answering to myself. :-)
Zoltan Boszormenyi írta:
> I just noticed that psql's unformatted output uses too much
> memory. Is it normal? It seems that psql draws all records
> of a query off the server before it displays or writes the output.
> I would expect this only with formatted output.
> Problem is, I have an export that produces 500'000+ records
> which changes frequently. Several (20+) sites run this query
> nightly with different parameters and download it. The SELECTs
> that run in psql -A -t -c '...' may overlap and the query that runs
> in less than 1.5 minutes if it's the only one at the time may take
> 3+ hours if ten such queries overlap. The time is mostly spent
> in swapping, all psql processes take up 300+ MB, so the 1GB
> server is brought to its knees quickly, peek swap usage is 1.8 GB.
> I watched the progress in top and the postmaster processes finished
> their work in about half an hour (that would still be acceptable)
> then the psql processes started eating up memory as they read
> the records.
> PostgreSQL 8.1.4 was used on RHEL3.
> Is there a way to convince psql to use less memory in unformatted
> mode? I know COPY will be able to use arbitrary SELECTs
> but until then I am still stuck with redirecting psql's output.
The answer it to use SELECT INTO TEMP and then COPY.
Psql will use much less memory that way. But still...
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