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Performance optimization and very slight size reduction for OP_Column.

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FossilOrigin-Name: 869c30e45cc87063be423c650f16b99e8adb3df0
This commit is contained in:
drh
2014-10-11 23:31:52 +00:00
parent d6176c4131
commit c81aa2e120
3 changed files with 24 additions and 15 deletions
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25
src/vdbe.c
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@@ -2332,14 +2332,6 @@ case OP_Column: {
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.
@@ -2354,6 +2346,22 @@ case OP_Column: {
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 */
goto op_column_read_header;
}
/* Make sure at least the first p2+1 entries of the header have been
@@ -2363,6 +2371,7 @@ case OP_Column: {
/* If there is more header available for parsing in the record, try
** to extract additional fields up through the p2+1-th field
*/
op_column_read_header:
if( pC->iHdrOffset<aOffset[0] ){
/* Make sure zData points to enough of the record to cover the header. */
if( pC->aRow==0 ){