ftable2', 'Fkey21', 'Fkey22').
+ */
+
+HeapTuple						/* have to return HeapTuple to Executor */
+check_foreign_key()
+{
+	Trigger    *trigger;		/* to get trigger name */
+	int			nargs;			/* # of args specified in CREATE TRIGGER */
+	char	  **args;			/* arguments: as described above */
+	int			nrefs;			/* number of references (== # of plans) */
+	char		action;			/* 'R'estrict | 'S'etnull | 'C'ascade */
+	int			nkeys;			/* # of key columns */
+	char	  **kvals;			/* key values */
+	char	   *relname;		/* referencing relation name */
+	Relation	rel;			/* triggered relation */
+	HeapTuple	trigtuple = NULL;		/* tuple to being changed */
+	HeapTuple	newtuple = NULL;/* tuple to return */
+	TupleDesc	tupdesc;		/* tuple description */
+	EPlan	   *plan;			/* prepared plan(s) */
+	Oid		   *argtypes = NULL;/* key types to prepare execution plan */
+	bool		isnull;			/* to know is some column NULL or not */
+	bool		isequal = true; /* are keys in both tuples equal (in
+								 * UPDATE) */
+	char		ident[2 * NAMEDATALEN]; /* to identify myself */
+	int			ret;
+	int			i,
+				r;
+
+	/*
+	 * Some checks first...
+	 */
+
+	/* Called by trigger manager ? */
+	if (!CurrentTriggerData)
+		elog(WARN, "check_foreign_key: triggers are not initialized");
+
+	/* Should be called for ROW trigger */
+	if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
+		elog(WARN, "check_foreign_key: can't process STATEMENT events");
+
+	/* Not should be called for INSERT */
+	if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
+
+		elog(WARN, "check_foreign_key: can't process INSERT events");
+
+	/* Have to check tg_trigtuple - tuple being deleted */
+	trigtuple = CurrentTriggerData->tg_trigtuple;
+
+	/*
+	 * But if this is UPDATE then we have to return tg_newtuple. Also, if
+	 * key in tg_newtuple is the same as in tg_trigtuple then nothing to
+	 * do.
+	 */
+	if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
+		newtuple = CurrentTriggerData->tg_newtuple;
+
+	trigger = CurrentTriggerData->tg_trigger;
+	nargs = trigger->tgnargs;
+	args = trigger->tgargs;
+
+	if (nargs < 5)				/* nrefs, action, key, Relation, key - at
+								 * least */
+		elog(WARN, "check_foreign_key: too short %d (< 5) list of arguments", nargs);
+	nrefs = pg_atoi(args[0], sizeof(int), 0);
+	if (nrefs < 1)
+		elog(WARN, "check_foreign_key: %d (< 1) number of references specified", nrefs);
+	action = tolower(*(args[1]));
+	if (action != 'r' && action != 'c' && action != 's')
+		elog(WARN, "check_foreign_key: invalid action %s", args[1]);
+	nargs -= 2;
+	args += 2;
+	nkeys = (nargs - nrefs) / (nrefs + 1);
+	if (nkeys <= 0 || nargs != (nrefs + nkeys * (nrefs + 1)))
+		elog(WARN, "check_foreign_key: invalid number of arguments %d for %d references",
+			 nargs + 2, nrefs);
+
+	rel = CurrentTriggerData->tg_relation;
+	tupdesc = rel->rd_att;
+
+	/*
+	 * Setting CurrentTriggerData to NULL prevents direct calls to trigger
+	 * functions in queries. Normally, trigger functions have to be called
+	 * by trigger manager code only.
+	 */
+	CurrentTriggerData = NULL;
+
+	/* Connect to SPI manager */
+	if ((ret = SPI_connect()) < 0)
+		elog(WARN, "check_foreign_key: SPI_connect returned %d", ret);
+
+	/*
+	 * We use SPI plan preparation feature, so allocate space to place key
+	 * values.
+	 */
+	kvals = (char **) palloc(nkeys * sizeof(char *));
+
+	/*
+	 * Construct ident string as TriggerName $ TriggeredRelationId and try
+	 * to find prepared execution plan(s).
