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Clean up the messy semantics (not to mention inefficiency) of PageGetTempPage

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by splitting it into three functions with better-defined behaviors.

Zdenek Kotala
This commit is contained in:
Tom Lane
2008-11-03 20:47:49 +00:00
parent f0dae70431
commit b4eae023bb
10 changed files with 60 additions and 55 deletions
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53
src/backend/storage/page/bufpage.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.80 2008/07/13 21:50:04 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.81 2008/11/03 20:47:48 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -254,28 +254,59 @@ PageAddItem(Page page,
/*
* PageGetTempPage
* Get a temporary page in local memory for special processing
* Get a temporary page in local memory for special processing.
* The returned page is not initialized at all; caller must do that.
*/
Page
PageGetTempPage(Page page, Size specialSize)
PageGetTempPage(Page page)
{
Size pageSize;
Page temp;
pageSize = PageGetPageSize(page);
temp = (Page) palloc(pageSize);
return temp;
}
/*
* PageGetTempPageCopy
* Get a temporary page in local memory for special processing.
* The page is initialized by copying the contents of the given page.
*/
Page
PageGetTempPageCopy(Page page)
{
Size pageSize;
Page temp;
PageHeader thdr;
pageSize = PageGetPageSize(page);
temp = (Page) palloc(pageSize);
thdr = (PageHeader) temp;
/* copy old page in */
memcpy(temp, page, pageSize);
/* set high, low water marks */
thdr->pd_lower = SizeOfPageHeaderData;
thdr->pd_upper = pageSize - MAXALIGN(specialSize);
return temp;
}
/* clear out the middle */
MemSet((char *) temp + thdr->pd_lower, 0, thdr->pd_upper - thdr->pd_lower);
/*
* PageGetTempPageCopySpecial
* Get a temporary page in local memory for special processing.
* The page is PageInit'd with the same special-space size as the
* given page, and the special space is copied from the given page.
*/
Page
PageGetTempPageCopySpecial(Page page)
{
Size pageSize;
Page temp;
pageSize = PageGetPageSize(page);
temp = (Page) palloc(pageSize);
PageInit(temp, pageSize, PageGetSpecialSize(page));
memcpy(PageGetSpecialPointer(temp),
PageGetSpecialPointer(page),
PageGetSpecialSize(page));
return temp;
}