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Improvements to comments. No code changes. (CVS 618)

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FossilOrigin-Name: 7e10e60bb78b680bb822908a0b7763f8f5e3ee5a
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drh
2002-06-14 20:58:45 +00:00
parent c67980bedc
commit c27a1ce4bd
4 changed files with 97 additions and 29 deletions
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14
manifest
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@@ -1,5 +1,5 @@
C Fix\sfor\sbug\s#72:\sMake\ssure\sthe\sfile\sdescriptors\sare\sproperly\sclosed\sif\nsqliteInit()\sfails\sfor\sany\sreason.\s(CVS\s617)
D 2002-06-14T20:54:15
C Improvements\sto\scomments.\s\sNo\scode\schanges.\s(CVS\s618)
D 2002-06-14T20:58:45
F Makefile.in 6291a33b87d2a395aafd7646ee1ed562c6f2c28c
F Makefile.template 4e11752e0b5c7a043ca50af4296ec562857ba495
F README a4c0ba11354ef6ba0776b400d057c59da47a4cc0
@@ -51,10 +51,10 @@ F src/threadtest.c 81f0598e0f031c1bd506af337fdc1b7e8dff263f
F src/tokenize.c 890ca022d45f1798dadc300a798951597428853e
F src/trigger.c 21342af6ac031fece39c8fc6eabd1739ca5327c1
F src/update.c 05431e23a9c83502fd7911e771c8366fc2b90b4c
F src/util.c 7cf46b5612f5d12601c697374b9c6b38b2332ce8
F src/util.c 876b259f9186e84b944b72e793dd3dad50e63e95
F src/vdbe.c 836f2c4f823c94c3c3454125d9ba9283e8b22dda
F src/vdbe.h 1742d6f8b40f40879475b4c41cf4f9980ceb0e21
F src/where.c b7c653054d4941d17f3112776ebcaf00d9613cb7
F src/where.c bd25559800ba1fbe1fd596eaec14c417aa1e1b46
F test/all.test e4d3821eeba751829b419cd47814bd20af4286d1
F test/bigrow.test 8ab252dba108f12ad64e337b0f2ff31a807ac578
F test/btree.test bf326f546a666617367a7033fa2c07451bd4f8e1
@@ -137,7 +137,7 @@ F www/speed.tcl da8afcc1d3ccc5696cfb388a68982bc3d9f7f00f
F www/sqlite.tcl 8b5884354cb615049aed83039f8dfe1552a44279
F www/tclsqlite.tcl 1db15abeb446aad0caf0b95b8b9579720e4ea331
F www/vdbe.tcl 2013852c27a02a091d39a766bc87cff329f21218
P 3387d5b6d62fbafea69fac7bb8256c37d5c6a4ba
R 55f4a18ed8c64842b0e836d93bcc263f
P e67ac0fec51788aca0429d04310f86c9c1cf9d13
R c5c72185b42e3894c8a67dc4dc44e497
U drh
Z 3504b88b5175db600e1d0221cbd874dc
Z ec1b6ad2227bde141b128cfba4f6e91b

2
manifest.uuid
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@@ -1 +1 @@
e67ac0fec51788aca0429d04310f86c9c1cf9d13
7e10e60bb78b680bb822908a0b7763f8f5e3ee5a

4
src/util.c
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@@ -14,7 +14,7 @@
** This file contains functions for allocating memory, comparing
** strings, and stuff like that.
**
** $Id: util.c,v 1.45 2002/05/31 15:51:25 drh Exp $
** $Id: util.c,v 1.46 2002/06/14 20:58:45 drh Exp $
*/
#include "sqliteInt.h"
#include <stdarg.h>
@@ -1084,7 +1084,7 @@ sqliteLikeCompare(const unsigned char *zPattern, const unsigned char *zString){
** same sqlite* pointer at the same time. There is a race
** condition so it is possible that the error is not detected.
** But usually the problem will be seen. The result will be an
** error which can be used to debugging the application that is
** error which can be used to debug the application that is
** using SQLite incorrectly.
*/
int sqliteSafetyOn(sqlite *db){

