General trigger functions for time-travel

contrib/spi/Makefile

@@ -9,12 +9,11 @@ ifdef REFINT_VERBOSE
 CFLAGS+= -DREFINT_VERBOSE
 endif
 
-TARGETS= refint$(DLSUFFIX) refint.sql
+TARGETS= refint$(DLSUFFIX) refint.sql timetravel$(DLSUFFIX) timetravel.sql
 
 CLEANFILES+= $(TARGETS)
 
 all:: $(TARGETS)
-	rm -f *.obj *.pic
 
 %.sql: %.source
 	rm -f $@; \
@@ -23,4 +22,4 @@ all:: $(TARGETS)
 	    -e "s:_DLSUFFIX_:$(DLSUFFIX):g" < $< > $@
 
 clean: 
-	rm -f $(TARGETS) *.[op]*
+	rm -f $(TARGETS)

contrib/spi/README

@@ -28,10 +28,77 @@ being deleted to null), triggered table column names which correspond
 to primary/unique key, referencing table name and column names corresponding
 to foreign key (, ... - as many referencing tables/keys as specified
 by first argument).
-   Note, that NOT NULL constraint and unique index have to be defined
-by youself.
+   Note, that NOT NULL constraint and unique index have to be defined by
+youself.
 
-   There are examples in refint.example and regression tests 
+   There are examples in refint.example and regression tests
 (sql/triggers.sql).
 
+   To CREATE FUNCTIONs use refint.sql (will be made by gmake from
+refint.source).
 
+
+2. timetravel.c - functions for implementing time travel feature.
+
+   Old internally supported time-travel (TT) used insert/delete
+transaction commit times. To get the same feature using triggers
+you are to add to a table two columns of abstime type to store
+date when a tuple was inserted (start_date) and changed/deleted 
+(stop_date):
+
+CREATE TABLE XXX (
+	...		...
+	date_on		abstime default currabstime(),
+	date_off	abstime default 'infinity'
+	...		...
+);
+
+- so, tuples being inserted with NULLs in date_on/date_off will get
+_current_date_ in date_on (name of start_date column in XXX) and INFINITY in
+date_off (name of stop_date column in XXX).
+
+   Tuples with stop_date equal INFINITY are "valid now": when trigger will
+be fired for UPDATE/DELETE of a tuple with stop_date NOT equal INFINITY then
+this tuple will not be changed/deleted!
+
+   If stop_date equal INFINITY then on
+
+UPDATE: only stop_date in tuple being updated will be changed to current
+date and new tuple with new data (coming from SET ... in UPDATE) will be
+inserted. Start_date in this new tuple will be setted to current date and
+stop_date - to INFINITY.
+
+DELETE: new tuple will be inserted with stop_date setted to current date
+(and with the same data in other columns as in tuple being deleted).
+
+   NOTE:
+1. To get tuples "valid now" you are to add _stop_date_ = 'infinity'
+   to WHERE. Internally supported TT allowed to avoid this...
+   Fixed rewriting RULEs could help here...
+   As work arround you may use VIEWs...
+2. You can't change start/stop date columns with UPDATE! 
+   Use set_timetravel (below) if you need in this.
+
+   FUNCTIONs:
+
+timetravel() is general trigger function.
+
+   You are to create trigger BEFORE (!!!) UPDATE OR DELETE using this
+function on a time-traveled table. You are to specify two arguments: name of
+start_date column and name of stop_date column in triggered table.
+
+currabstime() may be used in DEFAULT for start_date column to get
+current date.
+
+set_timetravel() allows you turn time-travel ON/OFF for a table:
+
+   set_timetravel('XXX', 1) will turn TT ON for table XXX (and report
+old status).
+   set_timetravel('XXX', 0) will turn TT OFF for table XXX (-"-).
+
+Turning TT OFF allows you do with a table ALL what you want.
+
+   There is example in timetravel.example.
+
+   To CREATE FUNCTIONs use timetravel.sql (will be made by gmake from
+timetravel.source).

