From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Denis Perchine <dyp(at)perchine(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Caching number of blocks in relation to avoi lseek. |
Date: | 2000-06-12 18:05:45 |
Message-ID: | 200006121805.OAA05626@candle.pha.pa.us |
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Lists: | pgsql-hackers pgsql-patches |
> Hello all,
>
> While digging the code I found out quite interesting comment in
> src/backend/access/heap/hio.c before function RelationPutHeapTupleAtEnd
>
> * Eventually, we should cache the number of blocks in a relation somewhere.
> * Until that time, this code will have to do an lseek to determine the number
> * of blocks in a relation.
>
> As far as I can see there's field rd_nblocks in Relation.
>
> Question: is this field properly updated? Could it be used instead of RelationGetNumberOfBlocks
> which calls lseek.
Probably should be kept up-to-date. Currently only vacuum sets it. It
would have to be kept up-to-date for every INSERT/UPDATE that adds a block.
--
Bruce Momjian | http://www.op.net/~candle
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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