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).
--- /dev/null
+/*
+ * 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);
+}
--- /dev/null
+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';
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