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Add an alternative application-defined pcache implementation and add test

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cases to permutations.test to invoke it.  Added the SQLITE_CONFIG_GETPCACHE
method to sqlite3_config(). (CVS 5920)

FossilOrigin-Name: 16f1e6ec2ad92f68c0079a0c2b5ca08a3b4af816
This commit is contained in:
drh
2008-11-19 01:20:26 +00:00
parent 4c6517848f
commit b232c23297
9 changed files with 606 additions and 19 deletions
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438
src/test_pcache.c Normal file
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/*
** 2008 November 18
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code used for testing the SQLite system.
** None of the code in this file goes into a deliverable build.
**
** This file contains an application-defined pager cache
** implementation that can be plugged in in place of the
** default pcache. This alternative pager cache will throw
** some errors that the default cache does not.
**
** This pagecache implementation is designed for simplicity
** not speed.
**
** $Id: test_pcache.c,v 1.1 2008/11/19 01:20:26 drh Exp $
*/
#include "sqlite3.h"
#include <string.h>
#include <assert.h>
/*
** Global data used by this test implementation. There is no
** mutexing, which means this page cache will not work in a
** multi-threaded test.
*/
typedef struct testpcacheGlobalType testpcacheGlobalType;
struct testpcacheGlobalType {
void *pDummy; /* Dummy allocation to simulate failures */
int nInstance; /* Number of current instances */
unsigned discardChance; /* Chance of discarding on an unpin */
unsigned prngSeed; /* Seed for the PRNG */
};
static testpcacheGlobalType testpcacheGlobal;
/*
** Initializer.
**
** Verify that the initializer is only called when the system is
** uninitialized. Allocate some memory and report SQLITE_NOMEM if
** the allocation fails. This provides a means to test the recovery
** from a failed initialization attempt. It also verifies that the
** the destructor always gets call - otherwise there would be a
** memory leak.
*/
static int testpcacheInit(void *pArg){
assert( pArg==(void*)&testpcacheGlobal );
assert( testpcacheGlobal.pDummy==0 );
assert( testpcacheGlobal.nInstance==0 );
testpcacheGlobal.pDummy = sqlite3_malloc(10);
return testpcacheGlobal.pDummy==0 ? SQLITE_NOMEM : SQLITE_OK;
}
/*
** Destructor
**
** Verify that this is only called after initialization.
** Free the memory allocated by the initializer.
*/
static void testpcacheShutdown(void *pArg){
assert( pArg==(void*)&testpcacheGlobal );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance==0 );
sqlite3_free( testpcacheGlobal.pDummy );
testpcacheGlobal.pDummy = 0;
}
/*
** Number of pages in a cache
*/
#define TESTPCACHE_NPAGE 217
#define TESTPCACHE_RESERVE 17
/*
** Magic numbers used to determine validity of the page cache.
*/
#define TESTPCACHE_VALID 0x364585fd
#define TESTPCACHE_CLEAR 0xd42670d4
/*
** Private implementation of a page cache.
*/
typedef struct testpcache testpcache;
struct testpcache {
int szPage; /* Size of each page. Multiple of 8. */
int bPurgeable; /* True if the page cache is purgeable */
int nFree; /* Number of unused slots in a[] */
int nPinned; /* Number of pinned slots in a[] */
unsigned iRand; /* State of the PRNG */
unsigned iMagic; /* Magic number for sanity checking */
struct testpcachePage {
unsigned key; /* The key for this page. 0 means unallocated */
int isPinned; /* True if the page is pinned */
void *pData; /* Data for this page */
} a[TESTPCACHE_NPAGE]; /* All pages in the cache */
};
/*
** Get a random number using the PRNG in the given page cache.
*/
static unsigned testpcacheRandom(testpcache *p){
unsigned x = 0;
int i;
for(i=0; i<4; i++){
p->iRand = (p->iRand*69069 + 5);
x = (x<<8) | ((p->iRand>>16)&0xff);
}
return x;
