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Only use the direct-overflow-read optimization if all data from the overflow page in question is being read.

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FossilOrigin-Name: d8e1f75ddf10f3c0b21acd5455f90fdcea54a948
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dan
2014-03-20 18:56:35 +00:00
parent 926345e027
commit 9bc21b535e
4 changed files with 20 additions and 14 deletions
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4
src/btree.c
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@@ -3951,6 +3951,7 @@ static int accessPayload(
int iIdx = 0;
MemPage *pPage = pCur->apPage[pCur->iPage]; /* Btree page of current entry */
BtShared *pBt = pCur->pBt; /* Btree this cursor belongs to */
int bEnd; /* True if reading to end of data */
assert( pPage );
assert( pCur->eState==CURSOR_VALID );
@@ -3960,6 +3961,7 @@ static int accessPayload(
getCellInfo(pCur);
aPayload = pCur->info.pCell + pCur->info.nHeader;
nKey = (pPage->intKey ? 0 : (int)pCur->info.nKey);
bEnd = (offset+amt==nKey+pCur->info.nData);
if( NEVER(offset+amt > nKey+pCur->info.nData)
|| &aPayload[pCur->info.nLocal] > &pPage->aData[pBt->usableSize]
@@ -4064,6 +4066,7 @@ static int accessPayload(
** 3) the database is file-backed, and
** 4) there is no open write-transaction, and
** 5) the database is not a WAL database,
** 6) all data from the page is being read.
**
** then data can be read directly from the database file into the
** output buffer, bypassing the page-cache altogether. This speeds
@@ -4071,6 +4074,7 @@ static int accessPayload(
*/
if( (eOp&0x01)==0 /* (1) */
&& offset==0 /* (2) */
&& (bEnd || a==ovflSize) /* (6) */
&& pBt->inTransaction==TRANS_READ /* (4) */
&& (fd = sqlite3PagerFile(pBt->pPager))->pMethods /* (3) */
&& pBt->pPage1->aData[19]==0x01 /* (5) */