Re: inserting, index and no index - speed
От | zilch@home.se |
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Тема | Re: inserting, index and no index - speed |
Дата | |
Msg-id | 20010610201505.A29146@loony обсуждение исходный текст |
Ответ на | Re: inserting, index and no index - speed (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: inserting, index and no index - speed
Re: inserting, index and no index - speed |
Список | pgsql-general |
The test script that set up the tables is the following: --- /* Cleanup */ DROP SEQUENCE index_with_id_seq; DROP SEQUENCE index_without_id_seq; DROP INDEX name_index; DROP TABLE index_with; DROP TABLE index_without; /* Create a table with an index */ CREATE TABLE index_with ( id SERIAL, name TEXT ); CREATE INDEX name_index ON index_with(name); /* Create a table without an index */ CREATE TABLE index_without ( id SERIAL, name TEXT ); --- This is run just before it is tested, then I have this little C++ program that inserts N rows into the tables, and meassures how long it takes. A DELETE * FROM table (both tables) followed by a VACCUUM is also run before each test run (which consists of regular INSERT statements). Do I do anything wrong? The postmaster (7.1.2) is run with then current Debian testing/unstable standard options. Daniel Akerud > > I just noticed that inserting 10000 tuples in an indexed table took exactly > > the same amount of time as inserting 10000 tuples in a non-indexed table > > (194 seconds). Why is this? The difference in MySQL is about 50% longer in > > an indexed table. > > Surprises me too. Which PG version, and what are the test conditions > exactly? (Table and index declarations; is table empty initially; > how is backend being driven, and what commands are issued exactly? > How many shared buffers, platform, etc) > > Under PG 7.1, it's possible that your test caused no actual I/O except > to the WAL log ... but I'd still think that the volume of WAL I/O > would be greater when writing an index. > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org >
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