From: | Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | t-ishii(at)sra(dot)co(dot)jp, Karel Zak - Zakkr <zakkr(at)zf(dot)jcu(dot)cz>, pgsql-hackers <pgsql-hackers(at)postgreSQL(dot)org> |
Subject: | Re: [HACKERS] compression in LO and other fields |
Date: | 1999-11-12 13:42:22 |
Message-ID: | 199911121342.WAA01906@ext04.sra.co.jp |
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Lists: | pgsql-hackers |
> > It sounds ideal but I remember that Vadim said inserting a 2GB record
> > is not good idea since it will be written into the log too. If it's a
> > necessary limitation from the point of view of WAL, we have to accept
> > it, I think.
>
> LO won't make that any better: the data still goes into a table.
> You'd have 2GB worth of WAL entries either way.
What in my mind was LO that is not under the transaction control. I
would not say this is a good thing, but I'm afraid we might need this
kind of beast in WAL.
> The only thing LO would do for you is divide the data into block-sized
> tuples, so there would be a bunch of little WAL entries instead of one
> big one. But that'd probably be easy to duplicate too. If we implement
> big tuples by chaining together disk-block-sized segments, which seems
> like the most likely approach, couldn't WAL log each segment as a
> separate log entry? If so, there's almost no difference between LO and
> inline field for logging purposes.
Right.
BTW, does anybody know how BLOBs are handled by WAL in commercial
DBMSs?
---
Tatsuo Ishii
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