}
/*
** Allocate a new page cache instance.
*/
static sqlite3_pcache *testpcacheCreate(int szPage, int bPurgeable){
int nMem;
char *x;
testpcache *p;
int i;
assert( testpcacheGlobal.pDummy!=0 );
szPage = (szPage+7)&~7;
nMem = sizeof(testpcache) + TESTPCACHE_NPAGE*szPage;
p = sqlite3_malloc( nMem );
if( p==0 ) return 0;
x = (char*)&p[1];
p->szPage = szPage;
p->nFree = TESTPCACHE_NPAGE;
p->nPinned = 0;
p->iRand = testpcacheGlobal.prngSeed;
p->bPurgeable = bPurgeable;
p->iMagic = TESTPCACHE_VALID;
for(i=0; i<TESTPCACHE_NPAGE; i++, x += szPage){
p->a[i].key = 0;
p->a[i].isPinned = 0;
p->a[i].pData = (void*)x;
}
testpcacheGlobal.nInstance++;
return (sqlite3_pcache*)p;
}
/*
** Set the cache size
*/
static void testpcacheCachesize(sqlite3_pcache *pCache, int newSize){
testpcache *p = (testpcache*)pCache;
assert( p->iMagic==TESTPCACHE_VALID );
assert( newSize>=1 );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
}
/*
** Return the number of pages in the cache that are being used.
** This includes both pinned and unpinned pages.
*/
static int testpcachePagecount(sqlite3_pcache *pCache){
testpcache *p = (testpcache*)pCache;
assert( p->iMagic==TESTPCACHE_VALID );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
return TESTPCACHE_NPAGE - p->nFree;
}
/*
** Fetch a page.
*/
static void *testpcacheFetch(
sqlite3_pcache *pCache,
unsigned key,
int createFlag
){
testpcache *p = (testpcache*)pCache;
int i, j;
assert( p->iMagic==TESTPCACHE_VALID );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
/* See if the page is already in cache. Return immediately if it is */
for(i=0; i<TESTPCACHE_NPAGE; i++){
if( p->a[i].key==key ){
if( !p->a[i].isPinned ){
p->nPinned++;
assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
p->a[i].isPinned = 1;
}
return p->a[i].pData;
}
}
/* If createFlag is 0, never allocate a new page */
if( createFlag==0 ){
return 0;
}
/* If no pages are available, always fail */
if( p->nPinned==TESTPCACHE_NPAGE ){
return 0;
}
/* Do not allocate the last TESTPCACHE_RESERVE pages unless createFlag is 2 */
if( p->nPinned>=TESTPCACHE_NPAGE-TESTPCACHE_RESERVE && createFlag<2 ){
return 0;
}
/* Find a free page to allocate if there are any free pages.
** Withhold TESTPCACHE_RESERVE free pages until createFlag is 2.
*/
if( p->nFree>TESTPCACHE_RESERVE || (createFlag==2 && p->nFree>0) ){
j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
if( p->a[j].key==0 ){
p->a[j].key = key;
p->a[j].isPinned = 1;
memset(p->a[j].pData, 0, p->szPage);
p->nPinned++;
p->nFree--;
assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
return p->a[j].pData;
}
}
/* The prior loop always finds a freepage to allocate */
assert( 0 );
}
/* If this cache is not purgeable then we have to fail.
*/
if( p->bPurgeable==0 ){
return 0;
}
/* If there are no free pages, recycle a page. The page to
** recycle is selected at random from all unpinned pages.
*/
j = testpcacheRandom(p) % TESTPCACHE_NPAGE;
for(i=0; i<TESTPCACHE_NPAGE; i++, j = (j+1)%TESTPCACHE_NPAGE){
if( p->a[j].key>0 && p->a[j].isPinned==0 ){
p->a[j].key = key;
p->a[j].isPinned = 1;
memset(p->a[j].pData, 0, p->szPage);
p->nPinned++;
assert( p->nPinned <= TESTPCACHE_NPAGE - p->nFree );
return p->a[j].pData;
}
}
/* The previous loop always finds a page to recycle. */
assert(0);
return 0;
}
/*
** Unpin a page.
*/
static void testpcacheUnpin(
sqlite3_pcache *pCache,
void *pOldPage,
int discard
){
testpcache *p = (testpcache*)pCache;
int i;
assert( p->iMagic==TESTPCACHE_VALID );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
/* Randomly discard pages as they are unpinned according to the
** discardChance setting. If discardChance is 0, the random discard
** never happens. If discardChance is 100, it always happens.
*/
if( p->bPurgeable
&& (100-testpcacheGlobal.discardChance) <= (testpcacheRandom(p)%100)
){
discard = 1;
}
for(i=0; i<TESTPCACHE_NPAGE; i++){
if( p->a[i].pData==pOldPage ){
/* The pOldPage pointer always points to a pinned page */
assert( p->a[i].isPinned );
p->a[i].isPinned = 0;
p->nPinned--;
assert( p->nPinned>=0 );
if( discard ){
p->a[i].key = 0;
p->nFree++;
assert( p->nFree<=TESTPCACHE_NPAGE );
}
return;
}
}
/* The pOldPage pointer always points to a valid page */
assert( 0 );
