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| author | drh <drh@noemail.net> | 2015-10-15 19:21:51 +0000 |
|---|---|---|
| committer | drh <drh@noemail.net> | 2015-10-15 19:21:51 +0000 |
| commit | ce78bc6e7ed51ea1f4452b77f4415331b7c1ff23 (patch) | |
| tree | 877fb72fc7058cde5f6e52dd7cac09c1f5ecedfd /src/expr.c | |
| parent | fed7ac6f04fd2e314c90eec1f744e01429b09e95 (diff) | |
| download | sqlite-ce78bc6e7ed51ea1f4452b77f4415331b7c1ff23.tar.gz sqlite-ce78bc6e7ed51ea1f4452b77f4415331b7c1ff23.zip | |
Enhance the use of the column cache for UPDATE statements, making them
more efficient for the case where a column is modified to be an expression
of other unmodified columns.
FossilOrigin-Name: 871e091df651b2275a672c35ff938bd4b6db0d7f
Diffstat (limited to 'src/expr.c')
| -rw-r--r-- | src/expr.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/src/expr.c b/src/expr.c index b39dea2ea..a93bab991 100644 --- a/src/expr.c +++ b/src/expr.c @@ -2481,9 +2481,12 @@ void sqlite3ExprCodeGetColumnOfTable( /* ** Generate code that will extract the iColumn-th column from -** table pTab and store the column value in a register. An effort -** is made to store the column value in register iReg, but this is -** not guaranteed. The location of the column value is returned. +** table pTab and store the column value in a register. +** +** An effort is made to store the column value in register iReg. This +** is not garanteeed for GetColumn() - the result can be stored in +** any register. But the result is guaranteed to land in register iReg +** for GetColumnToReg(). ** ** There must be an open cursor to pTab in iTable when this routine ** is called. If iColumn<0 then code is generated that extracts the rowid. @@ -2494,7 +2497,7 @@ int sqlite3ExprCodeGetColumn( int iColumn, /* Index of the table column */ int iTable, /* The cursor pointing to the table */ int iReg, /* Store results here */ - u8 p5 /* P5 value for OP_Column */ + u8 p5 /* P5 value for OP_Column + FLAGS */ ){ Vdbe *v = pParse->pVdbe; int i; @@ -2516,6 +2519,17 @@ int sqlite3ExprCodeGetColumn( } return iReg; } +void sqlite3ExprCodeGetColumnToReg( + Parse *pParse, /* Parsing and code generating context */ + Table *pTab, /* Description of the table we are reading from */ + int iColumn, /* Index of the table column */ + int iTable, /* The cursor pointing to the table */ + int iReg /* Store results here */ +){ + int r1 = sqlite3ExprCodeGetColumn(pParse, pTab, iColumn, iTable, iReg, 0); + if( r1!=iReg ) sqlite3VdbeAddOp2(pParse->pVdbe, OP_SCopy, r1, iReg); +} + /* ** Clear all column cache entries. |