SQLite

** CREATE TABLE t1(a);
** SELECT * FROM t1 WHERE a;
** SELECT a AS b FROM t1 WHERE b;
** SELECT * FROM t1 WHERE (select a from t1);
*/
char sqlite3ExprAffinity(Expr *pExpr){
  int op;
  if( pExpr->flags & EP_Generic ) return 0;
  while( ExprHasProperty(pExpr, EP_Skip) ){
    assert( pExpr->op==TK_COLLATE );
    pExpr = pExpr->pLeft;
    assert( pExpr!=0 );
  }
  op = pExpr->op;
  if( op==TK_SELECT ){

*/
CollSeq *sqlite3ExprCollSeq(Parse *pParse, Expr *pExpr){
  sqlite3 *db = pParse->db;
  CollSeq *pColl = 0;
  Expr *p = pExpr;
  while( p ){
    int op = p->op;
    if( p->flags & EP_Generic ) break;
    if( op==TK_REGISTER ) op = p->op2;
    if( (op==TK_AGG_COLUMN || op==TK_COLUMN || op==TK_TRIGGER)
     && p->y.pTab!=0
    ){
      /* op==TK_REGISTER && p->y.pTab!=0 happens when pExpr was originally
      ** a TK_COLUMN but was previously evaluated and cached in a register */
      int j = p->iColumn;

      **      expr1 NOT IN ()
      **
      ** simplify to constants 0 (false) and 1 (true), respectively,
      ** regardless of the value of expr1.
      */
      sqlite3ExprUnmapAndDelete(pParse, A);
      A = sqlite3ExprAlloc(pParse->db, TK_INTEGER,&sqlite3IntTokens[N],1);
    }else if( Y->nExpr==1 ){
      /* Expressions of the form:
      **
      **      expr1 IN (?1)
      **      expr1 NOT IN (?2)
      **
      ** with exactly one value on the RHS can be simplified to something
      ** like this:
      **
      **      expr1 == ?1
      **      expr1 <> ?2
      **
      ** But, the RHS of the == or <> is marked with the EP_Generic flag
      ** so that it may not contribute to the computation of comparison
      ** affinity or the collating sequence to use for comparison.  Otherwise,
      ** the semantics would be subtly different from IN or NOT IN.
      */
      Expr *pRHS = Y->a[0].pExpr;
      Y->a[0].pExpr = 0;
      sqlite3ExprListDelete(pParse->db, Y);
      /* pRHS cannot be NULL because a malloc error would have been detected
      ** before now and control would have never reached this point */
      if( ALWAYS(pRHS) ){
        pRHS->flags &= ~EP_Collate;
        pRHS->flags |= EP_Generic;
      }
      A = sqlite3PExpr(pParse, N ? TK_NE : TK_EQ, A, pRHS);
    }else{
      A = sqlite3PExpr(pParse, TK_IN, A, 0);
      if( A ){
        A->x.pList = Y;
        sqlite3ExprSetHeightAndFlags(pParse, A);
      }else{
        sqlite3ExprListDelete(pParse->db, Y);

        if( pNew && pSubst->isLeftJoin ){
          ExprSetProperty(pNew, EP_CanBeNull);
        }
        if( pNew && ExprHasProperty(pExpr,EP_FromJoin) ){
          pNew->iRightJoinTable = pExpr->iRightJoinTable;
          ExprSetProperty(pNew, EP_FromJoin);
        }
        if( pNew && ExprHasProperty(pExpr,EP_Generic) ){
          ExprSetProperty(pNew, EP_Generic);
        }
        sqlite3ExprDelete(db, pExpr);
        pExpr = pNew;
      }
    }
  }else{
    if( pExpr->op==TK_IF_NULL_ROW && pExpr->iTable==pSubst->iTable ){
      pExpr->iTable = pSubst->iNewTable;

