SQLite

  j1 = sqlite3VdbeAddOp1(v, OP_Rewind, iCur); VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_Column, iCur, 0, regHasNull);
  sqlite3VdbeChangeP5(v, OPFLAG_TYPEOFARG);
  VdbeComment((v, "first_entry_in(%d)", iCur));
  sqlite3VdbeJumpHere(v, j1);
}


#ifndef SQLITE_OMIT_SUBQUERY
/*
** The argument is an IN operator with a list (not a subquery) on the 
** right-hand side.  Return TRUE if that list is constant.
*/
static int sqlite3InRhsIsConstant(Expr *pIn){
  Expr *pLHS;
  int res;
  assert( !ExprHasProperty(pIn, EP_xIsSelect) );
  pLHS = pIn->pLeft;
  pIn->pLeft = 0;
  res = sqlite3ExprIsConstant(pIn);
  pIn->pLeft = pLHS;
  return res;
}
#endif

/*
** This function is used by the implementation of the IN (...) operator.
** The pX parameter is the expression on the RHS of the IN operator, which
** might be either a list of expressions or a subquery.
**
** The job of this routine is to find or create a b-tree object that can
** be used either to test for membership in the RHS set or to iterate through
** all members of the RHS set, skipping duplicates.
**
** A cursor is opened on the b-tree object that is the RHS of the IN operator
** and pX->iTable is set to the index of that cursor.
**
** The returned value of this function indicates the b-tree type, as follows:
**
**   IN_INDEX_ROWID      - The cursor was opened on a database table.
**   IN_INDEX_INDEX_ASC  - The cursor was opened on an ascending index.
**   IN_INDEX_INDEX_DESC - The cursor was opened on a descending index.
**   IN_INDEX_EPH        - The cursor was opened on a specially created and
**                         populated epheremal table.
**   IN_INDEX_NOOP       - No cursor was allocated.  The IN operator must be
**                         implemented as a sequence of comparisons.
**
** An existing b-tree might be used if the RHS expression pX is a simple
** subquery such as:
**
**     SELECT <column> FROM <table>
**
** If the RHS of the IN operator is a list or a more complex subquery, then

** to be unique - either because it is an INTEGER PRIMARY KEY or it
** has a UNIQUE constraint or UNIQUE index.
**
** When IN_INDEX_MEMBERSHIP is used (and the b-tree will be used 
** for fast set membership tests) then an epheremal table must 
** be used unless <column> is an INTEGER PRIMARY KEY or an index can 
** be found with <column> as its left-most column.
**
** If the IN_INDEX_NOOP_OK and IN_INDEX_MEMBERSHIP are both set and
** if the RHS of the IN operator is a list (not a subquery) then this
** routine might decide that creating an ephemeral b-tree for membership
** testing is too expensive and return IN_INDEX_NOOP.  In that case, the
** calling routine should implement the IN operator using a sequence
** of Eq or Ne comparison operations.
**
** When the b-tree is being used for membership tests, the calling function
** might need to know whether or not the RHS side of the IN operator
** contains a NULL.  If prRhsHasNull is not a NULL pointer and 
** if there is any chance that the (...) might contain a NULL value at
** runtime, then a register is allocated and the register number written
** to *prRhsHasNull. If there is no chance that the (...) contains a

            sqlite3SetHasNullFlag(v, iTab, *prRhsHasNull);
          }
          sqlite3VdbeJumpHere(v, iAddr);
        }
      }
    }
  }

  /* If no preexisting index is available for the IN clause
  ** and IN_INDEX_NOOP is an allowed reply
  ** and the RHS of the IN operator is a list, not a subquery
  ** and the RHS is not contant or has two or fewer terms,
  ** then it is not worth creating an ephermeral table to evaluate
  ** the IN operator so return IN_INDEX_NOOP.
  */
  if( eType==0
   && (inFlags & IN_INDEX_NOOP_OK)
   && !ExprHasProperty(pX, EP_xIsSelect)
   && (!sqlite3InRhsIsConstant(pX) || pX->x.pList->nExpr<=2)
  ){
    eType = IN_INDEX_NOOP;
  }
     

  if( eType==0 ){
    /* Could not find an existing table or index to use as the RHS b-tree.
    ** We will have to generate an ephemeral table to do the job.
    */
    u32 savedNQueryLoop = pParse->nQueryLoop;
    int rMayHaveNull = 0;

  /* Compute the RHS.   After this step, the table with cursor
  ** pExpr->iTable will contains the values that make up the RHS.
  */
  v = pParse->pVdbe;
  assert( v!=0 );       /* OOM detected prior to this routine */
  VdbeNoopComment((v, "begin IN expr"));
  eType = sqlite3FindInIndex(pParse, pExpr,
                             IN_INDEX_MEMBERSHIP | IN_INDEX_NOOP_OK,
                             destIfFalse==destIfNull ? 0 : &rRhsHasNull);

