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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Within a loop that uses a non-covering index test, test non-indexed terms that can be tested without seeking the main table cursor before those that cannot.
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SHA3-256: afe68f0a8060dc5c92cb1fb32a9f22bd36140cd2c0bb5b6cea853e169c5ed444
User & Date: dan 2017-04-28 19:59:55
Context
2017-04-29
14:56
Minor size and performance improvements to the push-down optimization. Closed-Leaf check-in: 91dfb61a user: drh tags: pushdown-optimization
2017-04-28
19:59
Within a loop that uses a non-covering index test, test non-indexed terms that can be tested without seeking the main table cursor before those that cannot. check-in: afe68f0a user: dan tags: pushdown-optimization
2017-04-26
17:21
Add new test file cachespill.test. check-in: 2d0b6431 user: dan tags: trunk
Changes
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Changes to src/wherecode.c.

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  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;                    /* Jump here to break out of the loop */
  int addrHalt;                   /* addrBrk for the outermost loop */
  int addrCont;                   /* Jump here to continue with next cycle */
  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
  int iReleaseReg = 0;      /* Temp register to free before returning */


  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = &pWInfo->sWC;
  db = pParse->db;
  pLevel = &pWInfo->a[iLevel];
  pLoop = pLevel->pWLoop;
................................................................................
    int regBase;                 /* Base register holding constraint values */
    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
    int startEq;                 /* True if range start uses ==, >= or <= */
    int endEq;                   /* True if range end uses ==, >= or <= */
    int start_constraints;       /* Start of range is constrained */
    int nConstraint;             /* Number of constraint terms */
    Index *pIdx;                 /* The index we will be using */
    int iIdxCur;                 /* The VDBE cursor for the index */
    int nExtraReg = 0;           /* Number of extra registers needed */
    int op;                      /* Instruction opcode */
    char *zStartAff;             /* Affinity for start of range constraint */
    char *zEndAff = 0;           /* Affinity for end of range constraint */
    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
................................................................................
    pLevel->p1 = iIdxCur;
    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }else{
      assert( pLevel->p5==0 );
    }

  }else

#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  if( pLoop->wsFlags & WHERE_MULTI_OR ){
    /* Case 5:  Two or more separately indexed terms connected by OR
    **
    ** Example:
................................................................................

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
#endif

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  */





  for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
    Expr *pE;
    int skipLikeAddr = 0;
    testcase( pTerm->wtFlags & TERM_VIRTUAL );
    testcase( pTerm->wtFlags & TERM_CODED );
    if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
    if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
      testcase( pWInfo->untestedTerms==0
               && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)!=0 );
      pWInfo->untestedTerms = 1;
      continue;
    }
    pE = pTerm->pExpr;
    assert( pE!=0 );



    if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
      continue;
    }
    if( pTerm->wtFlags & TERM_LIKECOND ){
      /* If the TERM_LIKECOND flag is set, that means that the range search
      ** is sufficient to guarantee that the LIKE operator is true, so we
      ** can skip the call to the like(A,B) function.  But this only works
      ** for strings.  So do not skip the call to the function on the pass
      ** that compares BLOBs. */
#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
      continue;
#else
      u32 x = pLevel->iLikeRepCntr;
      assert( x>0 );
      skipLikeAddr = sqlite3VdbeAddOp1(v, (x&1)? OP_IfNot : OP_If, (int)(x>>1));
      VdbeCoverage(v);
#endif
    }
    sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
    if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
    pTerm->wtFlags |= TERM_CODED;



  }

  /* Insert code to test for implied constraints based on transitivity
  ** of the "==" operator.
  **
  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
  ** and we are coding the t1 loop and the t2 loop has not yet coded,







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  Vdbe *v;                        /* The prepared stmt under constructions */
  struct SrcList_item *pTabItem;  /* FROM clause term being coded */
  int addrBrk;                    /* Jump here to break out of the loop */
  int addrHalt;                   /* addrBrk for the outermost loop */
  int addrCont;                   /* Jump here to continue with next cycle */
  int iRowidReg = 0;        /* Rowid is stored in this register, if not zero */
  int iReleaseReg = 0;      /* Temp register to free before returning */
  Index *pIdx = 0;          /* Index used by loop (if any) */

  pParse = pWInfo->pParse;
  v = pParse->pVdbe;
  pWC = &pWInfo->sWC;
  db = pParse->db;
  pLevel = &pWInfo->a[iLevel];
  pLoop = pLevel->pWLoop;
................................................................................
    int regBase;                 /* Base register holding constraint values */
    WhereTerm *pRangeStart = 0;  /* Inequality constraint at range start */
    WhereTerm *pRangeEnd = 0;    /* Inequality constraint at range end */
    int startEq;                 /* True if range start uses ==, >= or <= */
    int endEq;                   /* True if range end uses ==, >= or <= */
    int start_constraints;       /* Start of range is constrained */
    int nConstraint;             /* Number of constraint terms */

