Fetching multiple rows in single round trip
От | Jon Smark |
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Тема | Fetching multiple rows in single round trip |
Дата | |
Msg-id | 1337363188.90482.YahooMailNeo@web112806.mail.gq1.yahoo.com обсуждение исходный текст |
Ответы |
Re: Fetching multiple rows in single round trip
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Список | pgsql-general |
Dear postgresql-general, What would be the best way to fetch in a single round trip a set of table rows? To clarify, suppose I have a 'widgets' table with columns 'wid' and 'data', and I wish to retrieve all rows that belong to the client side array $targets. Obviously one solution would be to loop on the client-side, with each iteration fetching one row. This however entails many round trips in the client <-> postmaster communication, which is undesirable for performance reasons. Therefore, I would rather tell the PostgreSQL server to give me all rows whose wid belongs in a given set. I can think of two solutions: 1) "SELECT wid, data FROM widgets WHERE wid IN $targets" 2) "SELECT wid, data FROM widgets WHERE ARRAY [wid] <@ $targets" Is there another (better) approach I'm missing? Also, is there any significant performance difference for PostgreSQL between solutions 1 and 2? (Solution 1 seems more efficient, though solution 2 is actually a better fit for the client-side bindings I'm using). Thanks in advance! Jon
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