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Improvements to cost estimation for evaluating the IN operator.
Ticket #3757. (CVS 6403) FossilOrigin-Name: 0c438e813c411e8f9e92d6c7405fccb7a36e110a
This commit is contained in:
drh
13
manifest
13
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@@ -1,5 +1,5 @@
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C Previous\scommit\s((6401))\sdid\snot\squite\sfix\sthe\sproblem.\s\sThis\sshould\swork\nbetter.\s(CVS\s6402)
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D 2009-03-28T23:47:11
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C Improvements\sto\scost\sestimation\sfor\sevaluating\sthe\sIN\soperator.\nTicket\s#3757.\s(CVS\s6403)
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D 2009-03-29T00:13:03
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F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
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F Makefile.in 583e87706abc3026960ed759aff6371faf84c211
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F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
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@@ -209,7 +209,7 @@ F src/vdbeblob.c e67757450ae8581a8b354d9d7e467e41502dfe38
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F src/vdbemem.c 38615b5d4b1b3b5a1221a5623578e5e3864e4888
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F src/vtab.c f1aba5a6dc1f83b97a39fbbc58ff8cbc76311347
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F src/walker.c 42bd3f00ca2ef5ae842304ec0d59903ef051412d
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F src/where.c d0a78f876593b596c1e97286921cdc746e2f65ce
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F src/where.c 72b84f31a0bed42c665fb922b74e9aea5ae3ced2
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F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
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F test/alias.test 597662c5d777a122f9a3df0047ea5c5bd383a911
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F test/all.test 14165b3e32715b700b5f0cbf8f6e3833dda0be45
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@@ -631,6 +631,7 @@ F test/tkt35xx.test 53bca895091e968126a858ee7da186f59f328994
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F test/tkt3630.test 929f64852103054125200bc825c316d5f75d42f7
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F test/tkt3718.test 3ee5e25702f3f5a31340b2766d7a7fac2b5ce99c
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F test/tkt3731.test 8a6e3732f5a8a24eb875a6faf287ef77bb8c0579
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F test/tkt3757.test 8f2208930655bbd4f92c14e19e72303a43e098ef
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F test/tokenize.test ce430a7aed48fc98301611429595883fdfcab5d7
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F test/trace.test 951cd0f5f571e7f36bf7bfe04be70f90fb16fb00
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F test/trans.test 8b79967a7e085289ec64890c6fdf9d089e1b4a5f
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@@ -710,7 +711,7 @@ F tool/speedtest16.c c8a9c793df96db7e4933f0852abb7a03d48f2e81
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F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
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F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
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F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
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P fb35cff855e17771caee2a992e7b2b4105b94862
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R 6c5a32ed1dbda923c028324f6e381112
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P 2e7d3cc9f04de1fe7ef95cd5736dbc409c209cef
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R f4372d788a5fa3a6a07058dbb62c2eb3
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U drh
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Z f8f9e15c31b81a3e0355740fc1bcee00
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Z 1bf6a0cf4ef6100a42ff75750d967094
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@@ -1 +1 @@
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2e7d3cc9f04de1fe7ef95cd5736dbc409c209cef
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0c438e813c411e8f9e92d6c7405fccb7a36e110a
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33
src/where.c
33
src/where.c
@@ -16,7 +16,7 @@
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** so is applicable. Because this module is responsible for selecting
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** indices, you might also think of this module as the "query optimizer".
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**
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** $Id: where.c,v 1.377 2009/03/25 16:51:43 drh Exp $
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** $Id: where.c,v 1.378 2009/03/29 00:13:03 drh Exp $
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*/
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#include "sqliteInt.h"
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@@ -26,7 +26,7 @@
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#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
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int sqlite3WhereTrace = 0;
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#endif
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#if 0
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#if 1
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# define WHERETRACE(X) if(sqlite3WhereTrace) sqlite3DebugPrintf X
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#else
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# define WHERETRACE(X)
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@@ -1926,12 +1926,18 @@ static void bestIndex(
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pProbe = pSrc->pIndex;
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}
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for(; pProbe; pProbe=(pSrc->pIndex ? 0 : pProbe->pNext)){
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double inMultiplier = 1;
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double inMultiplier = 1; /* Number of equality look-ups needed */
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int inMultIsEst = 0; /* True if inMultiplier is an estimate */
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WHERETRACE(("... index %s:\n", pProbe->zName));
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/* Count the number of columns in the index that are satisfied
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** by x=EXPR constraints or x IN (...) constraints.
