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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Undo some unhelpful changes to skip-scan scoring that were added by the check-in [9e2b2681] that improved scoring of index scan.
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SHA1: c7d51934a4f30d096bb79fc509fc9dd0df5d89a4
User & Date: drh 2016-07-29 01:32:36
Context
2016-07-29
01:49
Further refinement to the calling convention macros. check-in: 45588de3 user: drh tags: trunk
01:47
Merge updates from trunk. check-in: 71ffa195 user: mistachkin tags: callbackConv
01:32
Undo some unhelpful changes to skip-scan scoring that were added by the check-in [9e2b2681] that improved scoring of index scan. check-in: c7d51934 user: drh tags: trunk
2016-07-28
19:28
The 'sqlite3ext.h' content should be processed before being included in the amalgamation. check-in: cbe1de47 user: mistachkin tags: trunk
Changes
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Changes to src/where.c.

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   && (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
  ){
    LogEst nIter;
    pNew->u.btree.nEq++;
    pNew->nSkip++;
    pNew->aLTerm[pNew->nLTerm++] = 0;
    pNew->wsFlags |= WHERE_SKIPSCAN;
    nIter = pProbe->aiRowLogEst[saved_nEq]+1 - pProbe->aiRowLogEst[saved_nEq+1];
    pNew->nOut -= nIter;
    /* TUNING:  Because uncertainties in the estimates for skip-scan queries,
    ** add a 1.375 fudge factor to make skip-scan slightly less likely. */
    nIter += 4;
    whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul);
    pNew->nOut = saved_nOut;
    pNew->u.btree.nEq = saved_nEq;
    pNew->nSkip = saved_nSkip;
    pNew->wsFlags = saved_wsFlags;
  }








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   && (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
  ){
    LogEst nIter;
    pNew->u.btree.nEq++;
    pNew->nSkip++;
    pNew->aLTerm[pNew->nLTerm++] = 0;
    pNew->wsFlags |= WHERE_SKIPSCAN;
    nIter = pProbe->aiRowLogEst[saved_nEq] - pProbe->aiRowLogEst[saved_nEq+1];
    pNew->nOut -= nIter;
    /* TUNING:  Because uncertainties in the estimates for skip-scan queries,
    ** add a 1.375 fudge factor to make skip-scan slightly less likely. */
    nIter += 5;
    whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul);
    pNew->nOut = saved_nOut;
    pNew->u.btree.nEq = saved_nEq;
    pNew->nSkip = saved_nSkip;
    pNew->wsFlags = saved_wsFlags;
  }

Changes to test/scanstatus.test.

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do_eqp_test 5.3.1 {
  SELECT count(*) FROM t2 WHERE y = 'j';
} {0 0 0 {SEARCH TABLE t2 USING COVERING INDEX t2xy (ANY(x) AND y=?)}}
do_execsql_test 5.3.2 {
  SELECT count(*) FROM t2 WHERE y = 'j';
} {19}
do_scanstatus_test 5.3.3 { 
  nLoop 1 nVisit 19 nEst 52.0 zName t2xy zExplain
  {SEARCH TABLE t2 USING COVERING INDEX t2xy (ANY(x) AND y=?)}
}

do_eqp_test 5.4.1 {
  SELECT count(*) FROM t1, t2 WHERE y = c;
} {
  0 0 0 {SCAN TABLE t1 USING COVERING INDEX t1bc}
................................................................................
}
do_execsql_test 5.4.2 {
  SELECT count(*) FROM t1, t2 WHERE y = c;
} {200}
do_scanstatus_test 5.4.3 { 
  nLoop 1 nVisit 10 nEst 10.0 zName t1bc 
  zExplain {SCAN TABLE t1 USING COVERING INDEX t1bc}
  nLoop 10 nVisit 200 nEst 52.0 zName t2xy 
  zExplain {SEARCH TABLE t2 USING COVERING INDEX t2xy (ANY(x) AND y=?)}
}

do_eqp_test 5.5.1 {
  SELECT count(*) FROM t1, t3 WHERE y = c;
} {
  0 0 1 {SCAN TABLE t3} 







