From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Brice André <brice(at)famille-andre(dot)be> |
Cc: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: Memory exhaustion on large query |
Date: | 2021-12-12 18:43:51 |
Message-ID: | 106300.1639334631@sss.pgh.pa.us |
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Lists: | pgsql-sql |
=?UTF-8?B?QnJpY2UgQW5kcsOp?= <brice(at)famille-andre(dot)be> writes:
> The content of the table is so huge that, if PQsendQueryPrepared retrieves
> all data, or if postgresql engine is creating temp file with all data, the
> query cannot succeed (I have no enough RAM or disk space to copy the whole
> data). But I was expecting that using PQsendQueryPrepared and PQgetResult
> would avoid this by returning one result at a time.
You're confusing asynchronous mode with single-row mode. Async mode,
per se, doesn't change memory consumption; it just lets you do something
else while waiting for the query result. You are (I suppose) missing
a call to PQsetSingleRowMode --- see
https://www.postgresql.org/docs/current/libpq-single-row-mode.html
regards, tom lane
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