From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
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To: | Alexander Korotkov <aekorotkov(at)gmail(dot)com> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: WIP: Fast GiST index build |
Date: | 2011-07-13 13:59:39 |
Message-ID: | 4E1DA4CB.9020209@enterprisedb.com |
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Lists: | pgsql-hackers |
On 12.07.2011 11:34, Alexander Korotkov wrote:
> New version of patch with a little more refactoring and comments.
Great! The README helps tremendously to understand this, thanks for that.
One thing that caught my eye is that when you empty a buffer, you load
the entire subtree below that buffer, down to the next buffered or leaf
level, into memory. Every page in that subtree is kept pinned. That is a
problem; in the general case, the buffer manager can only hold a modest
number of pages pinned at a time. Consider that the minimum value for
shared_buffers is just 16. That's unrealistically low for any real
system, but the default is only 32MB, which equals to just 4096 buffers.
A subtree could easily be larger than that.
I don't think you're benefiting at all from the buffering that BufFile
does for you, since you're reading/writing a full block at a time
anyway. You might as well use the file API in fd.c directly, ie.
OpenTemporaryFile/FileRead/FileWrite.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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