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From: Hongxu Ma <[email protected]>
To: David G. Johnston <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: PSQL error: total cell count of XXX exceeded
Date: Sat, 26 Aug 2023 11:19:03 +0000
Message-ID: <TYBP286MB03514675D5D9AA3F533DC987B4E2A@TYBP286MB0351.JPNP286.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <CAKFQuwYfypo7hMXs8a7Ccx4x2bv1XKCMu=pOoQAfq_0Fpu7YQQ@mail.gmail.com>
References: <TYBP286MB0351B057B101C90D7C1239E6B4E2A@TYBP286MB0351.JPNP286.PROD.OUTLOOK.COM>
	<CAKFQuwYfypo7hMXs8a7Ccx4x2bv1XKCMu=pOoQAfq_0Fpu7YQQ@mail.gmail.com>

Thank you David.

From the code logic, I don't think this check is meant to check the limit:
If it enters the double-loop (cont.nrows * cont.ncolumns) in printQuery(), the check should be always false (except overflow happened). So, if want to check the limit, we could have done this check before the double-loop: just checking PGresult and reports error earlier.

> I wouldn’t be adverse to an improved error message, and possibly documenting said limit.

Agreed with you, current error message may even report a negative value, it's very confusing for user. It's better to introduce a limit here. Or using a bigger integer type (e.g. long) for them, but it's also have the theoretical upbound.

Thanks.

________________________________
From: David G. Johnston <[email protected]>
Sent: Saturday, August 26, 2023 12:09
To: Hongxu Ma <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: PSQL error: total cell count of XXX exceeded

On Friday, August 25, 2023, Hongxu Ma <[email protected]<mailto:[email protected]>> wrote:

When I tried to select a big amount of rows, psql complains a error "Cannot add cell to table content: total cell count of 905032704 exceeded."

 We should use long for ncolumns and nrows and give a more obvious error message here.

Any thoughts? or some other hidden reasons?

9 millions cells seems more than realistic a limit for a psql query result output.  In any case it isn’t a bug, the code demonstrates that fact by producing an explicit error.

I wouldn’t be adverse to an improved error message, and possibly documenting said limit.

David J.

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