diff options
Diffstat (limited to 'contrib/spi/README')
| -rw-r--r-- | contrib/spi/README | 56 |
1 files changed, 38 insertions, 18 deletions
diff --git a/contrib/spi/README b/contrib/spi/README index 65868f0fc7a..5d332cb585d 100644 --- a/contrib/spi/README +++ b/contrib/spi/README @@ -8,8 +8,8 @@ table/field names (as described below) while creating a trigger. 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 + You have to create trigger (BEFORE INSERT OR UPDATE) using this +function on a table referencing another table. You have 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. @@ -18,8 +18,8 @@ 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 + You have to create trigger (BEFORE DELETE OR UPDATE) using this +function on a table referenced by another table(s). You have 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 @@ -42,20 +42,26 @@ refint.source). 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 +you have 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' + date_on abstime, + date_off abstime ... ... ); -- 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). +CREATE TRIGGER timetravel + BEFORE INSERT OR DELETE OR UPDATE ON tttest + FOR EACH ROW + EXECUTE PROCEDURE + timetravel (date_on, date_off); + + 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 @@ -72,7 +78,7 @@ 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' +1. To get tuples "valid now" you have 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... @@ -83,12 +89,9 @@ DELETE: new tuple will be inserted with stop_date setted to current date 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. + You have to create trigger BEFORE (!!!) INSERT OR UPDATE OR DELETE using +this function on a time-traveled table. You have to specify two arguments: +name of start_date column and name of stop_date column in triggered table. set_timetravel() allows you turn time-travel ON/OFF for a table: @@ -96,9 +99,26 @@ set_timetravel() allows you turn time-travel ON/OFF for a table: 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. +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). + + +3. autoinc.c - function for implementing AUTOINCREMENT/IDENTITY feature. + + You have to create BEFORE INSERT OR UPDATE trigger using function +autoinc(). You have to specify as function arguments: column name +(of int4 type) for which you want to get this feature and name of +SEQUENCE from which next value has to be fetched when NULL or 0 +value is being inserted into column (, ... - you are able to specify +as many column/sequence pairs as you need). + + There is example in autoinc.example. + + To CREATE FUNCTION use autoinc.sql (will be made by gmake from +autoinc.source). + + |