SQLite

         || (pProbe->nKeyCol==1 && pProbe->onError && eOp==WO_EQ) 
        ){
          pNew->wsFlags |= WHERE_ONEROW;
        }else{
          pNew->wsFlags |= WHERE_UNQ_WANTED;
        }
      }
      if( scan.iEquiv>1 ) pNew->wsFlags |= WHERE_TRANSCONS;
    }else if( eOp & WO_ISNULL ){
      pNew->wsFlags |= WHERE_COLUMN_NULL;
    }else if( eOp & (WO_GT|WO_GE) ){
      testcase( eOp & WO_GT );
      testcase( eOp & WO_GE );
      pNew->wsFlags |= WHERE_COLUMN_RANGE|WHERE_BTM_LIMIT;
      pNew->u.btree.nBtm = whereRangeVectorLen(

#define WHERE_AUTO_INDEX   0x00004000  /* Uses an ephemeral index */
#define WHERE_SKIPSCAN     0x00008000  /* Uses the skip-scan algorithm */
#define WHERE_UNQ_WANTED   0x00010000  /* WHERE_ONEROW would have been helpful*/
#define WHERE_PARTIALIDX   0x00020000  /* The automatic index is partial */
#define WHERE_IN_EARLYOUT  0x00040000  /* Perhaps quit IN loops early */
#define WHERE_BIGNULL_SORT 0x00080000  /* Column nEq of index is BIGNULL */
#define WHERE_IN_SEEKSCAN  0x00100000  /* Seek-scan optimization for IN */
#define WHERE_TRANSCONS    0x00200000  /* Uses a transitive constraint */

#endif /* !defined(SQLITE_WHEREINT_H) */

      }
    }else{
      pLevel->u.in.nIn = 0;
    }
    sqlite3DbFree(pParse->db, aiMap);
#endif
  }

  /* As an optimization, try to disable the WHERE clause term that is
  ** driving the index as it will always be true.  The correct answer is
  ** obtained regardless, but we might get the answer with fewer CPU cycles
  ** by omitting the term.
  **
  ** But do not disable the term unless we are certain that the term is
  ** not a transitive constraint.  For an example of where that does not
  ** work, see https://sqlite.org/forum/forumpost/eb8613976a (2021-05-04)
  */
  if( (pLevel->pWLoop->wsFlags & WHERE_TRANSCONS)==0
   || (pTerm->eOperator & WO_EQUIV)==0
  ){
    disableTerm(pLevel, pTerm);
  }

  return iReg;
}

/*
** Generate code that will evaluate all == and IN constraints for an
** index scan.
**

do_execsql_test transitive1-570 {
  SELECT * FROM c1 WHERE x=y AND z=y AND z='abc';
} {}
do_execsql_test transitive1-570eqp {
  EXPLAIN QUERY PLAN
  SELECT * FROM c1 WHERE x=y AND z=y AND z='abc';
} {/SEARCH c1 USING INDEX c1x/}

# 2021-05-04 forum https://sqlite.org/forum/forumpost/eb8613976a
reset_db
do_execsql_test transitive1-600 {
  CREATE TABLE t0(a0 INT, b1 INT);
  CREATE INDEX t0b1 ON t0(b1);
  CREATE TABLE t1(w,x,y,z3 INT);
  INSERT INTO t0(a0, b1) VALUES (0,1);
  INSERT INTO t1(w,x,y,z3) VALUES (7,8,9,1);
} {}
do_execsql_test transitive1-610 {
  SELECT ALL * FROM t0,t1 WHERE b1=z3 AND a0=z3;
} {}
do_execsql_test transitive1-620 {
  SELECT ALL * FROM t0,t1 WHERE likely(b1=z3) AND a0=z3;
} {}
do_execsql_test transitive1-630 {
  DROP TABLE t0;
  DROP TABLE t1;
  CREATE TABLE t0(c0 INT, c1 INT UNIQUE);
  CREATE TABLE t1(c0 INT);
  INSERT INTO t0(c0, c1) VALUES (0, 1);
  INSERT INTO t1(c0) VALUES (1);
  SELECT ALL * FROM t1 NATURAL JOIN t0 WHERE (t1.c0=t0.c1);
  SELECT ALL * FROM t1 NATURAL JOIN t0 WHERE (likely(t1.c0=t0.c1));
  SELECT ALL * FROM t1,t0 WHERE (likely(t1.c0=t0.c1) AND t1.c0=t0.c0);
} {}

finish_test