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Clarification of code comments in expr.c. Clean up the implementations

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of sqlite3ExprIsVector() and sqlite3ExprVectorSize() slightly.

FossilOrigin-Name: 4fb66d6592b141a4a71359250dbd1ac454569cb9
This commit is contained in:
drh
2016-08-20 21:02:38 +00:00
parent 8bd0d58e1c
commit 76dbe7a8d0
3 changed files with 21 additions and 21 deletions
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28
src/expr.c
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@@ -313,9 +313,7 @@ static int codeCompare(
** Return true if expression pExpr is a vector, or false otherwise.
*/
int sqlite3ExprIsVector(Expr *pExpr){
return ( (pExpr->op==TK_VECTOR)
|| (pExpr->op==TK_SELECT && pExpr->x.pSelect->pEList->nExpr>1)
);
return sqlite3ExprVectorSize(pExpr)>1;
}
/*
@@ -325,28 +323,30 @@ int sqlite3ExprIsVector(Expr *pExpr){
** any other type of expression, return 1.
*/
int sqlite3ExprVectorSize(Expr *pExpr){
if( sqlite3ExprIsVector(pExpr)==0 ) return 1;
if( pExpr->flags & EP_xIsSelect ){
if( pExpr->op==TK_VECTOR ){
return pExpr->x.pList->nExpr;
}else if( pExpr->op==TK_SELECT ){
return pExpr->x.pSelect->pEList->nExpr;
}else{
return 1;
}
return pExpr->x.pList->nExpr;
}
#ifndef SQLITE_OMIT_SUBQUERY
/*
** Interpret the pVector input as a vector expression. If pVector is
** an ordinary scalar expression, treat it as a vector of size 1.
**
** Return a pointer to a subexpression of pVector that is the i-th
** column of the vector (numbered starting with 0). The caller must
** ensure that i is within range.
**
** If pVector is really a scalar (and "scalar" here includes subqueries
** that return a single column!) then return pVector unmodified.
**
** pVector retains ownership of the returned subexpression.
**
** If the vector is a (SELECT ...) then the expression returned is
** just the expression for the i-th term of the result set, and is
** necessarily ready to be evaluated because the table cursor might
** not have been positioned yet.
** just the expression for the i-th term of the result set, and may
** not be ready for evaluation because the table cursor has not yet
** been positioned.
*/
Expr *sqlite3VectorFieldSubexpr(Expr *pVector, int i){
assert( i<sqlite3ExprVectorSize(pVector) );
@@ -374,10 +374,10 @@ Expr *sqlite3VectorFieldSubexpr(Expr *pVector, int i){
** ensuring that the returned value eventually gets freed.
**
** The caller retains ownership of pVector. If pVector is a TK_SELECT,
** then the return value will reference pVector and so pVector must remain
** then the returne object 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.
** returns.
**
** 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