/ Check-in [96269f01]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Simplifications to the SQLITE_KEEPNULL flag on VDBE comparison operators.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | rowvalue
Files: files | file ages | folders
SHA1: 96269f0179a7d8fa44ee278cef362962368c59ef
User & Date: drh 2016-09-05 15:02:41
Context
2016-09-05
19:57
Fix an assert() so that it does C-compiler does not combine an assert() conditional with a production code conditional and thereby confuse the mutation testing script. check-in: 2fa5288a user: drh tags: rowvalue
15:02
Simplifications to the SQLITE_KEEPNULL flag on VDBE comparison operators. check-in: 96269f01 user: drh tags: rowvalue
12:12
Do vector comparison size checking early - at name resolution time - to forestall future problems. check-in: ae127bcc user: drh tags: rowvalue
Changes
Hide Diffs Unified Diffs Show Whitespace Changes Patch

Changes to src/vdbe.c.

1908
1909
1910
1911
1912
1913
1914
1915

1916
1917
1918
1919
1920
1921
1922
1923
1924
1925

1926
1927
1928
1929
1930
1931
1932
....
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091





2092
2093




2094
2095
2096
2097
2098
2099
2100
** If SQLITE_NULLEQ is set in P5 then the result of comparison is always either
** true or false and is never NULL.  If both operands are NULL then the result
** of comparison is true.  If either operand is NULL then the result is false.
** If neither operand is NULL the result is the same as it would be if
** the SQLITE_NULLEQ flag were omitted from P5.
**
** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
** content of r[P2] is only set to 1 (true) if it was not previously NULL.

*/
/* Opcode: Ne P1 P2 P3 P4 P5
** Synopsis: IF r[P3]!=r[P1]
**
** This works just like the Eq opcode except that the jump is taken if
** the operands in registers P1 and P3 are not equal.  See the Eq opcode for
** additional information.
**
** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
** content of r[P2] is only set to 0 (false) if it was not previously NULL.

*/
/* Opcode: Lt P1 P2 P3 P4 P5
** Synopsis: IF r[P3]<r[P1]
**
** Compare the values in register P1 and P3.  If reg(P3)<reg(P1) then
** jump to address P2.  Or if the SQLITE_STOREP2 flag is set in P5 store
** the result of comparison (0 or 1 or NULL) into register P2.
................................................................................
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;

  if( pOp->p5 & SQLITE_STOREP2 ){
    pOut = &aMem[pOp->p2];
    iCompare = res;
    res2 = res2!=0;  /* For this path res2 must be exactly 0 or 1 */
    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 && (pOut->flags & MEM_Null)!=0 ){
      /* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
      ** and prevents OP_Ne from overwriting NULL with 0. */





      assert( pOp->opcode==OP_Ne || pOp->opcode==OP_Eq );
      assert( res2==0 || res2==1 );




      if( (pOp->opcode==OP_Eq)==res2 ) break;
    }
    memAboutToChange(p, pOut);
    MemSetTypeFlag(pOut, MEM_Int);
    pOut->u.i = res2;
    REGISTER_TRACE(pOp->p2, pOut);
  }else{







|
>









|
>







 







|

|
>
>
>
>
>


>
>
>
>







1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
....
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
** If SQLITE_NULLEQ is set in P5 then the result of comparison is always either
** true or false and is never NULL.  If both operands are NULL then the result
** of comparison is true.  If either operand is NULL then the result is false.
** If neither operand is NULL the result is the same as it would be if
** the SQLITE_NULLEQ flag were omitted from P5.
**
** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
** content of r[P2] is only changed if the new value is NULL or 0 (false).
** In other words, a prior r[P2] value will not be overwritten by 1 (true).
*/
/* Opcode: Ne P1 P2 P3 P4 P5
** Synopsis: IF r[P3]!=r[P1]
**
** This works just like the Eq opcode except that the jump is taken if
** the operands in registers P1 and P3 are not equal.  See the Eq opcode for
** additional information.
**
** If both SQLITE_STOREP2 and SQLITE_KEEPNULL flags are set then the
** content of r[P2] is only changed if the new value is NULL or 1 (true).
** In other words, a prior r[P2] value will not be overwritten by 0 (false).
*/
/* Opcode: Lt P1 P2 P3 P4 P5
** Synopsis: IF r[P3]<r[P1]
**
** Compare the values in register P1 and P3.  If reg(P3)<reg(P1) then
** jump to address P2.  Or if the SQLITE_STOREP2 flag is set in P5 store
** the result of comparison (0 or 1 or NULL) into register P2.
................................................................................
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;

  if( pOp->p5 & SQLITE_STOREP2 ){
    pOut = &aMem[pOp->p2];
    iCompare = res;
    res2 = res2!=0;  /* For this path res2 must be exactly 0 or 1 */
    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 ){
      /* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
      ** and prevents OP_Ne from overwriting NULL with 0.  This flag
      ** is only used in contexts where either:
      **   (1) op==OP_Eq && (r[P2]==NULL || r[P2]==0)
      **   (2) op==OP_Ne && (r[P2]==NULL || r[P2]==1)
      ** Therefore it is not necessary to check the content of r[P2] for
      ** NULL. */
      assert( pOp->opcode==OP_Ne || pOp->opcode==OP_Eq );
      assert( res2==0 || res2==1 );
      testcase( res2==0 && pOp->opcode==OP_Eq );
      testcase( res2==1 && pOp->opcode==OP_Eq );
      testcase( res2==0 && pOp->opcode==OP_Ne );
      testcase( res2==1 && pOp->opcode==OP_Ne );
      if( (pOp->opcode==OP_Eq)==res2 ) break;
    }
    memAboutToChange(p, pOut);
    MemSetTypeFlag(pOut, MEM_Int);
    pOut->u.i = res2;
    REGISTER_TRACE(pOp->p2, pOut);
  }else{