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** by x=EXPR constraints or x IN (...) constraints. For a term
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** of the form x=EXPR we only have to do a single binary search.
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** But for x IN (...) we have to do a number of binary searched
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** equal to the number of entries on the RHS of the IN operator.
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** The inMultipler variable with try to estimate the number of
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** binary searches needed.
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*/
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wsFlags = 0;
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for(i=0; i<pProbe->nColumn; i++){
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@@ -1944,21 +1950,31 @@ static void bestIndex(
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wsFlags |= WHERE_COLUMN_IN;
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if( ExprHasProperty(pExpr, EP_xIsSelect) ){
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inMultiplier *= 25;
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inMultIsEst = 1;
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}else if( pExpr->x.pList ){
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inMultiplier *= pExpr->x.pList->nExpr + 1;
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}
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}
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}
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nRow = pProbe->aiRowEst[i] * inMultiplier;
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cost = nRow * estLog(inMultiplier);
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/* If inMultiplier is an estimate and that estimate results in an
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** nRow it that is more than half number of rows in the table,
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** then reduce inMultipler */
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if( inMultIsEst && nRow*2 > pProbe->aiRowEst[0] ){
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nRow = pProbe->aiRowEst[0]/2;
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inMultiplier = nRow/pProbe->aiRowEst[i];
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}
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cost = nRow + inMultiplier*estLog(pProbe->aiRowEst[0]);
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nEq = i;
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if( pProbe->onError!=OE_None && (wsFlags & WHERE_COLUMN_IN)==0
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&& nEq==pProbe->nColumn ){
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wsFlags |= WHERE_UNIQUE;
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}
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WHERETRACE(("...... nEq=%d inMult=%.9g cost=%.9g\n",nEq,inMultiplier,cost));
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WHERETRACE(("...... nEq=%d inMult=%.9g nRow=%.9g cost=%.9g\n",
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nEq, inMultiplier, nRow, cost));
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/* Look for range constraints
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/* Look for range constraints. Assume that each range constraint
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** makes the search space 1/3rd smaller.
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*/
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if( nEq<pProbe->nColumn ){
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int j = pProbe->aiColumn[nEq];
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@@ -1975,7 +1991,8 @@ static void bestIndex(
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cost /= 3;
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nRow /= 3;
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}
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WHERETRACE(("...... range reduces cost to %.9g\n", cost));
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WHERETRACE(("...... range reduces nRow to %.9g and cost to %.9g\n",
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nRow, cost));
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}
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}
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60
test/tkt3757.test
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60
test/tkt3757.test
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# 2009 March 28
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#
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# The author disclaims copyright to this source code. In place of
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# a legal notice, here is a blessing:
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#
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# May you do good and not evil.
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# May you find forgiveness for yourself and forgive others.
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# May you share freely, never taking more than you give.
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#
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#***********************************************************************
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#
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# Ticket #3757: The cost functions on the query optimizer for the
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# IN operator can be improved.
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#
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# $Id: tkt3757.test,v 1.1 2009/03/29 00:13:04 drh Exp $
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set testdir [file dirname $argv0]
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source $testdir/tester.tcl
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# Evaluate SQL. Return the result set followed by the
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# and the number of full-scan steps.
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#
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proc count_steps {sql} {
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set r [db eval $sql]
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lappend r scan [db status step] sort [db status sort]
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}
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# Construct tables
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#
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do_test tkt3757-1.1 {
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db eval {
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CREATE TABLE t1(x INTEGER, y INTEGER, z TEXT);
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CREATE INDEX t1i1 ON t1(y,z);
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INSERT INTO t1 VALUES(1,2,'three');
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CREATE TABLE t2(a INTEGER, b TEXT);
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INSERT INTO t2 VALUES(2, 'two');
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ANALYZE;
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SELECT * FROM sqlite_stat1;
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}
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} {t1 t1i1 {1 1 1}}
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# Modify statistics in order to make the optimizer then that:
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#
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# (1) Table T1 has about 250K entries
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# (2) There are only about 5 distinct values of T1.
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#
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# Then run a query with "t1.y IN (SELECT ..)" in the WHERE clause.
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# Make sure the index is used.
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#
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do_test tkt3757-1.2 {
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db eval {
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DELETE FROM sqlite_stat1;
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INSERT INTO sqlite_stat1 VALUES('t1','t1i1','250000 50000 30');
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}
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count_steps {
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SELECT * FROM t1 WHERE y IN (SELECT a FROM t2)
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}
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} {1 2 three scan 0 sort 0}
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finish_test
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