SQLite

      if( pSel->pLimit ){
        sqlite3ExprDelete(pParse->db, pSel->pLimit->pLeft);
        pSel->pLimit->pLeft = pLimit;
      }else{
        pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
      }
      pSel->iLimit = 0;

      if( sqlite3Select(pParse, pSel, &dest) ){
        return 0;
      }
      rReg = dest.iSDParm;
      ExprSetVVAProperty(pExpr, EP_NoReduce);
      break;
    }

/*
** Handle the special case of a compound-select that originates from a
** VALUES clause.  By handling this as a special case, we avoid deep
** recursion, and thus do not need to enforce the SQLITE_LIMIT_COMPOUND_SELECT
** on a VALUES clause.
**
** Because the Select object originates from a VALUES clause:
**   (1) There is no LIMIT or OFFSET or else there is a LIMIT of exactly 1
**   (2) All terms are UNION ALL
**   (3) There is no ORDER BY clause
**
** The "LIMIT of exactly 1" case of condition (1) comes about when a VALUES
** clause occurs within scalar expression (ex: "SELECT (VALUES(1),(2),(3))").
** The sqlite3CodeSubselect will have added the LIMIT 1 clause in tht case.
** Since the limit is exactly 1, we only need to evalutes the left-most VALUES.
*/
static int multiSelectValues(
  Parse *pParse,        /* Parsing context */
  Select *p,            /* The right-most of SELECTs to be coded */
  SelectDest *pDest     /* What to do with query results */
){
  Select *pPrior;
  Select *pRightmost = p;
  int nRow = 1;
  int rc = 0;
  assert( p->selFlags & SF_MultiValue );
  do{
    assert( p->selFlags & SF_Values );
    assert( p->op==TK_ALL || (p->op==TK_SELECT && p->pPrior==0) );

    assert( p->pNext==0 || p->pEList->nExpr==p->pNext->pEList->nExpr );
    if( p->pPrior==0 ) break;
    assert( p->pPrior->pNext==p );
    p = p->pPrior;
    nRow++;
  }while(1);
  while( p ){
    pPrior = p->pPrior;
    p->pPrior = 0;
    rc = sqlite3Select(pParse, p, pDest);
    p->pPrior = pPrior;
    if( rc || pRightmost->pLimit ) break;
    p->nSelectRow = nRow;
    p = p->pNext;
  }
  return rc;
}

/*

  append sql "($i);"
  set microsec [lindex [time {db eval $sql}] 0]
  db eval {
    SELECT count(x), sum(x), avg(x), $microsec<10000000 FROM t1;
  }
} {100000 5000050000 50000.5 1}
  
# 2018-01-14.  A 100K-entry VALUES clause within a scalar expression does
# not cause processor stack overflow.
#
do_test 110 {
  set sql "SELECT (VALUES"
  for {set i 1} {$i<100000} {incr i} {
    append sql "($i),"
  }
  append sql "($i));"
  db eval $sql
} {1}

# Only the left-most term of a multi-valued VALUES within a scalar
# expression is evaluated.
#
do_test 120 {
  set n [llength [split [db eval "explain $sql"] \n]]
  expr {$n<10}
} {1}

finish_test