+	 */
+	sprintf(ident, "%s$%u", trigger->tgname, rel->rd_id);
+	plan = find_plan(ident, &FPlans, &nFPlans);
+
+	/* if there is no plan(s) then allocate argtypes for preparation */
+	if (plan->nplans <= 0)
+		argtypes = (Oid *) palloc(nkeys * sizeof(Oid));
+
+	/*
+	 * else - check that we have exactly nrefs plan(s) ready
+	 */
+	else if (plan->nplans != nrefs)
+		elog(WARN, "%s: check_foreign_key: # of plans changed in meantime",
+			 trigger->tgname);
+
+	/* For each column in key ... */
+	for (i = 0; i < nkeys; i++)
+	{
+		/* get index of column in tuple */
+		int			fnumber = SPI_fnumber(tupdesc, args[i]);
+
+		/* Bad guys may give us un-existing column in CREATE TRIGGER */
+		if (fnumber < 0)
+			elog(WARN, "check_foreign_key: there is no attribute %s in relation %s",
+				 args[i], SPI_getrelname(rel));
+
+		/* Well, get binary (in internal format) value of column */
+		kvals[i] = SPI_getbinval(trigtuple, tupdesc, fnumber, &isnull);
+
+		/*
+		 * If it's NULL then nothing to do! DON'T FORGET call SPI_finish
+		 * ()! DON'T FORGET return tuple! Executor inserts tuple you're
+		 * returning! If you return NULL then nothing will be inserted!
+		 */
+		if (isnull)
+		{
+			SPI_finish();
+			return ((newtuple == NULL) ? trigtuple : newtuple);
+		}
+
+		/*
+		 * If UPDATE then get column value from new tuple being inserted
+		 * and compare is this the same as old one. For the moment we use
+		 * string presentation of values...
+		 */
+		if (newtuple != NULL)
+		{
+			char	   *oldval = SPI_getvalue(trigtuple, tupdesc, fnumber);
+			char	   *newval;
+
+			/* this shouldn't happen! SPI_ERROR_NOOUTFUNC ? */
+			if (oldval == NULL)
+				elog(WARN, "check_foreign_key: SPI_getvalue returned %d", SPI_result);
+			newval = SPI_getvalue(newtuple, tupdesc, fnumber);
+			if (newval == NULL || strcmp(oldval, newval) != 0)
+				isequal = false;
+		}
+
+		if (plan->nplans <= 0)	/* Get typeId of column */
+			argtypes[i] = SPI_gettypeid(tupdesc, fnumber);
+	}
+	nargs -= nkeys;
+	args += nkeys;
+
+	/*
+	 * If we have to prepare plans ...
+	 */
+	if (plan->nplans <= 0)
+	{
+		void	   *pplan;
+		char		sql[8192];
+		char	  **args2 = args;
+
+		plan->splan = (void **) malloc(nrefs * sizeof(void *));
+
+		for (r = 0; r < nrefs; r++)
+		{
+			relname = args2[0];
+
+			/*
+			 * For 'R'estrict action we construct SELECT query - SELECT 1
+			 * FROM _referencing_relation_ WHERE Fkey1 = $1 [AND Fkey2 =
+			 * $2 [...]] - to check is tuple referenced or not.
+			 */
+			if (action == 'r')
+
+				sprintf(sql, "select 1 from %s where ", relname);
+
+			/*
+			 * For 'C'ascade action we construct DELETE query - DELETE
+			 * FROM _referencing_relation_ WHERE Fkey1 = $1 [AND Fkey2 =
+			 * $2 [...]] - to delete all referencing tuples.
+			 */
+			else if (action == 'c')
+
+				sprintf(sql, "delete from %s where ", relname);
+
+			/*
+			 * For 'S'etnull action we construct UPDATE query - UPDATE
+			 * _referencing_relation_ SET Fkey1 null [, Fkey2 null [...]]
+			 * WHERE Fkey1 = $1 [AND Fkey2 = $2 [...]] - to set key
+			 * columns in all referencing tuples to NULL.
