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diff --git a/contrib/spi/README b/contrib/spi/README index 65868f0fc7..e69de29bb2 100644 --- a/contrib/spi/README +++ b/contrib/spi/README @@ -1,104 +0,0 @@ - -Here are general trigger functions provided as workable examples -of using SPI and triggers. "General" means that functions may be -used for defining triggers for any tables but you have to specify -table/field names (as described below) while creating a trigger. - -1. refint.c - functions for implementing referential integrity. - -check_primary_key () is to used for foreign keys of a table. - - You are to create trigger (BEFORE INSERT OR UPDATE) using this -function on a table referencing another table. You are to specify -as function arguments: triggered table column names which correspond -to foreign key, referenced table name and column names in referenced -table which correspond to primary/unique key. - You may create as many triggers as you need - one trigger for -one reference. - -check_foreign_key () is to used for primary/unique keys of a table. - - You are to create trigger (BEFORE DELETE OR UPDATE) using this -function on a table referenced by another table(s). You are to specify -as function arguments: number of references for which function has to -performe checking, action if referencing key found ('cascade' - to delete -corresponding foreign key, 'restrict' - to abort transaction if foreign keys -exist, 'setnull' - to set foreign key referencing primary/unique key -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. - - 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). |