Re: [HACKERS] text should be a blob field
От | Peter T Mount |
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Тема | Re: [HACKERS] text should be a blob field |
Дата | |
Msg-id | Pine.LNX.3.95.980303195117.25913C-100000@maidast обсуждение исходный текст |
Ответ на | Re: [HACKERS] text should be a blob field (Bruce Momjian <maillist@candle.pha.pa.us>) |
Ответы |
Re: [QUESTIONS] Re: [HACKERS] text should be a blob field
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Список | pgsql-hackers |
On Tue, 3 Mar 1998, Bruce Momjian wrote: > > make text a blob datatype (maybe storing <= 8k row with tuple, >=8k in blob > > tablespace) > > Hmmm. > There was some talk about this about a month ago. Although we now have blob support in the JDBC driver, there is one outstanding issue with them, that I was waiting for 6.3 to be released before starting on it (and almost certainly starting a discussion here about it). Allowing text to use blobs for values larger than the current block size would hit the same problem. Ok, here's what the problem is at the moment: The JDBC example ImageViewer uses a table to store the name of an image, and the OID of the associated blob. # create table images (imgname name,imgoid oid); Ok, we now create an entry in the table for an image with: # insert into images values ('test.gif',lo_import('/home/pmount/test.gif')); This is fine so far. Now say we delete that row with: # delete from images where name = 'test.gif'; Fine again, except that the blob is still in the database. To get round this, you would have to add extra statements to handle this, and for JDBC, there is no standard way to do this. What I was thinking of, was to create a new type 'blob' which would delete the associated large object when the row is deleted. However, here's the problems against this: 1. Is there a call made by the backend to each datatype when a row is deleted? I can't see one. 2. When we update a row, we don't want the overhead of copying a very large blob when a row is first copied, then the original deleted, etc. Anyhow, I'm thinking of various ways around this - just don't hold your breath ;-) -- Peter T Mount petermount@earthling.net or pmount@maidast.demon.co.uk Main Homepage: http://www.demon.co.uk/finder Work Homepage: http://www.maidstone.gov.uk Work EMail: peter@maidstone.gov.uk
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