Documentation updates. (CVS 2726)
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C ON-clause\sterms\sin\sa\sLEFT\sJOIN\sthat\srestrict\sonly\sthe\sleft\stable,\sshould\snot\nreally\srestrict\sthe\sleft\stable\sbut\sinstead\srows\sthat\sfail\sto\smeet\sthe\scondition\nto\sbe\sjoined\swith\sNULL\srows\sfrom\sthe\sright\stable.\s(CVS\s2725)
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D 2005-09-19T21:05:49
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C Documentation\supdates.\s(CVS\s2726)
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D 2005-09-20T01:36:30
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F Makefile.in 12784cdce5ffc8dfb707300c34e4f1eb3b8a14f1
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F Makefile.linux-gcc 06be33b2a9ad4f005a5f42b22c4a19dab3cbb5c7
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F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
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@ -300,7 +300,7 @@ F www/omitted.tcl 658ebdc83781ac419dc8a08b3f6cf93929023470
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F www/opcode.tcl 5bd68059416b223515a680d410a9f7cb6736485f
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F www/optimizer.tcl d6812a10269bd0d7c488987aac0ad5036cace9dc
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F www/optimizing.tcl f0b2538988d1bbad16cbfe63ec6e8f48c9eb04e5
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F www/optoverview.tcl 5ff8a1c38722fa9f5cb3e1b8010f6b91c5a45693
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F www/optoverview.tcl 28b6f114a33bfd91bbe3440611ceed6090587211
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F www/pragma.tcl 44f7b665ca598ad24724f35991653638a36a6e3f
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F www/quickstart.tcl 6f6f694b6139be2d967b1492eb9a6bdf7058aa60
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F www/speed.tcl 656ed5be8cc9d536353e1a96927b925634a62933
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@ -311,7 +311,7 @@ F www/tclsqlite.tcl ddcf912ea48695603c8ed7efb29f0812ef8d1b49
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F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
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F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
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F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
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P b32e9ec2480f9da2c2ea705ed3c88ca77b77cf2a
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R 30beedb46fba1ce2f76a3f1396f53cb5
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P ea10f9785e3c5248dafcc297f3a2c5465b6e0dba
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R 6ad171a801eb8b84ac88c34ad2f04d27
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U drh
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Z a986dad9151bb581e7854782adc6d5e8
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Z 23a34f97623654d558cd9b041aa96deb
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@ -1 +1 @@
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ea10f9785e3c5248dafcc297f3a2c5465b6e0dba
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6ec8883c366532948e619830ff7d9f63b79fc08b
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@ -1,7 +1,7 @@
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#
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# Run this TCL script to generate HTML for the goals.html file.
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#
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set rcsid {$Id: optoverview.tcl,v 1.3 2005/08/31 13:48:35 drh Exp $}
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set rcsid {$Id: optoverview.tcl,v 1.4 2005/09/20 01:36:30 drh Exp $}
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source common.tcl
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header {The SQLite Query Optimizer Overview}
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@ -25,8 +25,8 @@ proc IMAGE {name {caption {}}} {
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puts "</center>"
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}
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proc PARAGRAPH {text} {
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regsub -all "/(\[^\n/\]+)/" $text {<i>\1</i>} t2
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regsub -all "\\*(\[^\n*\]+)\\*" $t2 {<tt><b><big>\1</big></b></tt>} t3
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# regsub -all "/(\[a-zA-Z0-9\]+)/" $text {<i>\1</i>} t2
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regsub -all "\\*(\[^\n*\]+)\\*" $text {<tt><b><big>\1</big></b></tt>} t3
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puts "<p>$t3</p>\n"
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}
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set level(0) 0
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@ -165,7 +165,7 @@ PARAGRAPH {
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virtual terms themselves never causes tests to be performed on
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input rows.
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Thus if the BETWEEN term is not used as an index constraint and
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instead must be used to test input rows, the /expr1/ expression is
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instead must be used to test input rows, the <i>expr1</i> expression is
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only evaluated once.
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}
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@ -187,7 +187,7 @@ SYNTAX {
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PARAGRAPH {
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The rewritten term then might go on to constraint an index using the
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normal rules for *IN* operators.
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Note that /column/ must be the same column in every OR-connected subterm,
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Note that <i>column</i> must be the same column in every OR-connected subterm,
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although the column can occur on either the left or the right side of
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the *=* operator.
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}
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@ -271,12 +271,12 @@ PARAGRAPH {
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}
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PARAGRAPH {
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Suppose the initial sequence of non-wildcard characters on the right-hand
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side of the LIKE or GLOB operator is /x/. We are using a single
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side of the LIKE or GLOB operator is <i>x</i>. We are using a single
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character to denote this non-wildcard prefix but the reader should
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understand that the prefix can consist of more than 1 character.
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Let /y/ the smallest string that is the same length as /x/ but which
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compares greater than /x/. For example, if /x/ is *hello* then
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/y/ would be *hellp*.
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Let <i>y</i> the smallest string that is the same length as /x/ but which
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compares greater than <i>x</i>. For example, if <i>x</i> is *hello* then
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<i>y</i> would be *hellp*.
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The LIKE and GLOB optimizations consist of adding two virtual terms
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like this:
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}
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@ -288,8 +288,8 @@ PARAGRAPH {
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tested against each input row even if the virtual terms are used to
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constrain an index. This is because we do not know what additional
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constraints may be imposed by characters to the right
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of the /x/ prefix. However, if there is only a single global wildcard
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to the right of /x/, then the original LIKE or GLOB test is disabled.
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of the <i>x</i> prefix. However, if there is only a single global wildcard
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to the right of <i>x</i>, then the original LIKE or GLOB test is disabled.
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In other words, if the pattern is like this:
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}
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SYNTAX {
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@ -335,6 +335,14 @@ PARAGRAPH {
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over the older SQL89 comma-join syntax. They both end up accomplishing
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exactly the same thing.
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}
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PARAGRAPH {
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Join reordering is automatic and usually works well enough that
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programmer do not have to think about it. But occasionally some
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hints from the programmer are needed. For a description of when
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hints might be necessary and how to provide those hints, see the
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<a href="http://www.sqlite.org/cvstrac/wiki?p=QueryPlans">QueryPlans</a>
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page in the Wiki.
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}
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HEADING 1 {Choosing between multiple indices} multi_index
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