}
/*
** Rekey a single page.
*/
static void testpcacheRekey(
sqlite3_pcache *pCache,
void *pOldPage,
unsigned oldKey,
unsigned newKey
){
testpcache *p = (testpcache*)pCache;
int i;
assert( p->iMagic==TESTPCACHE_VALID );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
/* If there already exists another page at newKey, verify that
** the other page is unpinned and discard it.
*/
for(i=0; i<TESTPCACHE_NPAGE; i++){
if( p->a[i].key==newKey ){
/* The new key is never a page that is already pinned */
assert( p->a[i].isPinned==0 );
p->a[i].key = 0;
p->nFree++;
assert( p->nFree<=TESTPCACHE_NPAGE );
break;
}
}
/* Find the page to be rekeyed and rekey it.
*/
for(i=0; i<TESTPCACHE_NPAGE; i++){
if( p->a[i].key==oldKey ){
/* The oldKey and pOldPage parameters match */
assert( p->a[i].pData==pOldPage );
/* Page to be rekeyed must be pinned */
assert( p->a[i].isPinned );
p->a[i].key = newKey;
return;
}
}
/* Rekey is always given a valid page to work with */
assert( 0 );
}
/*
** Truncate the page cache. Every page with a key of iLimit or larger
** is discarded.
*/
static void testpcacheTruncate(sqlite3_pcache *pCache, unsigned iLimit){
testpcache *p = (testpcache*)pCache;
unsigned int i;
assert( p->iMagic==TESTPCACHE_VALID );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
for(i=0; i<TESTPCACHE_NPAGE; i++){
if( p->a[i].key>=iLimit ){
p->a[i].key = 0;
if( p->a[i].isPinned ){
p->nPinned--;
assert( p->nPinned>=0 );
}
p->nFree++;
assert( p->nFree<=TESTPCACHE_NPAGE );
}
}
}
/*
** Destroy a page cache.
*/
static void testpcacheDestroy(sqlite3_pcache *pCache){
testpcache *p = (testpcache*)pCache;
assert( p->iMagic==TESTPCACHE_VALID );
assert( testpcacheGlobal.pDummy!=0 );
assert( testpcacheGlobal.nInstance>0 );
p->iMagic = TESTPCACHE_CLEAR;
sqlite3_free(p);
testpcacheGlobal.nInstance--;
}
/*
** Invoke this routine to register or unregister the testing pager cache
** implemented by this file.
**
** Install the test pager cache if installFlag is 1 and uninstall it if
** installFlag is 0.
**
** When installing, discardChance is a number between 0 and 100 that
** indicates the probability of discarding a page when unpinning the
** page. 0 means never discard (unless the discard flag is set).
** 100 means always discard.
*/
void installTestPCache(
int installFlag, /* True to install. False to uninstall. */
unsigned discardChance, /* 0-100. Chance to discard on unpin */
unsigned prngSeed /* Seed for the PRNG */
){
static const sqlite3_pcache_methods testPcache = {
(void*)&testpcacheGlobal,
testpcacheInit,
testpcacheShutdown,
testpcacheCreate,
testpcacheCachesize,
testpcachePagecount,
testpcacheFetch,
testpcacheUnpin,
testpcacheRekey,
testpcacheTruncate,
testpcacheDestroy,
};
static sqlite3_pcache_methods defaultPcache;
static int isInstalled = 0;
assert( testpcacheGlobal.nInstance==0 );
assert( testpcacheGlobal.pDummy==0 );
assert( discardChance<=100 );
testpcacheGlobal.discardChance = discardChance;
testpcacheGlobal.prngSeed = prngSeed ^ (prngSeed<<16);
if( installFlag!=isInstalled ){
if( installFlag ){
sqlite3_config(SQLITE_CONFIG_GETPCACHE, &defaultPcache);
assert( defaultPcache.xCreate!=testpcacheCreate );
sqlite3_config(SQLITE_CONFIG_PCACHE, &testPcache);
}else{
assert( defaultPcache.xCreate!=0 );
sqlite3_config(SQLITE_CONFIG_PCACHE, &defaultPcache);
}
isInstalled = installFlag;
}
}