#define EP_HasFunc    0x000004 /* Contains one or more functions of any kind */
#define EP_FixedCol   0x000008 /* TK_Column with a known fixed value */
#define EP_Agg        0x000010 /* Contains one or more aggregate functions */
#define EP_VarSelect  0x000020 /* pSelect is correlated, not constant */
#define EP_DblQuoted  0x000040 /* token.z was originally in "..." */
#define EP_InfixFunc  0x000080 /* True for an infix function: LIKE, GLOB, etc */
#define EP_Collate    0x000100 /* Tree contains a TK_COLLATE operator */
#define EP_Generic    0x000200 /* Ignore COLLATE or affinity on this tree */
#define EP_IntValue   0x000400 /* Integer value contained in u.iValue */
#define EP_xIsSelect  0x000800 /* x.pSelect is valid (otherwise x.pList is) */
#define EP_Skip       0x001000 /* Operator does not contribute to affinity */
#define EP_Reduced    0x002000 /* Expr struct EXPR_REDUCEDSIZE bytes only */
#define EP_TokenOnly  0x004000 /* Expr struct EXPR_TOKENONLYSIZE bytes only */
#define EP_Win        0x008000 /* Contains window functions */
#define EP_MemToken   0x010000 /* Need to sqlite3DbFree() Expr.zToken */

  assert( pOp->opcode!=OP_Next || pOp->p4.xAdvance==sqlite3BtreeNext );
  assert( pOp->opcode!=OP_Prev || pOp->p4.xAdvance==sqlite3BtreePrevious );

  /* The Next opcode is only used after SeekGT, SeekGE, Rewind, and Found.
  ** The Prev opcode is only used after SeekLT, SeekLE, and Last. */
  assert( pOp->opcode!=OP_Next
       || pC->seekOp==OP_SeekGT || pC->seekOp==OP_SeekGE
       || pC->seekOp==OP_Rewind || pC->seekOp==OP_Found 
       || pC->seekOp==OP_NullRow|| pC->seekOp==OP_SeekRowid);

  assert( pOp->opcode!=OP_Prev
       || pC->seekOp==OP_SeekLT || pC->seekOp==OP_SeekLE
       || pC->seekOp==OP_Last 
       || pC->seekOp==OP_NullRow);

  rc = pOp->p4.xAdvance(pC->uc.pCursor, pOp->p3);
next_tail:
  pC->cacheStatus = CACHE_STALE;
  VdbeBranchTaken(rc==SQLITE_OK,2);
  if( rc==SQLITE_OK ){

        ** first such term in use, and sets nIn back to 0 if it is not. */
        for(i=0; i<pNew->nLTerm-1; i++){
          if( pNew->aLTerm[i] && pNew->aLTerm[i]->pExpr==pExpr ) nIn = 0;
        }
      }else if( ALWAYS(pExpr->x.pList && pExpr->x.pList->nExpr) ){
        /* "x IN (value, value, ...)" */
        nIn = sqlite3LogEst(pExpr->x.pList->nExpr);
        assert( nIn>0 );  /* RHS always has 2 or more terms...  The parser
                          ** changes "x IN (?)" into "x=?". */
      }
      if( pProbe->hasStat1 ){
        LogEst M, logK, safetyMargin;
        /* Let:
        **   N = the total number of rows in the table
        **   K = the number of entries on the RHS of the IN operator
        **   M = the number of rows in the table that match terms to the 

do_execsql_test in4-3.42 {
  EXPLAIN
  SELECT * FROM t3 WHERE x IN (10,11);
} {/OpenEphemeral/}
do_execsql_test in4-3.43 {
  SELECT * FROM t3 WHERE x IN (10);
} {10 10 10}



do_execsql_test in4-3.44 {
  EXPLAIN
  SELECT * FROM t3 WHERE x IN (10);
} {~/OpenEphemeral/}
do_execsql_test in4-3.45 {
  SELECT * FROM t3 WHERE x NOT IN (10,11,99999);
} {1 1 1}
do_execsql_test in4-3.46 {
  EXPLAIN
  SELECT * FROM t3 WHERE x NOT IN (10,11,99999);
} {/OpenEphemeral/}

  INSERT INTO t6b VALUES(4,44),(5,55),(6,66);

  SELECT * FROM t6a, t6b WHERE a=3 AND b IN (c);
} {3 4 4 44}
do_execsql_test in4-6.1-eqp {
  EXPLAIN QUERY PLAN
  SELECT * FROM t6a, t6b WHERE a=3 AND b IN (c);
} {~/SCAN/}
do_execsql_test in4-6.2 {
  SELECT * FROM t6a, t6b WHERE a=3 AND c IN (b);
} {3 4 4 44}
do_execsql_test in4-6.2-eqp {
  EXPLAIN QUERY PLAN
  SELECT * FROM t6a, t6b WHERE a=3 AND c IN (b);
} {~/SCAN/}


finish_test