General trigger functions for time-travel

Author: vadim4o

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).