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524cfad23f
the new timetravel.c,
new timetravel.README (cut from spi/README and modified),
modified timetravel.sql.in
and modified timetravel.example.
Features:
- optionally 3 parameter for insert/update/delete user name
- work with CREATE UNIQUE INDEX ixxx on table xxx
(unique_field,time_off);
(the original version was work with unique index on 6.5.0-6.5.3,
and not work on 7.3.2,7.3.3)
(before 6.5.0 and between 6.5.3 and 7.3.2 I dont know)
- get_timetravel(tablename) function for check timetravel-status.
- timetravel trigger not change oid of the active record. (it is not a
good feature, because the old version is automatice prevent the paralel
update with "where oid=nnn")
B?jthe Zolt?n
117 lines
4.4 KiB
Plaintext
117 lines
4.4 KiB
Plaintext
2. timetravel.c - functions for implementing time travel feature.
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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I rewritten this, because:
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on original version of postgresql 7.3.2-7.3.3:
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the UPDATE not work on timetravel.example if I added
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>create unique index tttest_idx on tttest (price_id,price_off);
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>update tttest set price_val = 30 where price_id = 3;
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ERROR: Cannot insert a duplicate key into unique index tttest_idx
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And UPDATE not work on table tttest after
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>alter table tttest add column q1 text;
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>alter table tttest add column q2 int;
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>alter table tttest drop column q1;
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>update tttest set price_val = 30 where price_id = 3;
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ERROR: Parameter '$5' is out of range
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And I add a new optional feature: my new timetravel have +3 optional parameters:
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inserter_user, updater_user, deleter_user.
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And I add a new function: get_timetravel for get timetravel status
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without change it.
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A big difference:
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the old version on UPDATE changed oid on active ('infinity') record,
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the new version UPDATE keep oid, and the overdued record have a new oid.
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I sign with '!!!' my comment in this file.
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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Old internally supported time-travel (TT) used insert/delete
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transaction commit times. To get the same feature using triggers
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you are to add to a table two columns of abstime type to store
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date when a tuple was inserted (start_date) and changed/deleted
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(stop_date):
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CREATE TABLE XXX (
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... ...
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date_on abstime default currabstime(),
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date_off abstime default 'infinity'
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... ...
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/* !!! and (if have) */
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ins_user text /* user, who insert this record */
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upd_user text /* user, who updated this record */
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del_user text /* user, who deleted this record */
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... ...
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);
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!!! on INSERT my new version:
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... and optionally set ins_user to current user, upd_user and del_user to null.
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- so, tuples being inserted with NULLs in date_on/date_off will get
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_current_date_ in date_on (name of start_date column in XXX) and INFINITY in
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date_off (name of stop_date column in XXX).
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Tuples with stop_date equal INFINITY are "valid now": when trigger will
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be fired for UPDATE/DELETE of a tuple with stop_date NOT equal INFINITY then
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this tuple will not be changed/deleted!
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If stop_date equal INFINITY then on
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UPDATE:
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original version was:
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only stop_date in tuple being updated will be changed to current
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date and new tuple with new data (coming from SET ... in UPDATE) will be
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inserted. Start_date in this new tuple will be setted to current date and
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stop_date - to INFINITY.
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On my new version:
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insert a new tuple with old values, but stop_date changed to current date;
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and update original tuple with new data, and update start_date to current date
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and optionally set upd_user to current user and clear ins_user,del_user.
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DELETE: new tuple will be inserted with stop_date setted to current date
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(and with the same data in other columns as in tuple being deleted).
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On my new version:
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... and optionally set del_user to current user.
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NOTE:
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1. To get tuples "valid now" you are to add _stop_date_ = 'infinity'
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to WHERE. Internally supported TT allowed to avoid this...
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Fixed rewriting RULEs could help here...
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As work arround you may use VIEWs...
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2. You can't change start/stop date columns with UPDATE!
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Use set_timetravel (below) if you need in this.
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FUNCTIONs:
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timetravel() is general trigger function.
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You are to create trigger BEFORE UPDATE OR DELETE using this
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function on a time-traveled table. You are to specify two arguments: name of
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start_date column and name of stop_date column in triggered table.
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Or add +3 arguments:
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name of insert_user column, name of update_user column, name of delete_user column
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currabstime() may be used in DEFAULT for start_date column to get
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current date.
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!!! I deleted this function, because I newer used this.
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set_timetravel() allows you turn time-travel ON/OFF for a table:
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set_timetravel('XXX', 1) will turn TT ON for table XXX (and report
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old status).
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set_timetravel('XXX', 0) will turn TT OFF for table XXX (-"-).
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Turning TT OFF allows you do with a table ALL what you want.
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get_timetravel() reports time-travel status ON(1)/OFF(0) for a table.
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get_timetravel() and set_timetravel() not checking existing of table and
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existing of timetravel trigger on specified table.
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There is example in timetravel.example.
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To CREATE FUNCTIONs use timetravel.sql (will be made by gmake from
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timetravel.source).
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