Re^2: DBI::Sybase -retrieving BLOB values from ms-sql question

That's what I was thinking too but looking at the docs for DBD::Sybase:

Note that LongReadLen has no effect when using DBD::Sybase with an MS-SQL server.

And further on:

Sybase defaults the TEXTSIZE attribute (aka LongReadLen) to 32k, but MS-SQL 7 doesn't seem to do that correctly, resulting in very large memory requests when querying tables with TEXT/IMAGE data columns. The work-around is to set TEXTSIZE to some decent value via $dbh->{LongReadLen} (if that works - I haven't had any confirmation that it does) or via $dbh->do("set textsize <somesize>");

So I think the $dbh->do( "set textsize <somesize>" ) may be your only option -- but luckily mpeppler is a monk and he'll probably be along soon enough with a better answer.

-derby

Comment on Re^2: DBI::Sybase -retrieving BLOB values from ms-sql question

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Re^3: DBI::Sybase -retrieving BLOB values from ms-sql question by mpeppler (Vicar) on Jul 07, 2006 at 15:44 UTC
You are correct - the OP needs to call $dbh->do("set textsize somevalue"); to get things to work. The reason for this is that when $dbh->{longReadLen} is updated DBD::Sybase calls a Sybase API call under the cover, and this API call is not one that is compatible between MS-SQL and Sybase. Michael	[reply]
Re^4: DBI::Sybase -retrieving BLOB values from ms-sql question by anexiole (Novice) on Jul 07, 2006 at 22:48 UTC
i've just found this online String Data Handling (from http://search.cpan.org/~mewp/DBD-Sybase/d +bd-sybase.pod) DBD::Sybase supports CHAR/VARCHAR/BINARY/VARBINARY, limited to 255 cha +racters in length up to version 12.0x. As of 12.5 these datatypes can + be up to 16K in size - but supporting the larger sizes requires that + Open Client 12.5 or later be used. Note that the CHAR type is fixed +length (blank padded). Sybase automatically converts CHAR and VARCHAR data between the charac +ter set of the server (see the syscharset system table) and the chara +cter set of the client, defined by the locale setting of the client. +The BINARY and VARBINARY types are not converted. UTF-8 is supported. See the OpenClient International Developer's Guide in the Sybase OpenC +lient manuals for more on character set issues. Strings can be concatenated using the + SQL operator. [download] it sort of implies that the limitation is stuck at fetching a max of 255 character per blob. Am I wrong(i hope so)? Edit: pre tags replaced with code tags	[reply] [d/l]
Re^5: DBI::Sybase -retrieving BLOB values from ms-sql question by mpeppler (Vicar) on Jul 08, 2006 at 06:01 UTC
The limitation that is referred to here is for char/varchar data, not for blobs. DBD::Sybase has always supported the full blob size (2GB) either via the longReadLen attribute, or via the "set textsize" T-SQL command. Also note that the documentation that you are referring to is primarily aimed at DBD::Sybase built with the Sybase OpenClient libraries. You are using it with FreeTDS, which means that some of the behavior is different, and you should refer to the FreeTDS documentation for additional information. Michael	[reply]
Re^4: DBI::Sybase -retrieving BLOB values from ms-sql question by Anonymous Monk on Jul 10, 2006 at 02:20 UTC
hello michael i have tried using $source_dbh->do("set textsize 40000"); before the prepare statement and it doesn't work... please help:) thank you. gordon	[reply]
Re^5: DBI::Sybase -retrieving BLOB values from ms-sql question by mpeppler (Vicar) on Jul 11, 2006 at 17:18 UTC
I don't know all that much about the issues with DBD::Sybase & MS-SQL, but I can try to help. The most likely problem is that you are for some reason opening more than one connection. This can happen if DBD::Sybase thinks that the connection is still active when prepare() is called. You can set the syb_no_child_con connection attribute to TRUE and this will inhibit multiple connections for simultaneous statement handles. You can also enable the DBI->trace() to see what really happens under the covers. Michael	[reply]
Re^3: DBI::Sybase -retrieving BLOB values from ms-sql question by imp (Priest) on Jul 07, 2006 at 14:13 UTC
Good catch. It's been a little while since I used DBD::Sybase, as I switched over to DBD::ODBC after discovering iodbc Depending on the platform the textsize can be controlled by external configuration as well, e.g. freetds has a 'textsize' setting	[reply]
Re^4: DBI::Sybase -retrieving BLOB values from ms-sql question by anexiole (Novice) on Jul 07, 2006 at 22:44 UTC
hi there whereabts do you set the 'textsize' for freetds?	[reply]
Re^5: DBI::Sybase -retrieving BLOB values from ms-sql question by mpeppler (Vicar) on Jul 08, 2006 at 06:04 UTC
I think it's in the freetds.conf file - you should check the FreeTDS documentation for more information (or ask on the FreeTDS mailing list). Michael	[reply]


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