  /* Figure out the affinity to use to create a key from the results
  ** of the expression. affinityStr stores a static string suitable for
  ** P4 of OP_MakeRecord.
  */
  affinity = comparisonAffinity(pExpr);

  /* Code the LHS, the <expr> from "<expr> IN (...)".
  */
  sqlite3ExprCachePush(pParse);
  r1 = sqlite3GetTempReg(pParse);
  sqlite3ExprCode(pParse, pExpr->pLeft, r1);

  /* If sqlite3FindInIndex() did not find or create an index that is
  ** suitable for evaluating the IN operator, then evaluate using a
  ** sequence of comparisons.
  */
  if( eType==IN_INDEX_NOOP ){
    ExprList *pList = pExpr->x.pList;
    CollSeq *pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
    int labelOk = sqlite3VdbeMakeLabel(v);
    int r2, regToFree;
    int regCkNull = 0;
    int ii;
    assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
    sqlite3VdbeAddOp2(v, OP_IsNull, r1, destIfNull); VdbeCoverage(v);
    if( destIfNull!=destIfFalse ){
      regCkNull = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp2(v, OP_Integer, 0, regCkNull);
    }
    for(ii=0; ii<pList->nExpr; ii++){
      r2 = sqlite3ExprCodeTemp(pParse, pList->a[ii].pExpr, &regToFree);
      if( regCkNull ){
        sqlite3VdbeAddOp3(v, OP_BitAnd, regCkNull, r2, regCkNull);
      }
      if( ii<pList->nExpr-1 || destIfNull!=destIfFalse ){
        sqlite3VdbeAddOp4(v, OP_Eq, r1, labelOk, r2,
                          (void*)pColl, P4_COLLSEQ); VdbeCoverage(v);
        sqlite3VdbeChangeP5(v, affinity);
      }else{
        assert( destIfNull==destIfFalse );
        sqlite3VdbeAddOp4(v, OP_Ne, r1, destIfFalse, r2,
                          (void*)pColl, P4_COLLSEQ); VdbeCoverage(v);
        sqlite3VdbeChangeP5(v, affinity | SQLITE_JUMPIFNULL);
      }
      sqlite3ReleaseTempReg(pParse, regToFree);
    }
    if( regCkNull ){
      sqlite3VdbeAddOp2(v, OP_IsNull, regCkNull, destIfNull); VdbeCoverage(v);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
    }
    sqlite3VdbeResolveLabel(v, labelOk);
    sqlite3ReleaseTempReg(pParse, regCkNull);
  }else{
  
    /* If the LHS is NULL, then the result is either false or NULL depending
    ** on whether the RHS is empty or not, respectively.
    */
    if( destIfNull==destIfFalse ){
      /* Shortcut for the common case where the false and NULL outcomes are
      ** the same. */
      sqlite3VdbeAddOp2(v, OP_IsNull, r1, destIfNull); VdbeCoverage(v);
    }else{
      int addr1 = sqlite3VdbeAddOp1(v, OP_NotNull, r1); VdbeCoverage(v);
      sqlite3VdbeAddOp2(v, OP_Rewind, pExpr->iTable, destIfFalse);
      VdbeCoverage(v);
      sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfNull);
      sqlite3VdbeJumpHere(v, addr1);
    }
  
    if( eType==IN_INDEX_ROWID ){
      /* In this case, the RHS is the ROWID of table b-tree
      */
      sqlite3VdbeAddOp2(v, OP_MustBeInt, r1, destIfFalse); VdbeCoverage(v);
      sqlite3VdbeAddOp3(v, OP_NotExists, pExpr->iTable, destIfFalse, r1);
      VdbeCoverage(v);
    }else{
      /* In this case, the RHS is an index b-tree.
      */
      sqlite3VdbeAddOp4(v, OP_Affinity, r1, 1, 0, &affinity, 1);
  
      /* If the set membership test fails, then the result of the 
      ** "x IN (...)" expression must be either 0 or NULL. If the set
      ** contains no NULL values, then the result is 0. If the set 
      ** contains one or more NULL values, then the result of the
      ** expression is also NULL.
      */
      assert( destIfFalse!=destIfNull || rRhsHasNull==0 );
      if( rRhsHasNull==0 ){
        /* This branch runs if it is known at compile time that the RHS
        ** cannot contain NULL values. This happens as the result
        ** of a "NOT NULL" constraint in the database schema.
        **
        ** Also run this branch if NULL is equivalent to FALSE
        ** for this particular IN operator.
        */
        sqlite3VdbeAddOp4Int(v, OP_NotFound, pExpr->iTable, destIfFalse, r1, 1);
        VdbeCoverage(v);
      }else{
        /* In this branch, the RHS of the IN might contain a NULL and
        ** the presence of a NULL on the RHS makes a difference in the
        ** outcome.
        */
        int j1;
  