    int iIdxCur;                 /* The VDBE cursor for the index */
    int nExtraReg = 0;           /* Number of extra registers needed */
    int op;                      /* Instruction opcode */
    char *zStartAff;             /* Affinity for start of range constraint */
    char *zEndAff = 0;           /* Affinity for end of range constraint */
    u8 bSeekPastNull = 0;        /* True to seek past initial nulls */
    u8 bStopAtNull = 0;          /* Add condition to terminate at NULLs */
................................................................................
    pLevel->p1 = iIdxCur;
    pLevel->p3 = (pLoop->wsFlags&WHERE_UNQ_WANTED)!=0 ? 1:0;
    if( (pLoop->wsFlags & WHERE_CONSTRAINT)==0 ){
      pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
    }else{
      assert( pLevel->p5==0 );
    }
    if( omitTable ) pIdx = 0;
  }else

#ifndef SQLITE_OMIT_OR_OPTIMIZATION
  if( pLoop->wsFlags & WHERE_MULTI_OR ){
    /* Case 5:  Two or more separately indexed terms connected by OR
    **
    ** Example:
................................................................................

#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
  pLevel->addrVisit = sqlite3VdbeCurrentAddr(v);
#endif

  /* Insert code to test every subexpression that can be completely
  ** computed using the current set of tables.
  **
  ** This loop may run either once (pIdx==0) or twice (pIdx!=0). If
  ** it is run twice, then the first iteration codes those sub-expressions
  ** that can be computed using columns from pIdx only (without seeking
  ** the main table cursor).  */
  while( 1 ){
    for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
      Expr *pE;
      int skipLikeAddr = 0;
      testcase( pTerm->wtFlags & TERM_VIRTUAL );
      testcase( pTerm->wtFlags & TERM_CODED );
      if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
      if( (pTerm->prereqAll & pLevel->notReady)!=0 ){
        testcase( pWInfo->untestedTerms==0
            && (pWInfo->wctrlFlags & WHERE_OR_SUBCLAUSE)!=0 );
        pWInfo->untestedTerms = 1;
        continue;
      }
      pE = pTerm->pExpr;
      assert( pE!=0 );
      if( pIdx && !sqlite3ExprCoveredByIndex(pE, pLevel->iTabCur, pIdx) ){
        continue;
      }
      if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
        continue;
      }
      if( pTerm->wtFlags & TERM_LIKECOND ){
        /* If the TERM_LIKECOND flag is set, that means that the range search
        ** is sufficient to guarantee that the LIKE operator is true, so we
        ** can skip the call to the like(A,B) function.  But this only works
        ** for strings.  So do not skip the call to the function on the pass
        ** that compares BLOBs. */
#ifdef SQLITE_LIKE_DOESNT_MATCH_BLOBS
        continue;
#else
        u32 x = pLevel->iLikeRepCntr;
        assert( x>0 );
        skipLikeAddr = sqlite3VdbeAddOp1(v, (x&1)?OP_IfNot:OP_If, (int)(x>>1));
        VdbeCoverage(v);
#endif
      }
      sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
      if( skipLikeAddr ) sqlite3VdbeJumpHere(v, skipLikeAddr);
      pTerm->wtFlags |= TERM_CODED;
    }
    if( pIdx==0 ) break;
    pIdx = 0;
  }

  /* Insert code to test for implied constraints based on transitivity
  ** of the "==" operator.
  **
  ** Example: If the WHERE clause contains "t1.a=t2.b" and "t2.b=123"
  ** and we are coding the t1 loop and the t2 loop has not yet coded,

Added test/pushdown.test.























































































































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# 2017 April 29
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************

set testdir [file dirname $argv0]
source $testdir/tester.tcl
set testprefix pushdown

do_execsql_test 1.0 {
  CREATE TABLE t1(a, b, c);
  INSERT INTO t1 VALUES(1, 'b1', 'c1');
  INSERT INTO t1 VALUES(2, 'b2', 'c2');
  INSERT INTO t1 VALUES(3, 'b3', 'c3');
  INSERT INTO t1 VALUES(4, 'b4', 'c4');
  CREATE INDEX i1 ON t1(a, c);
}

proc f {val} {
  lappend ::L $val
  return 0
}
db func f f 

do_test 1.1 {
  set L [list]
  execsql { SELECT * FROM t1 WHERE a=2 AND f(b) AND f(c) }
  set L
} {c2}

do_test 1.2 {
  set L [list]
  execsql { SELECT * FROM t1 WHERE a=3 AND f(c) AND f(b) }
  set L
} {c3}

do_execsql_test 1.3 {
  DROP INDEX i1;
  CREATE INDEX i1 ON t1(a, b);
}
do_test 1.4 {
  set L [list]
  execsql { SELECT * FROM t1 WHERE a=2 AND f(b) AND f(c) }
  set L
} {b2}

do_test 1.5 {
  set L [list]
  execsql { SELECT * FROM t1 WHERE a=3 AND f(c) AND f(b) }
  set L
} {b3}
  
finish_test