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FossilOrigin-Name: 4165d20f64d778a4e48f511a37cfced8579d4dbe
This commit is contained in:
drh
2016-08-20 01:06:22 +00:00
parent a1251bc40d
commit 8762ec1935
3 changed files with 27 additions and 15 deletions
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28
src/expr.c
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@@ -367,11 +367,21 @@ Expr *sqlite3VectorFieldSubexpr(Expr *pVector, int i){
** sqlite3ExprCode() will generate all necessary code to compute
** the iField-th column of the vector expression pVector.
**
** It is ok for pVector to be a scalar (as long as iField==0).
** In that case, this routine works like sqlite3ExprDup().
**
** The caller owns the returned Expr object and is responsible for
** ensuring that the returned value eventually gets freed.
**
** The caller retains ownership of pVector and must ensure that pVector
** remains valid as long as the returned value is in use.
** The caller retains ownership of pVector. If pVector is a TK_SELECT,
** then the return value will reference pVector and so pVector must remain
** valid for the life of the returned object. If pVector is a TK_VECTOR
** or a scalar expression, then it can be deleted as soon as this routine
** routines.
**
** A trick to cause a TK_SELECT pVector to be deleted together with
** the returned Expr object is to attach the pVector to the pRight field
** of the returned TK_SELECT_COLUMN Expr object.
*/
Expr *sqlite3ExprForVectorField(
Parse *pParse, /* Parsing context */
@@ -384,16 +394,17 @@ Expr *sqlite3ExprForVectorField(
/* The TK_SELECT_COLUMN Expr node:
**
** pLeft: pVector containing TK_SELECT
** pRight: pVector if ownership taken
** pRight: not used. But recursively deleted.
** iColumn: Index of a column in pVector
** pLeft->iTable: First in an array of register holding result, or 0
** if the result is not yet computed.
**
** sqlite3ExprDelete() specifically skips the recursive delete of
** pLeft on TK_SELECT_COLUMN nodes. But pRight is followed, so pVector
** is included on pRight if ownership is taken. Typically there will
** be multiple TK_SELECT_COLUMN nodes with the same pLeft pointer to
** the pVector, but only one of them will own the pVector.
** can be attached to pRight to cause this node to take ownership of
** pVector. Typically there will be multiple TK_SELECT_COLUMN nodes
** with the same pLeft pointer to the pVector, but only one of them
** will own the pVector.
*/
pRet = sqlite3PExpr(pParse, TK_SELECT_COLUMN, pVector, 0, 0);
if( pRet ) pRet->iColumn = iField;
@@ -1436,13 +1447,14 @@ no_mem:
}
/*
** pColumns and pExpr for a vector assignment, like this:
** pColumns and pExpr form a vector assignment which is part of the SET
** clause of an UPDATE statement. Like this:
**
** (a,b,c) = (expr1,expr2,expr3)
** Or: (a,b,c) = (SELECT x,y,z FROM ....)
**
** For each term of the vector assignment, append new entries to the
** expression list. In the case of a subquery on the LHS, append
** expression list pList. In the case of a subquery on the LHS, append
** TK_SELECT_COLUMN expressions.
*/
ExprList *sqlite3ExprListAppendVector(