contrib/spi/timetravel.c

+/*
+ * timetravel.c --	function to get time travel feature
+ *		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 () */
+
+#define ABSTIMEOID	702			/* it should be in pg_type.h */
+
+AbsoluteTime	currabstime(void);
+HeapTuple		timetravel(void);
+int32			set_timetravel(Name relname, int32 on);
+
+typedef struct
+{
+	char   *ident;
+	void   *splan;
+} EPlan;
+
+static EPlan *Plans = NULL;		/* for UPDATE/DELETE */
+static int	nPlans = 0;
+
+static char	  **TTOff = NULL;
+static int		nTTOff = 0;
+
+static EPlan *find_plan(char *ident, EPlan ** eplan, int *nplans);
+
+/*
+ * timetravel () -- 
+ *		1.	IF an update affects tuple with stop_date eq INFINITY 
+ * 			then form (and return) new tuple with stop_date eq current date 
+ * 			and all other column values as in old tuple, and insert tuple 
+ * 			with new data and start_date eq current date and 
+ * 			stop_date eq INFINITY
+ * 			ELSE - skip updation of tuple.
+ * 		2.	IF an delete affects tuple with stop_date eq INFINITY
+ * 			then insert the same tuple with stop_date eq current date
+ * 			ELSE - skip deletion of tuple.
+ * 
+ * In CREATE TRIGGER you are to specify start_date and stop_date column
+ * names:
+ * EXECUTE PROCEDURE
+ * timetravel ('date_on', 'date_off').
+ */
+
+HeapTuple						/* have to return HeapTuple to Executor */
+timetravel()
+{
+	Trigger    *trigger;		/* to get trigger name */
+	char	  **args;			/* arguments */
+	int			attnum[2];		/* fnumbers of start/stop columns */
+	Datum		oldon, oldoff;
+	Datum		newon, newoff;
+	Datum	   *cvals;			/* column values */
+	char	   *cnulls;			/* column nulls */
+	char	   *relname;		/* triggered relation name */
+	Relation	rel;			/* triggered relation */
+	HeapTuple	trigtuple;
+	HeapTuple	newtuple = NULL;
+	HeapTuple	rettuple;
+	TupleDesc	tupdesc;		/* tuple description */
+	int			natts;			/* # of attributes */
+	EPlan	   *plan;			/* prepared plan */
+	char		ident[2 * NAMEDATALEN];
+	bool		isnull;			/* to know is some column NULL or not */
+	int			ret;
+	int			i;
+
+	/*
+	 * Some checks first...
+	 */
+
+	/* Called by trigger manager ? */
+	if (!CurrentTriggerData)
+		elog(WARN, "timetravel: triggers are not initialized");
+	
+	/* Should be called for ROW trigger */
+	if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
+		elog(WARN, "timetravel: can't process STATEMENT events");
+	
+	/* Should be called BEFORE */
+	if (TRIGGER_FIRED_AFTER(CurrentTriggerData->tg_event))
+		elog(WARN, "timetravel: must be fired before event");
+
+	/* INSERT ? */
+	if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
+		elog (WARN, "timetravel: can't process INSERT event");
+	
+	if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
+		newtuple = CurrentTriggerData->tg_newtuple;
+	
+	trigtuple = CurrentTriggerData->tg_trigtuple;
+	
+	rel = CurrentTriggerData->tg_relation;
+	relname = SPI_getrelname(rel);
+	
+	/* check if TT is OFF for this relation */
+	for (i = 0; i < nTTOff; i++)
+		if (strcasecmp (TTOff[i], relname) == 0)
+			break;
+	if (i < nTTOff)				/* OFF - nothing to do */
+	{
+		pfree (relname);
+		return ((newtuple != NULL) ? newtuple : trigtuple);
+	}
+	
+	trigger = CurrentTriggerData->tg_trigger;
+
+	if (trigger->tgnargs != 2)
+		elog(WARN, "timetravel (%s): invalid (!= 2) number of arguments %d", 
+				relname, trigger->tgnargs);
+	
+	args = trigger->tgargs;
+	tupdesc = rel->rd_att;
+	natts = tupdesc->natts;
+	
+	/*
+	 * 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;
+	
+	for (i = 0; i < 2; i++ )
+	{
+		attnum[i] = SPI_fnumber (tupdesc, args[i]);
+		if ( attnum[i] < 0 )
+			elog(WARN, "timetravel (%s): there is no attribute %s", relname, args[i]);
+		if (SPI_gettypeid (tupdesc, attnum[i]) != ABSTIMEOID)
+			elog(WARN, "timetravel (%s): attributes %s and %s must be of abstime type", 
+					relname, args[0], args[1]);
+	}
+	
+	oldon = SPI_getbinval (trigtuple, tupdesc, attnum[0], &isnull);
+	if (isnull)
+		elog(WARN, "timetravel (%s): %s must be NOT NULL", relname, args[0]);
+	
+	oldoff = SPI_getbinval (trigtuple, tupdesc, attnum[1], &isnull);
+	if (isnull)
+		elog(WARN, "timetravel (%s): %s must be NOT NULL", relname, args[1]);
+	
+	/*
+	 * If DELETE/UPDATE of tuple with stop_date neq INFINITY
+	 * then say upper Executor to skip operation for this tuple
+	 */
+	if (newtuple != NULL)						/* UPDATE */
+	{
+		newon = SPI_getbinval (newtuple, tupdesc, attnum[0], &isnull);
+		if (isnull)
