Re: bytea
От | Steve Crawford |
---|---|
Тема | Re: bytea |
Дата | |
Msg-id | 20030207185431.BB737103F7@polaris.pinpointresearch.com обсуждение исходный текст |
Ответ на | Re: bytea ("Adrian Chong" <achong@cecid.hku.hk>) |
Список | pgsql-sql |
That would be convenient but there are some difficulties. Say you have a function that worked something like: insert.....values (...., filetobytea("/home/me/myfile"),...); It would be a nice ability to have but the server may not be on the same machine (or even the same type/os/filesystem) as the client so sending a pathname to the server is of little use. Such an ability must be handled by the client which can read/translate the local file into the appropriate byte sequence to send to the server. I'm toying with a client program in C program that would include the ability to take a file on the client machine and store it in a bytea field but haven't come up with a good way to handle the necessary buffer space (ie. I don't see any way to "stream" data to the server - it appears I need to allocate sufficient buffer space for the entire file plus the entire escaped version of the file before I can generate the query which causes me some other problems.) Any suggestions would be appreciated. Cheers, Steve On Wednesday 05 February 2003 2:25 am, Adrian Chong wrote: > Hi Christoph, > > Thanks for your reply. But what I want to do is loading a file of a > particular path with a sql statement in psql. Why I need to care about how > the file looks like? Thanks. > > Adrian > > ----- Original Message ----- > From: "Christoph Haller" <ch@rodos.fzk.de> > To: <pgsql-sql@postgresql.org> > Cc: <achong@cecid.hku.hk> > Sent: Wednesday, February 05, 2003 6:15 PM > Subject: Re: [SQL] bytea > > > > I have a table containing a field of type bytea: > > > > > > CREATE TABLE a_table ( > > > a_field bytea > > > ); > > > > > > How can I import a file in a SQL script? What function I can use? > > > > The documentation says as in PostgreSQL 7.2.1 (I doubt this changed > > significantly since) > > > > Octets of certain values must be escaped (but all octet values may be > > escaped) when used as part of a string literal in an SQL > > statement. In general, to escape an octet, it is converted into the > > three-digit octal number equivalent of its decimal octet value, and > > preceded by two backslashes. > > > > In general it goes like this > > INSERT INTO a_table ( a_field ) VALUES ( '\\000\\001\\002\\003' ) ; > > to load the first four ASCII characters. > > You did not mention how your file looks like. > > There is also a C function available called PQescapeBytea > > which does all the required escaping to store memory areas in bytea > > columns. > > Refer to Command Execution Functions within libpq - C Library for > > details. > > > > Regards, Christoph > > > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 3: if posting/reading through Usenet, please send an appropriate > > subscribe-nomail command to majordomo@postgresql.org so that your > > message can get through to the mailing list cleanly > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Don't 'kill -9' the postmaster
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