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Preserve the number of requested PAGECACHE pages even if the memory pointer

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or size is zero.  Enhance the pcache1.c header comment to explain the memory
layout of a page cache line.

FossilOrigin-Name: dacb2a615ce1c0573baf4518000454038745cf2a
This commit is contained in:
drh 2015-07-04 18:15:04 +00:00
parent 70c8885417
commit 01c5c00c12
4 changed files with 45 additions and 11 deletions
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16
manifest
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@ -1,5 +1,5 @@
C Fix\sa\sproblem\sin\sthe\sfts5\sintegrity-check.
D 2015-07-04T15:35:02.267
C Preserve\sthe\snumber\sof\srequested\sPAGECACHE\spages\seven\sif\sthe\smemory\spointer\nor\ssize\sis\szero.\s\sEnhance\sthe\spcache1.c\sheader\scomment\sto\sexplain\sthe\smemory\nlayout\sof\sa\spage\scache\sline.
D 2015-07-04T18:15:04.326
F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
F Makefile.in 017bf0511d1b2dd1db5e16488fbf75a17b526cbc
F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@ -293,7 +293,7 @@ F src/legacy.c ba1863ea58c4c840335a84ec276fc2b25e22bc4e
F src/lempar.c 92bafa308607dd985ca389a788cd9e0a2b608712
F src/loadext.c e722f4b832f923744788365df5fb8515c0bc8a47
F src/main.c 92d79bfa1a36c7c554700bb58eb8327abff1ac5c
F src/malloc.c 9be4e645f2fb411e5a04cf97e91f68b4faa6dc81
F src/malloc.c 19461e159bccf0e2cf06a50e867963d0a7b124a8
F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
F src/mem1.c abe6ee469b6c5a35c7f22bfeb9c9bac664a1c987
F src/mem2.c f1940d9e91948dd6a908fbb9ce3835c36b5d83c3
@ -319,7 +319,7 @@ F src/pager.h 6d435f563b3f7fcae4b84433b76a6ac2730036e2
F src/parse.y 6d60dda8f8d418b6dc034f1fbccd816c459983a8
F src/pcache.c cde06aa50962595e412d497e22fd2e07878ba1f0
F src/pcache.h 9968603796240cdf83da7e7bef76edf90619cea9
F src/pcache1.c 9ec20f98f50ed7415019303ae9bd3745d4b7bd9b
F src/pcache1.c b800e90896640bb0d1b0f6baa34fb059ca3b8b2e
F src/pragma.c c1f4d012ea9f6b1ce52d341b2cd0ad72d560afd7
F src/pragma.h b8632d7cdda7b25323fa580e3e558a4f0d4502cc
F src/prepare.c 82e5db1013846a819f198336fed72c44c974e7b1
@ -1364,7 +1364,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
P 743bf1f184be316971f2e9c651bcf573bde8654a
R 9bf7551534e5c2a541b49f913ee30aa3
U dan
Z 59b496d519385223221d6df6daef9f3a
P 4e473559c9bdcf4d0b823e995a3642cd50ebd337
R 3bd4765a55a11bf2fbafbabfd8169c43
U drh
Z 0199ebd97104f84a289dac04b3e8dc79

2
manifest.uuid
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@ -1 +1 @@
4e473559c9bdcf4d0b823e995a3642cd50ebd337
dacb2a615ce1c0573baf4518000454038745cf2a

3
src/malloc.c
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@ -193,10 +193,9 @@ int sqlite3MallocInit(void){
sqlite3GlobalConfig.nScratch = 0;
}
if( sqlite3GlobalConfig.pPage==0 || sqlite3GlobalConfig.szPage<512
|| sqlite3GlobalConfig.nPage<1 ){
|| sqlite3GlobalConfig.nPage<=0 ){
sqlite3GlobalConfig.pPage = 0;
sqlite3GlobalConfig.szPage = 0;
sqlite3GlobalConfig.nPage = 0;
}
rc = sqlite3GlobalConfig.m.xInit(sqlite3GlobalConfig.m.pAppData);
if( rc!=SQLITE_OK ) memset(&mem0, 0, sizeof(mem0));

35
src/pcache1.c
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@ -15,6 +15,41 @@
** of the SQLITE_CONFIG_PAGECACHE and sqlite3_release_memory() features.
** If the default page cache implementation is overridden, then neither of
** these two features are available.
**
** A Page cache line looks like this:
**
** -------------------------------------------------------------
** | database page content | PgHdr1 | MemPage | PgHdr |
** -------------------------------------------------------------
**
** The database page content is up front (so that buffer overreads tend to
** flow harmlessly into the PgHdr1, MemPage, and PgHdr extensions). MemPage
** is the extension added by the btree.c module containing information such
** as the database page number and how that database page is used. PgHdr
** is added by the pcache.c layer and contains information used to keep track
** of which pages are "dirty". PgHdr1 is an extension added by this
** module (pcache1.c). The PgHdr1 header is a subclass of sqlite3_pcache_page.
** PgHdr1 contains information needed to look up a page by its page number.
** The superclass sqlite3_pcache_page.pBuf points to the start of the
** database page content and sqlite3_pcache_page.pExtra points to PgHdr.
**
** The size of the extension (MemPage+PgHdr+PgHdr1) can be determined at
** runtime using sqlite3_config(SQLITE_CONFIG_PCACHE_HDRSZ, &size). The
** sizes of the extensions sum to 272 bytes on x64 for 3.8.10, but this
** size can vary according to architecture, compile-time options, and
** SQLite library version number.
**
** If SQLITE_PCACHE_SEPARATE_HEADER is defined, then the extension is obtained
** using a separate memory allocation from the database page content. This
** seeks to overcome the "clownfoot" problem of allocating a few bytes more
** than a power of two with the memory allocator rounding up to the next
** power of two, and leaving the rounded-up space unused.
**
** This module tracks pointers to PgHdr1 objects. Only pcache.c communicates
** with this module. Information is passed back and forth as PgHdr1 pointers.
**
** The pcache.c and pager.c modules deal pointers to PgHdr objects.
** The btree.c module deals with pointers to MemPage objects.
*/
#include "sqliteInt.h"