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do_eqp_test 5.3.1 {
  SELECT count(*) FROM t2 WHERE y = 'j';
} {0 0 0 {SEARCH TABLE t2 USING COVERING INDEX t2xy (ANY(x) AND y=?)}}
do_execsql_test 5.3.2 {
  SELECT count(*) FROM t2 WHERE y = 'j';
} {19}
do_scanstatus_test 5.3.3 { 
  nLoop 1 nVisit 19 nEst 56.0 zName t2xy zExplain
  {SEARCH TABLE t2 USING COVERING INDEX t2xy (ANY(x) AND y=?)}
}

do_eqp_test 5.4.1 {
  SELECT count(*) FROM t1, t2 WHERE y = c;
} {
  0 0 0 {SCAN TABLE t1 USING COVERING INDEX t1bc}
................................................................................
}
do_execsql_test 5.4.2 {
  SELECT count(*) FROM t1, t2 WHERE y = c;
} {200}
do_scanstatus_test 5.4.3 { 
  nLoop 1 nVisit 10 nEst 10.0 zName t1bc 
  zExplain {SCAN TABLE t1 USING COVERING INDEX t1bc}
  nLoop 10 nVisit 200 nEst 56.0 zName t2xy 
  zExplain {SEARCH TABLE t2 USING COVERING INDEX t2xy (ANY(x) AND y=?)}
}

do_eqp_test 5.5.1 {
  SELECT count(*) FROM t1, t3 WHERE y = c;
} {
  0 0 1 {SCAN TABLE t3} 

Changes to test/skipscan1.test.

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# index unconstrainted.
#
do_execsql_test skipscan1-1.2 {
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-1.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {/* USING INDEX t1abc (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-1.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.3 {
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a DESC;
} {def 345 9 10 | abc 345 7 8 |}
do_execsql_test skipscan1-1.3eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {/* USING INDEX t1abc (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-1.3sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.4 {
  SELECT a,b,c,d,'|' FROM t1 WHERE c=6 ORDER BY a, b, c;
} {abc 234 6 7 | bcd 100 6 11 |}
do_execsql_test skipscan1-1.4eqp {
  EXPLAIN QUERY PLAN
................................................................................
  ** columns are not selective. */
  ANALYZE;
  UPDATE sqlite_stat1 SET stat='10000 5000 2000 10' WHERE idx NOT NULL;
  ANALYZE sqlite_master;
} {}

do_execsql_test skipscan1-2.2 {
  SELECT a,b,c,d,'|' FROM t2 WHERE b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-2.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t2 WHERE b=345 ORDER BY a;
} {/* USING INDEX sqlite_autoindex_t2_1 (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-2.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t2 WHERE b=345 ORDER BY a;
} {~/*ORDER BY*/}


do_execsql_test skipscan1-3.1 {
  CREATE TABLE t3(a TEXT, b INT, c INT, d INT,
                  PRIMARY KEY(a,b,c)) WITHOUT ROWID;
  INSERT INTO t3 SELECT * FROM t1;







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# index unconstrainted.
#
do_execsql_test skipscan1-1.2 {
  SELECT a,b,c,d,'|' FROM t1 WHERE b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-1.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a;
} {/* USING INDEX t1abc (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-1.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.3 {
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a DESC;
} {def 345 9 10 | abc 345 7 8 |}
do_execsql_test skipscan1-1.3eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a DESC;
} {/* USING INDEX t1abc (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-1.3sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t1 WHERE d<>99 AND b=345 ORDER BY a DESC;
} {~/*ORDER BY*/}

do_execsql_test skipscan1-1.4 {
  SELECT a,b,c,d,'|' FROM t1 WHERE c=6 ORDER BY a, b, c;
} {abc 234 6 7 | bcd 100 6 11 |}
do_execsql_test skipscan1-1.4eqp {
  EXPLAIN QUERY PLAN
................................................................................
  ** columns are not selective. */
  ANALYZE;
  UPDATE sqlite_stat1 SET stat='10000 5000 2000 10' WHERE idx NOT NULL;
  ANALYZE sqlite_master;
} {}

do_execsql_test skipscan1-2.2 {
  SELECT a,b,c,d,'|' FROM t2 WHERE d<>99 AND b=345 ORDER BY a;
} {abc 345 7 8 | def 345 9 10 |}
do_execsql_test skipscan1-2.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t2 WHERE d<>99 AND b=345 ORDER BY a;
} {/* USING INDEX sqlite_autoindex_t2_1 (ANY(a) AND b=?)*/}
do_execsql_test skipscan1-2.2sort {
  EXPLAIN QUERY PLAN
  SELECT a,b,c,d,'|' FROM t2 WHERE d<>99 AND b=345 ORDER BY a;
} {~/*ORDER BY*/}


do_execsql_test skipscan1-3.1 {
  CREATE TABLE t3(a TEXT, b INT, c INT, d INT,
                  PRIMARY KEY(a,b,c)) WITHOUT ROWID;
  INSERT INTO t3 SELECT * FROM t1;