        /* First check to see if the LHS is contained in the RHS.  If so,
        ** then the answer is TRUE the presence of NULLs in the RHS does
        ** not matter.  If the LHS is not contained in the RHS, then the
        ** answer is NULL if the RHS contains NULLs and the answer is
        ** FALSE if the RHS is NULL-free.
        */
        j1 = sqlite3VdbeAddOp4Int(v, OP_Found, pExpr->iTable, 0, r1, 1);
        VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_IsNull, rRhsHasNull, destIfNull);
        VdbeCoverage(v);
        sqlite3VdbeAddOp2(v, OP_Goto, 0, destIfFalse);
        sqlite3VdbeJumpHere(v, j1);
      }
    }
  }
  sqlite3ReleaseTempReg(pParse, r1);
  sqlite3ExprCachePop(pParse);
  VdbeComment((v, "end IN expr"));
}
#endif /* SQLITE_OMIT_SUBQUERY */

/*
** Allowed return values from sqlite3FindInIndex()
*/
#define IN_INDEX_ROWID        1   /* Search the rowid of the table */
#define IN_INDEX_EPH          2   /* Search an ephemeral b-tree */
#define IN_INDEX_INDEX_ASC    3   /* Existing index ASCENDING */
#define IN_INDEX_INDEX_DESC   4   /* Existing index DESCENDING */
#define IN_INDEX_NOOP         5   /* No table available. Use comparisons */
/*
** Allowed flags for the 3rd parameter to sqlite3FindInIndex().
*/
#define IN_INDEX_NOOP_OK     0x0001  /* OK to return IN_INDEX_NOOP */
#define IN_INDEX_MEMBERSHIP  0x0002  /* IN operator used for membership test */
#define IN_INDEX_LOOP        0x0004  /* IN operator used as a loop */
int sqlite3FindInIndex(Parse *, Expr *, u32, int*);

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  int sqlite3JournalOpen(sqlite3_vfs *, const char *, sqlite3_file *, int, int);
  int sqlite3JournalSize(sqlite3_vfs *);
  int sqlite3JournalCreate(sqlite3_file *);
  int sqlite3JournalExists(sqlite3_file *p);

  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/}
do_execsql_test in4-3.47 {
  SELECT * FROM t3 WHERE x NOT IN (10);
} {1 1 1}
do_execsql_test in4-3.48 {
  EXPLAIN
  SELECT * FROM t3 WHERE x NOT IN (10);

do_execsql_test tkt-80e031a00f.319 {SELECT 'c' NOT IN t7} 0
do_execsql_test tkt-80e031a00f.320 {SELECT 'c' IN t7n} 1
do_execsql_test tkt-80e031a00f.321 {SELECT 'd' NOT IN t7n} 0
do_execsql_test tkt-80e031a00f.322 {SELECT 'b' IN t8} 1
do_execsql_test tkt-80e031a00f.323 {SELECT 'c' NOT IN t8} 0
do_execsql_test tkt-80e031a00f.324 {SELECT 'c' IN t8n} 1
do_execsql_test tkt-80e031a00f.325 {SELECT 'd' NOT IN t8n} 0
do_execsql_test tkt-80e031a00f.326 {SELECT 'a' IN (NULL,'a')} 1
do_execsql_test tkt-80e031a00f.327 {SELECT 'a' IN (NULL,'b')} {{}}
do_execsql_test tkt-80e031a00f.328 {SELECT 'a' NOT IN (NULL,'a')} 0
do_execsql_test tkt-80e031a00f.329 {SELECT 'a' NOT IN (NULL,'b')} {{}}
#
# Row 4:
do_execsql_test tkt-80e031a00f.400 {SELECT 1 IN (2,3,4,null)} {{}}
do_execsql_test tkt-80e031a00f.401 {SELECT 1 NOT IN (2,3,4,null)} {{}}
do_execsql_test tkt-80e031a00f.402 {SELECT 'a' IN ('b','c',null,'d')} {{}}
do_execsql_test tkt-80e031a00f.403 {SELECT 'a' NOT IN (null,'b','c','d')} {{}}
do_execsql_test tkt-80e031a00f.404 {SELECT 1 IN t4n} {{}}