README for refint.c and example of using.

This commit is contained in:
Vadim B. Mikheev 1997-09-12 02:41:15 +00:00
parent c853ca05a4
commit f1861395f3
3 changed files with 121 additions and 1 deletions

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@ -14,6 +14,7 @@ TARGETS= refint$(DLSUFFIX) refint.sql
CLEANFILES+= $(TARGETS)
all:: $(TARGETS)
rm -f *.obj *.pic
%.sql: %.source
rm -f $@; \
@ -22,4 +23,4 @@ all:: $(TARGETS)
-e "s:_DLSUFFIX_:$(DLSUFFIX):g" < $< > $@
clean:
rm -f $(TARGETS) refint.o
rm -f $(TARGETS) *.[op]*

37
contrib/spi/README Normal file
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@ -0,0 +1,37 @@
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).

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--Column ID of table A is primary key:
CREATE TABLE A (
ID int4 not null
);
CREATE UNIQUE INDEX AI ON A (ID);
--Columns REFB of table B and REFC of C are foreign keys referenting ID of A:
CREATE TABLE B (
REFB int4
);
CREATE INDEX BI ON B (REFB);
CREATE TABLE C (
REFC int4
);
CREATE INDEX CI ON C (REFC);
--Trigger for table A:
CREATE TRIGGER AT BEFORE DELETE OR UPDATE ON A FOR EACH ROW
EXECUTE PROCEDURE
check_foreign_key (2, 'cascade', 'ID', 'B', 'REFB', 'C', 'REFC');
/*
2 - means that check must be performed for foreign keys of 2 tables.
cascade - defines that corresponding keys must be deleted.
ID - name of primary key column in triggered table (A). You may
use as many columns as you need.
B - name of (first) table with foreign keys.
REFB - name of foreign key column in this table. You may use as many
columns as you need, but number of key columns in referenced
table (A) must be the same.
C - name of second table with foreign keys.
REFC - name of foreign key column in this table.
*/
--Trigger for table B:
CREATE TRIGGER BT BEFORE INSERT OR UPDATE ON B FOR EACH ROW
EXECUTE PROCEDURE
check_primary_key ('REFB', 'A', 'ID');
/*
REFB - name of foreign key column in triggered (B) table. You may use as
many columns as you need, but number of key columns in referenced
table must be the same.
A - referenced table name.
ID - name of primary key column in referenced table.
*/
--Trigger for table C:
CREATE TRIGGER CT BEFORE INSERT OR UPDATE ON C FOR EACH ROW
EXECUTE PROCEDURE
check_primary_key ('REFC', 'A', 'ID');
-- Now try
INSERT INTO A VALUES (10);
INSERT INTO A VALUES (20);
INSERT INTO A VALUES (30);
INSERT INTO A VALUES (40);
INSERT INTO A VALUES (50);
INSERT INTO B VALUES (1); -- invalid reference
INSERT INTO B VALUES (10);
INSERT INTO B VALUES (30);
INSERT INTO B VALUES (30);
INSERT INTO C VALUES (11); -- invalid reference
INSERT INTO C VALUES (20);
INSERT INTO C VALUES (20);
INSERT INTO C VALUES (30);
DELETE FROM A WHERE ID = 10;
DELETE FROM A WHERE ID = 20;
DELETE FROM A WHERE ID = 30;
SELECT * FROM A;
SELECT * FROM B;
SELECT * FROM C;