+			elog(WARN, "timetravel (%s): %s must be NOT NULL", relname, args[0]);
+		newoff = SPI_getbinval (newtuple, tupdesc, attnum[1], &isnull);
+		if (isnull)
+			elog(WARN, "timetravel (%s): %s must be NOT NULL", relname, args[1]);
+		
+		if ( oldon != newon || oldoff != newoff )
+			elog (WARN, "timetravel (%s): you can't change %s and/or %s columns (use set_timetravel)",
+					relname, args[0], args[1]);
+		
+		if ( newoff != NOEND_ABSTIME )
+		{
+			pfree (relname);	/* allocated in upper executor context */
+			return (NULL);
+		}
+	}
+	else if (oldoff != NOEND_ABSTIME)		/* DELETE */
+	{
+		pfree (relname);
+		return (NULL);
+	}
+	
+	newoff = GetCurrentAbsoluteTime ();
+	
+	/* Connect to SPI manager */
+	if ((ret = SPI_connect()) < 0)
+		elog(WARN, "timetravel (%s): SPI_connect returned %d", relname, ret);
+	
+	/* Fetch tuple values and nulls */
+	cvals = (Datum *) palloc (natts * sizeof (Datum));
+	cnulls = (char *) palloc (natts * sizeof (char));
+	for (i = 0; i < natts; i++)
+	{
+		cvals[i] = SPI_getbinval ((newtuple != NULL) ? newtuple : trigtuple, 
+								  tupdesc, i + 1, &isnull);
+		cnulls[i] = (isnull) ? 'n' : ' ';
+	}
+	
+	/* change date column(s) */
+	if (newtuple)					/* UPDATE */
+	{
+		cvals[attnum[0] - 1] = newoff;			/* start_date eq current date */
+		cnulls[attnum[0] - 1] = ' ';
+		cvals[attnum[1] - 1] = NOEND_ABSTIME;	/* stop_date eq INFINITY */
+		cnulls[attnum[1] - 1] = ' ';
+	}
+	else							/* DELETE */
+	{
+		cvals[attnum[1] - 1] = newoff;			/* stop_date eq current date */
+		cnulls[attnum[1] - 1] = ' ';
+	}
+	
+	/*
+	 * 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, &Plans, &nPlans);
+	
+	/* if there is no plan ... */
+	if (plan->splan == NULL)
+	{
+		void	   *pplan;
+		Oid		   *ctypes;
+		char		sql[8192];
+		
+		/* allocate ctypes for preparation */
+		ctypes = (Oid *) palloc(natts * sizeof(Oid));
+		
+		/*
+		 * Construct query: 
+		 * 	INSERT INTO _relation_ VALUES ($1, ...)
+		 */
+		sprintf(sql, "INSERT INTO %s VALUES (", relname);
+		for (i = 1; i <= natts; i++)
+		{
+			sprintf(sql + strlen(sql), "$%d%s",
+				i, (i < natts) ? ", " : ")");
+			ctypes[i - 1] = SPI_gettypeid(tupdesc, i);
+		}
+		
+		/* Prepare plan for query */
+		pplan = SPI_prepare(sql, natts, ctypes);
+		if (pplan == NULL)
+			elog(WARN, "timetravel (%s): SPI_prepare returned %d", relname, 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, "timetravel (%s): SPI_saveplan returned %d", relname, SPI_result);
+		
+		plan->splan = pplan;
+	}
+	
+	/*
+	 * Ok, execute prepared plan.
+	 */
+	ret = SPI_execp(plan->splan, cvals, cnulls, 0);
+	
+	if (ret < 0)
+		elog(WARN, "timetravel (%s): SPI_execp returned %d", relname, ret);
+	
+	/* Tuple to return to upper Executor ... */
+	if (newtuple)									/* UPDATE */
+	{
+		HeapTuple	tmptuple;
+		
+		tmptuple = SPI_copytuple (trigtuple);
+		rettuple = SPI_modifytuple (rel, tmptuple, 1, &(attnum[1]), &newoff, NULL);
+		/*
+		 * SPI_copytuple allocates tmptuple in upper executor context -
+		 * have to free allocation using SPI_pfree
+		 */
+		SPI_pfree (tmptuple);
+	}
+	else											/* DELETE */
+		rettuple = trigtuple;
+	
+	SPI_finish();		/* don't forget say Bye to SPI mgr */
+	
+	pfree (relname);
+
+	return (rettuple);
+}
+
+/*
+ * set_timetravel () --
+ * 					turn timetravel for specified relation ON/OFF
+ */
+int32
+set_timetravel(Name relname, int32 on)
+{
+	char   *rname;
+	char   *d;
+	char   *s;
+	int		i;
+	
+	for (i = 0; i < nTTOff; i++)
+		if (namestrcmp (relname, TTOff[i]) == 0)
+			break;
+	
+	if (i < nTTOff)				/* OFF currently */
+	{
+		if (on == 0)
+			return (0);
+		
+		/* turn ON */
+		free (TTOff[i]);
+		if (nTTOff == 1)
+			free (TTOff);
+		else
+		{
+			if (i < nTTOff - 1)
+				memcpy (&(TTOff[i]), &(TTOff[i + 1]), (nTTOff - i) * sizeof (char*));
+			TTOff = realloc (TTOff, (nTTOff - 1) * sizeof (char*));
+		}
+		nTTOff--;
+		return (0);
+	}
+	
+	/* ON currently */
+	if (on != 0)
+		return (1);
+	
+	/* turn OFF */
+	if (nTTOff == 0)
+		TTOff = malloc (sizeof (char*));
+	else
+		TTOff = realloc (TTOff, (nTTOff + 1) * sizeof (char*));
+	s = rname = nameout (relname);
+	d = TTOff[nTTOff] = malloc (strlen (rname) + 1);
+	while (*s)
+		*d++ = tolower (*s++);
+	*d = 0;
+	pfree (rname);
+	nTTOff++;
+	
+	return (1);
+
+}
+
+AbsoluteTime
+currabstime ()
+{
+	return (GetCurrentAbsoluteTime ());
+}
+
+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->splan = NULL;
+	(*nplans)++;
+
+	return (newp);
+}

