64 lines
1.8 KiB
Plaintext
64 lines
1.8 KiB
Plaintext
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drop table tttest;
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create table tttest (
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price_id int4,
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price_val int4,
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price_on abstime default currabstime(),
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price_off abstime default 'infinity'
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);
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insert into tttest values (1, 1, null, null);
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insert into tttest values (2, 2, null, null);
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insert into tttest values (3, 3, null, null);
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create trigger timetravel
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before delete or update on tttest
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for each row
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execute procedure
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timetravel (price_on, price_off);
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select * from tttest;
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delete from tttest where price_id = 2;
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select * from tttest;
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-- what do we see ?
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-- get current prices
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select * from tttest where price_off = 'infinity';
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-- change price for price_id == 3
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update tttest set price_val = 30 where price_id = 3;
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select * from tttest;
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-- now we want to change price_id from 3 to 5 in ALL tuples
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-- but this gets us not what we need
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update tttest set price_id = 5 where price_id = 3;
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select * from tttest;
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-- restore data as before last update:
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select set_timetravel('tttest', 0); -- turn TT OFF!
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delete from tttest where price_id = 5;
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update tttest set price_off = 'infinity' where price_val = 30;
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select * from tttest;
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-- and try change price_id now!
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update tttest set price_id = 5 where price_id = 3;
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select * from tttest;
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-- isn't it what we need ?
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select set_timetravel('tttest', 1); -- turn TT ON!
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-- we want to correct some date
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update tttest set price_on = 'Jan-01-1990 00:00:01' where price_id = 5 and
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price_off <> 'infinity';
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-- but this doesn't work
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-- try in this way
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select set_timetravel('tttest', 0); -- turn TT OFF!
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update tttest set price_on = '01-Jan-1990 00:00:01' where price_id = 5 and
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price_off <> 'infinity';
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select * from tttest;
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-- isn't it what we need ?
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-- get price for price_id == 5 as it was '10-Jan-1990'
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select * from tttest where price_id = 5 and
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price_on <= '10-Jan-1990' and price_off > '10-Jan-1990';
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