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btree source code cleanups:

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I refactored findsplitloc and checksplitloc so that the division of
labor is more clear IMO. I pushed all the space calculation inside the
loop to checksplitloc.

I also fixed the off by 4 in free space calculation caused by
PageGetFreeSpace subtracting sizeof(ItemIdData), even though it was
harmless, because it was distracting and I felt it might come back to
bite us in the future if we change the page layout or alignments.
There's now a new function PageGetExactFreeSpace that doesn't do the
subtraction.

findsplitloc now tries the "just the new item to right page" split as
well. If people don't like the refactoring, I can write a patch to just
add that.

Heikki Linnakangas
This commit is contained in:
Bruce Momjian
2007-02-21 20:02:17 +00:00
parent 526b1d6979
commit 6f519ad01c
3 changed files with 121 additions and 58 deletions
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26
src/backend/storage/page/bufpage.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.70 2007/01/05 22:19:38 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.71 2007/02/21 20:02:17 momjian Exp $
*
*-------------------------------------------------------------------------
*/
@@ -418,7 +418,8 @@ PageRepairFragmentation(Page page, OffsetNumber *unused)
/*
* PageGetFreeSpace
* Returns the size of the free (allocatable) space on a page.
* Returns the size of the free (allocatable) space on a page,
* deducted by the space needed for a new line pointer.
*/
Size
PageGetFreeSpace(Page page)
@@ -434,7 +435,26 @@ PageGetFreeSpace(Page page)
if (space < (int) sizeof(ItemIdData))
return 0;
space -= sizeof(ItemIdData); /* XXX not always appropriate */
space -= sizeof(ItemIdData);
return (Size) space;
}
/*
* PageGetExactFreeSpace
* Returns the size of the free (allocatable) space on a page.
*/
Size
PageGetExactFreeSpace(Page page)
{
int space;
/*
* Use signed arithmetic here so that we behave sensibly if pd_lower >
* pd_upper.
*/
space = (int) ((PageHeader) page)->pd_upper -
(int) ((PageHeader) page)->pd_lower;
return (Size) space;
}