Bug #81688 [Com]: PDO_ODBC doesn't handle fixed-length character columns with character conversio

From: Date: Wed, 23 Nov 2022 05:04:28 +0000
Subject: Bug #81688 [Com]: PDO_ODBC doesn't handle fixed-length character columns with character conversio
References: 1  Groups: php.bugs 
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Edit report at https://bugs.php.net/bug.php?id=81688&edit=1

 ID:                 81688
 Comment by:         ari5262 at gmail dot com
 Reported by:        calvin at cmpct dot info
 Summary:            PDO_ODBC doesn't handle fixed-length character
                     columns with character conversio
 Status:             Assigned
 Type:               Bug
 Package:            PDO ODBC
 Operating System:   IBM i 7.2
 PHP Version:        8.0.13
 Assigned To:        cmb
 Block user comment: N
 Private report:     N

 New Comment:

I am also getting the same issue mentioned above.

<https://www.jcpenneykiosk.review/>/php.net


Previous Comments:
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[2022-06-21 13:27:28] cmb@php.net

Thanks for the update, and the reminder! :)

I shall have a look at this tomorrow.

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[2022-06-20 17:43:36] calvin at cmpct dot info

FWIW, as an update:

IBM released a new version of the Db2i driver that's worked around the issue for us by
reporting the size after conversion. However, the underlying bug in PDO_ODBC/odbc is still lurking
and could affect other drivers, so it's still worth pursuing a fix for it.

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[2022-01-26 20:56:02] calvin at cmpct dot info

Nitpick I have found that probably doesn't matter: odbc_result_all doesn't work with the
patch, it seems. It's deprecated, so I assume it's not a big deal, but it's something
I noticed debugging some unrelated code.

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[2022-01-20 19:11:37] calvin at cmpct dot info

Brief update w/ the PDO_ODBC patch from last week: The user does report the patch works for them
without any (noticeable) performance regression. Probably a bit rough still, but good to know so
far.

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[2022-01-14 16:49:39] cmb@php.net

> So, I've ported the logic over for PDO_ODBC and I have the patch
> here: […]

Ah, cool!  It might be possible to simplify further by just
setting S->going_long = 1 early (but that doesn't matter for now).

> coercing to string, have to get assembled in a 256 byte buffer
> piecemeal

I think that code is indeed rather suboptimal.  I still wonder why
fetching in small chunks is claimed to be faster than reading a
single chunk[1].

> PDO_ODBC is *noticeably* faster at least on Linux.

That's interesting!  Might be worth investigating.

[1] <https://github.com/php/php-src/pull/6716#issuecomment-783461335>

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