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Overview
| Comment: | OP_Column optimization: Do not check for an oversize row header unless the row header size is larger than the content available on the local page. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
8125b74cb46c372b9a319f6270f1c396 |
| User & Date: | drh 2015-10-16 12:53:47 |
Context
|
2015-10-16
| ||
| 13:50 | Simplify the OP_Column logic slightly. One very small performance improvement added. check-in: 0114b45d user: drh tags: trunk | |
| 12:53 | OP_Column optimization: Do not check for an oversize row header unless the row header size is larger than the content available on the local page. check-in: 8125b74c user: drh tags: trunk | |
| 12:39 | Improved header comment on the tool/vdbe_profile.tcl script. No changes to code. check-in: b17ad8fc user: drh tags: trunk | |
Changes
Changes to src/vdbe.c.
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}
}
pC->cacheStatus = p->cacheCtr;
pC->iHdrOffset = getVarint32(pC->aRow, offset);
pC->nHdrParsed = 0;
aOffset[0] = offset;
/* Make sure a corrupt database has not given us an oversize header.
** Do this now to avoid an oversize memory allocation.
**
** Type entries can be between 1 and 5 bytes each. But 4 and 5 byte
** types use so much data space that there can only be 4096 and 32 of
** them, respectively. So the maximum header length results from a
** 3-byte type for each of the maximum of 32768 columns plus three
** extra bytes for the header length itself. 32768*3 + 3 = 98307.
*/
if( offset > 98307 || offset > pC->payloadSize ){
rc = SQLITE_CORRUPT_BKPT;
goto op_column_error;
}
if( avail<offset ){
/* pC->aRow does not have to hold the entire row, but it does at least
** need to cover the header of the record. If pC->aRow does not contain
** the complete header, then set it to zero, forcing the header to be
** dynamically allocated. */
pC->aRow = 0;
pC->szRow = 0;
}
/* The following goto is an optimization. It can be omitted and
** everything will still work. But OP_Column is measurably faster
** by skipping the subsequent conditional, which is always true.
*/
assert( pC->nHdrParsed<=p2 ); /* Conditional skipped */
|
< < < < < < < < < < < < < > > > > > > > > > > > > > > |
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}
}
pC->cacheStatus = p->cacheCtr;
pC->iHdrOffset = getVarint32(pC->aRow, offset);
pC->nHdrParsed = 0;
aOffset[0] = offset;
if( avail<offset ){
/* pC->aRow does not have to hold the entire row, but it does at least
** need to cover the header of the record. If pC->aRow does not contain
** the complete header, then set it to zero, forcing the header to be
** dynamically allocated. */
pC->aRow = 0;
pC->szRow = 0;
/* Make sure a corrupt database has not given us an oversize header.
** Do this now to avoid an oversize memory allocation.
**
** Type entries can be between 1 and 5 bytes each. But 4 and 5 byte
** types use so much data space that there can only be 4096 and 32 of
** them, respectively. So the maximum header length results from a
** 3-byte type for each of the maximum of 32768 columns plus three
** extra bytes for the header length itself. 32768*3 + 3 = 98307.
*/
if( offset > 98307 || offset > pC->payloadSize ){
rc = SQLITE_CORRUPT_BKPT;
goto op_column_error;
}
}
/* The following goto is an optimization. It can be omitted and
** everything will still work. But OP_Column is measurably faster
** by skipping the subsequent conditional, which is always true.
*/
assert( pC->nHdrParsed<=p2 ); /* Conditional skipped */
|