Re: Limit GIST_MAX_SPLIT_PAGES to XLR_MAX_BLOCK_ID - Mailing list pgsql-hackers

From Gurjeet Singh
Subject Re: Limit GIST_MAX_SPLIT_PAGES to XLR_MAX_BLOCK_ID
Date
Msg-id CABwTF4Wdpy69jGiAHQcoUD+dm+agj6oZ-ZM3Dw8Qf9G3VJ6_2w@mail.gmail.com
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In response to Limit GIST_MAX_SPLIT_PAGES to XLR_MAX_BLOCK_ID  (Gurjeet Singh <gurjeet@singh.im>)
List pgsql-hackers
(adding Heikki, since that macro was touched by his commit 04e298b8)

Does my previous description of the problem make sense, or am I fretting over something that's a non-issue.

Best regards,


On Sun, Sep 20, 2015 at 7:03 PM, Gurjeet Singh <gurjeet@singh.im> wrote:
Gin code respects the XLR_MAX_BLOCK_ID when calling XLogEnsureRecordSpace(). But it appears that the Gist code does not try to limit its block-id consumption to XLR_MAX_BLOCK_ID.

The GIST_MAX_SPLIT_PAGES is hard-coded at 75, but XLogEnsureRecordSpace() would reject a request of more than 32 (XLR_MAX_BLOCK_ID).

The attached patch redefines GIST_MAX_SPLIT_PAGES so that in case of a split, gistplacetopage() now throws an error when the block-ids needed exceed 32.

I have used Min(75, XLR_MAX_BLOCK_ID) as the macro expansion, but I believe it can be set to plain XLR_MAX_BLOCK_ID.


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