contrib/spi/timetravel.example

+drop table tttest;
+create table tttest (
+	price_id	int4, 
+	price_val	int4, 
+	price_on	abstime default currabstime(),
+	price_off	abstime default 'infinity'
+);
+
+insert into tttest values (1, 1, null, null);
+insert into tttest values (2, 2, null, null);
+insert into tttest values (3, 3, null, null);
+
+create trigger timetravel 
+	before delete or update on tttest
+	for each row 
+	execute procedure 
+	timetravel (price_on, price_off);
+
+select * from tttest;
+delete from tttest where price_id = 2;
+select * from tttest;
+-- what do we see ?
+
+-- get current prices
+select * from tttest where price_off = 'infinity';
+
+-- change price for price_id == 3
+update tttest set price_val = 30 where price_id = 3;
+select * from tttest;
+
+-- now we want to change price_id from 3 to 5 in ALL tuples
+-- but this gets us not what we need
+update tttest set price_id = 5 where price_id = 3;
+select * from tttest;
+
+-- restore data as before last update:
+select set_timetravel('tttest', 0);	-- turn TT OFF!
+delete from tttest where price_id = 5;
+update tttest set price_off = 'infinity' where price_val = 30;
+select * from tttest;
+
+-- and try change price_id now!
+update tttest set price_id = 5 where price_id = 3;
+select * from tttest;
+-- isn't it what we need ?
+
+select set_timetravel('tttest', 1);	-- turn TT ON!
+
+-- we want to correct some date
+update tttest set price_on = 'Jan-01-1990 00:00:01' where price_id = 5 and 
+	price_off <> 'infinity';
+-- but this doesn't work
+
+-- try in this way
+select set_timetravel('tttest', 0);	-- turn TT OFF!
+update tttest set price_on = '01-Jan-1990 00:00:01' where price_id = 5 and 
+	price_off <> 'infinity';
+select * from tttest;
+-- isn't it what we need ?
+
+-- get price for price_id == 5 as it was '10-Jan-1990'
+select * from tttest where price_id = 5 and 
+	price_on <= '10-Jan-1990' and price_off > '10-Jan-1990';

contrib/spi/timetravel.source

+DROP FUNCTION currabstime();
+DROP FUNCTION timetravel();
+DROP FUNCTION set_timetravel(name, int4);
+
+CREATE FUNCTION currabstime() 
+	RETURNS abstime 
+	AS '_OBJWD_/timetravel_DLSUFFIX_'
+	LANGUAGE 'c';
+
+CREATE FUNCTION timetravel() 
+	RETURNS opaque 
+	AS '_OBJWD_/timetravel_DLSUFFIX_'
+	LANGUAGE 'c';
+
+CREATE FUNCTION set_timetravel(name, int4) 
+	RETURNS int4 
+	AS '_OBJWD_/timetravel_DLSUFFIX_'
+	LANGUAGE 'c';