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Overview
Comment:Allow virtual table implementations to handle OFFSET but not LIMIT, but not LIMIT but not OFFSET.
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Timelines: family | ancestors | descendants | both | vtab-limit-fix
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SHA3-256: 90e5c8226a695e838e8c1703a9b8598e654d216799e8806c4d1a1f20c28c6486
User & Date: dan 2024-04-26 18:13:11
Context
2024-04-26
19:10
Fix issues in LIMIT/OFFSET support for virtual tables. The first problem was reported by forum post c243b8f856. That report prompted an enhancement to the generate_series() (also included in this merge) which in turn identified other similar issues. (check-in: 5f6c079d user: drh tags: trunk)
18:13
Allow virtual table implementations to handle OFFSET but not LIMIT, but not LIMIT but not OFFSET. (Closed-Leaf check-in: 90e5c822 user: dan tags: vtab-limit-fix)
17:19
Have where.c ignore any plan from a virtual table that tries to use LIMIT/OFFSET without also using all WHERE constraints. (check-in: 7d305964 user: dan tags: vtab-limit-fix)
Changes
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Changes to src/whereexpr.c.

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        if( pExpr->iTable!=iCsr ) return;
        if( pOrderBy->a[ii].fg.sortFlags & KEYINFO_ORDER_BIGNULL ) return;
      }
    }

    /* All conditions are met. Add the terms to the where-clause object. */
    assert( p->pLimit->op==TK_LIMIT );




    if( p->iOffset==0 || (p->selFlags & SF_Compound)==0 ){
      whereAddLimitExpr(pWC, p->iLimit, p->pLimit->pLeft,
                        iCsr, SQLITE_INDEX_CONSTRAINT_LIMIT);
    }
    if( p->iOffset!=0 && (p->selFlags & SF_Compound)==0 ){
      whereAddLimitExpr(pWC, p->iOffset, p->pLimit->pRight,
                        iCsr, SQLITE_INDEX_CONSTRAINT_OFFSET);
    }
  }
}

/*
** Initialize a preallocated WhereClause structure.
*/
void sqlite3WhereClauseInit(








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        if( pExpr->iTable!=iCsr ) return;
        if( pOrderBy->a[ii].fg.sortFlags & KEYINFO_ORDER_BIGNULL ) return;
      }
    }

    /* All conditions are met. Add the terms to the where-clause object. */
    assert( p->pLimit->op==TK_LIMIT );
    if( p->iOffset!=0 && (p->selFlags & SF_Compound)==0 ){
      whereAddLimitExpr(pWC, p->iOffset, p->pLimit->pRight,
                        iCsr, SQLITE_INDEX_CONSTRAINT_OFFSET);
    }
    if( p->iOffset==0 || (p->selFlags & SF_Compound)==0 ){
      whereAddLimitExpr(pWC, p->iLimit, p->pLimit->pLeft,
                        iCsr, SQLITE_INDEX_CONSTRAINT_LIMIT);
    }




  }
}

/*
** Initialize a preallocated WhereClause structure.
*/
void sqlite3WhereClauseInit(
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Changes to test/bestindex8.test.

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  set ::lFilterArgs
} {10}

do_test 2.2 {
  set ::lFilterArgs [list]
  execsql { SELECT * FROM vt1 LIMIT 5 OFFSET 50 }
  set ::lFilterArgs
} {{5 50}}

do_test 2.3 {
  set ::lFilterArgs [list]
  execsql { SELECT * FROM vt1 ORDER BY a, b LIMIT 1 OFFSET 1 }
  set ::lFilterArgs
} {{1 1}}









|








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  set ::lFilterArgs
} {10}

do_test 2.2 {
  set ::lFilterArgs [list]
  execsql { SELECT * FROM vt1 LIMIT 5 OFFSET 50 }
  set ::lFilterArgs
} {{50 5}}

do_test 2.3 {
  set ::lFilterArgs [list]
  execsql { SELECT * FROM vt1 ORDER BY a, b LIMIT 1 OFFSET 1 }
  set ::lFilterArgs
} {{1 1}}
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Changes to test/bestindexC.test.

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      set idxstr [list]
      set res [list]

      set idx 0
      foreach c $clist {
        array set a $c
        if {$a(usable)==0} continue
        if {$a(op)=="limit"} { 
          lappend idxstr limit
          lappend res omit $idx
        }
        if {$a(op)=="offset"} { 
          lappend idxstr offset
          lappend res omit $idx
        }
        incr idx
      }

      return "cost 1000000 rows 1000000 idxnum 0 idxstr {$idxstr} $res"
    }

    xFilter {
      set idxstr [lindex $args 1]
      set LIMIT ""
      foreach a $idxstr b [lindex $args 2] {
        append LIMIT " $a $b"
      }





      set idx 1
      foreach v $lVal {
        lappend lRow "($idx, '$v')"
        incr idx
      }









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      set idxstr [list]
      set res [list]

      set idx 0
      foreach c $clist {
        array set a $c
        if {$a(usable)==0} continue
        if {$a(op)=="limit" && ![info exists ::do_not_use_limit]} { 
          lappend idxstr limit
          lappend res omit $idx
        }
        if {$a(op)=="offset" && ![info exists ::do_not_use_offset]} { 
          lappend idxstr offset
          lappend res omit $idx
        }
        incr idx
      }

      return "cost 1000000 rows 1000000 idxnum 0 idxstr {$idxstr} $res"
    }

    xFilter {
      set idxstr [lindex $args 1]
      set LIMIT ""
      foreach a $idxstr b [lindex $args 2] {
        set x($a) $b
      }

      if {![info exists x(limit)]} { set x(limit) -1 }
      if {![info exists x(offset)]} { set x(offset) -1 }
      set LIMIT " LIMIT $x(limit) OFFSET $x(offset)"

      set idx 1
      foreach v $lVal {
        lappend lRow "($idx, '$v')"
        incr idx
      }
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do_execsql_test 3.3 {
  SELECT * FROM generate_series(1, 5) WHERE value = (value & 14) LIMIT 3
} {2 4}

do_execsql_test 3.4 {
  SELECT value FROM generate_series(1,10) WHERE value>2 LIMIT 4 OFFSET 1;
} {4 5 6 7}














finish_test









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do_execsql_test 3.3 {
  SELECT * FROM generate_series(1, 5) WHERE value = (value & 14) LIMIT 3
} {2 4}

do_execsql_test 3.4 {
  SELECT value FROM generate_series(1,10) WHERE value>2 LIMIT 4 OFFSET 1;
} {4 5 6 7}

set ::do_not_use_limit 1
do_execsql_test 3.5 {
  SELECT * FROM y1 LIMIT 5 OFFSET 3
} {4 5 6 7 8}
unset ::do_not_use_limit
set ::do_not_use_offset 1
do_execsql_test 3.6 {
  SELECT * FROM y1 LIMIT 5 OFFSET 3
} {4 5 6 7 8}
unset ::do_not_use_offset



finish_test