+			 */
+			else if (action == 's')
+			{
+				sprintf(sql, "update %s set ", relname);
+				for (i = 1; i <= nkeys; i++)
+				{
+					sprintf(sql + strlen(sql), "%s null%s",
+							args2[i], (i < nkeys) ? ", " : "");
+				}
+				strcat(sql, " where ");
+			}
+
+			/* Construct WHERE qual */
+			for (i = 1; i <= nkeys; i++)
+			{
+				sprintf(sql + strlen(sql), "%s = $%d %s",
+						args2[i], i, (i < nkeys) ? "and " : "");
+			}
+
+			/* Prepare plan for query */
+			pplan = SPI_prepare(sql, nkeys, argtypes);
+			if (pplan == NULL)
+				elog(WARN, "check_foreign_key: SPI_prepare returned %d", SPI_result);
+
+			/*
+			 * Remember that SPI_prepare places plan in current memory
+			 * context - so, we have to save plan in Top memory context
+			 * for latter use.
+			 */
+			pplan = SPI_saveplan(pplan);
+			if (pplan == NULL)
+				elog(WARN, "check_foreign_key: SPI_saveplan returned %d", SPI_result);
+
+			plan->splan[r] = pplan;
+
+			args2 += nkeys + 1; /* to the next relation */
+		}
+		plan->nplans = nrefs;
+	}
+
+	/*
+	 * If UPDATE and key is not changed ...
+	 */
+	if (newtuple != NULL && isequal)
+	{
+		SPI_finish();
+		return (newtuple);
+	}
+
+	/*
+	 * Ok, execute prepared plan(s).
+	 */
+	for (r = 0; r < nrefs; r++)
+	{
+
+		/*
+		 * For 'R'estrict we may to execute plan for one tuple only, for
+		 * other actions - for all tuples.
+		 */
+		int			tcount = (action == 'r') ? 1 : 0;
+
+		relname = args[0];
+
+		ret = SPI_execp(plan->splan[r], kvals, NULL, tcount);
+			/* we have no NULLs - so we pass   ^^^^	 here */
+
+		if (ret < 0)
+			elog(WARN, "check_foreign_key: SPI_execp returned %d", ret);
+
+		/* If action is 'R'estrict ... */
+		if (action == 'r')
+		{
+			/* If there is tuple returned by SELECT then ... */
+			if (SPI_processed > 0)
+				elog(WARN, "%s: tuple referenced in %s",
+					 trigger->tgname, relname);
+		}
+#ifndef REFINT_QUIET
+		else
+			elog(NOTICE, "%s: %d tuple(s) of %s are %s",
+				 trigger->tgname, SPI_processed, relname,
+				 (action == 'c') ? "deleted" : "setted to null");
+#endif
+		args += nkeys + 1;		/* to the next relation */
+	}
+
+	SPI_finish();
+
+	return ((newtuple == NULL) ? trigtuple : newtuple);
+}
+
+static EPlan *
+find_plan(char *ident, EPlan ** eplan, int *nplans)
+{
+	EPlan	   *newp;
+	int			i;
+
+	if (*nplans > 0)
+	{
+		for (i = 0; i < *nplans; i++)
+		{
+			if (strcmp((*eplan)[i].ident, ident) == 0)
+				break;
+		}
+		if (i != *nplans)
+			return (*eplan + i);
+		*eplan = (EPlan *) realloc(*eplan, (i + 1) * sizeof(EPlan));
+		newp = *eplan + i;
+	}
+	else
+	{
+		newp = *eplan = (EPlan *) malloc(sizeof(EPlan));
+		(*nplans) = i = 0;
+	}
+
+	newp->ident = (char *) malloc(strlen(ident) + 1);
+	strcpy(newp->ident, ident);
+	newp->nplans = 0;
+	newp->splan = NULL;
+	(*nplans)++;
+
+	return (newp);
+}

contrib/spi/refint.source

+DROP FUNCTION check_primary_key ();
+DROP FUNCTION check_foreign_key ();
+
+CREATE FUNCTION check_primary_key ()
+	RETURNS opaque
+	AS '_OBJWD_/refint_DLSUFFIX_'
+	LANGUAGE 'c'
+;
+
+CREATE FUNCTION check_foreign_key ()
+	RETURNS opaque
+	AS '_OBJWD_/refint_DLSUFFIX_'
+	LANGUAGE 'c'
+;