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Overview
Comment:Attempt the constant propagation optimization on any WHERE clause that has a top-level AND operator, even if the query is not a join. This is an attempt to partially address the concern raised in forum post 830d37b928.
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SHA3-256: e994c9f29f7a561dd5f30573865b0f793fb1388af09a2afb9b1a5b037ea52f89
User & Date: drh 2021-05-14 14:26:57
Context
2021-05-14
15:37
Avoid adding superfluous virtual WHERE clause terms that might arise due to the constant propagation optimization. (check-in: cf63abbe user: drh tags: trunk)
14:26
Attempt the constant propagation optimization on any WHERE clause that has a top-level AND operator, even if the query is not a join. This is an attempt to partially address the concern raised in forum post 830d37b928. (check-in: e994c9f2 user: drh tags: trunk)
13:32
Fix an over-length source code comment in whereexpr.c. No logic changes. (check-in: af5eb902 user: drh tags: trunk)
Changes
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Changes to src/select.c.

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** Find all terms of COLUMN=VALUE or VALUE=COLUMN in pExpr where VALUE
** is a constant expression and where the term must be true because it
** is part of the AND-connected terms of the expression.  For each term
** found, add it to the pConst structure.
*/
static void findConstInWhere(WhereConst *pConst, Expr *pExpr){
  Expr *pRight, *pLeft;
  if( pExpr==0 ) return;
  if( ExprHasProperty(pExpr, EP_FromJoin) ) return;
  if( pExpr->op==TK_AND ){
    findConstInWhere(pConst, pExpr->pRight);
    findConstInWhere(pConst, pExpr->pLeft);
    return;
  }
  if( pExpr->op!=TK_EQ ) return;







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** Find all terms of COLUMN=VALUE or VALUE=COLUMN in pExpr where VALUE
** is a constant expression and where the term must be true because it
** is part of the AND-connected terms of the expression.  For each term
** found, add it to the pConst structure.
*/
static void findConstInWhere(WhereConst *pConst, Expr *pExpr){
  Expr *pRight, *pLeft;
  if( NEVER(pExpr==0) ) return;
  if( ExprHasProperty(pExpr, EP_FromJoin) ) return;
  if( pExpr->op==TK_AND ){
    findConstInWhere(pConst, pExpr->pRight);
    findConstInWhere(pConst, pExpr->pLeft);
    return;
  }
  if( pExpr->op!=TK_EQ ) return;
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#endif

  /* Do the WHERE-clause constant propagation optimization if this is
  ** a join.  No need to speed time on this operation for non-join queries
  ** as the equivalent optimization will be handled by query planner in
  ** sqlite3WhereBegin().
  */
  if( pTabList->nSrc>1

   && OptimizationEnabled(db, SQLITE_PropagateConst)
   && propagateConstants(pParse, p)
  ){
#if SELECTTRACE_ENABLED
    if( sqlite3SelectTrace & 0x100 ){
      SELECTTRACE(0x100,pParse,p,("After constant propagation:\n"));
      sqlite3TreeViewSelect(0, p, 0);







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#endif

  /* Do the WHERE-clause constant propagation optimization if this is
  ** a join.  No need to speed time on this operation for non-join queries
  ** as the equivalent optimization will be handled by query planner in
  ** sqlite3WhereBegin().
  */
  if( p->pWhere!=0
   && p->pWhere->op==TK_AND
   && OptimizationEnabled(db, SQLITE_PropagateConst)
   && propagateConstants(pParse, p)
  ){
#if SELECTTRACE_ENABLED
    if( sqlite3SelectTrace & 0x100 ){
      SELECTTRACE(0x100,pParse,p,("After constant propagation:\n"));
      sqlite3TreeViewSelect(0, p, 0);