106
src/where.c
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@@ -13,7 +13,7 @@
** the WHERE clause of SQL statements. Also found here are subroutines
** to generate VDBE code to evaluate expressions.
**
** $Id: where.c,v 1.50 2002/06/09 01:55:20 drh Exp $
** $Id: where.c,v 1.51 2002/06/14 20:58:45 drh Exp $
*/
#include "sqliteInt.h"
@@ -103,7 +103,7 @@ static int exprTableUsage(int base, Expr *p){
/*
** Return TRUE if the given operator is one of the operators that is
** allowed for an indexable WHERE clause. The allowed operators are
** "=", "<", ">", "<=", and ">=".
** "=", "<", ">", "<=", ">=", and "IN".
*/
static int allowedOp(int op){
switch( op ){
@@ -156,6 +156,58 @@ static void exprAnalyze(int base, ExprInfo *pInfo){
** in order to complete the WHERE clause processing.
**
** If an error occurs, this routine returns NULL.
**
** The basic idea is to do a nested loop, one loop for each table in
** the FROM clause of a select. (INSERT and UPDATE statements are the
** same as a SELECT with only a single table in the FROM clause.) For
** example, if the SQL is this:
**
** SELECT * FROM t1, t2, t3 WHERE ...;
**
** Then the code generated is conceptually like the following:
**
** foreach row1 in t1 do \ Code generated
** foreach row2 in t2 do |-- by sqliteWhereBegin()
** foreach row3 in t3 do /
** ...
** end \ Code generated
** end |-- by sqliteWhereEnd()
** end /
**
** There are Btree cursors associated with each table. t1 uses cursor
** "base". t2 uses cursor "base+1". And so forth. This routine generates
** the code to open those cursors. sqliteWhereEnd() generates the code
** to close them.
**
** If the WHERE clause is empty, the foreach loops must each scan their
** entire tables. Thus a three-way join is an O(N^3) operation. But if
** the tables have indices and there are terms in the WHERE clause that
** refer to those indices, a complete table scan can be avoided and the
** code will run much faster. Most of the work of this routine is checking
** to see if there are indices that can be used to speed up the loop.
**
** Terms of the WHERE clause are also used to limit which rows actually
** make it to the "..." in the middle of the loop. After each "foreach",
** terms of the WHERE clause that use only terms in that loop and outer
** loops are evaluated and if false a jump is made around all subsequent
** inner loops (or around the "..." if the test occurs within the inner-
** most loop)
**
** OUTER JOINS
**
** An outer join of tables t1 and t2 is conceptally coded as follows:
**
** foreach row1 in t1 do
** flag = 0
** foreach row2 in t2 do
** start:
** ...
** flag = 1
** end
** if flag==0 goto start
** end
**
** In words, if the right
*/
WhereInfo *sqliteWhereBegin(
Parse *pParse, /* The parser context */
@@ -178,6 +230,11 @@ WhereInfo *sqliteWhereBegin(
int iDirectGt[32]; /* Term of the form ROWID>X or ROWID>=X */
ExprInfo aExpr[50]; /* The WHERE clause is divided into these expressions */
/* pushKey is only allowed if there is a single table (as in an INSERT or
** UPDATE statement)
*/
assert( pushKey==0 || pTabList->nSrc==1 );
/* Allocate space for aOrder[] and aiMem[]. */
aOrder = sqliteMalloc( sizeof(int) * pTabList->nSrc );
@@ -332,14 +389,17 @@ WhereInfo *sqliteWhereBegin(
** If score&2 is not 0 then there is an inequality used as the
** start key. (ex: "x>...");
**
** The IN operator as in "<expr> IN (...)" is treated the same as
** an equality comparison.
** The IN operator (as in "<expr> IN (...)") is treated the same as
** an equality comparison except that it can only be used on the
** left-most column of an index and other terms of the WHERE clause
** cannot be used in conjunction with the IN operator to help satisfy
** other columns of the index.
*/
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
int eqMask = 0; /* Index columns covered by an x=... constraint */
int ltMask = 0; /* Index columns covered by an x<... constraint */
int gtMask = 0; /* Index columns covered by an x>... constraint */
int inMask = 0; /* Index columns covered by an x IN .. constraint */
int eqMask = 0; /* Index columns covered by an x=... term */
int ltMask = 0; /* Index columns covered by an x<... term */
int gtMask = 0; /* Index columns covered by an x>... term */
int inMask = 0; /* Index columns covered by an x IN .. term */
int nEq, m, score;
if( pIdx->isDropped ) continue; /* Ignore dropped indices */
@@ -468,7 +528,7 @@ WhereInfo *sqliteWhereBegin(
/* If this is the right table of a LEFT OUTER JOIN, allocate and
** initialize a memory cell that record if this table matches any
** row of the left table in the join.
** row of the left table of the join.
*/
if( i>0 && (pTabList->a[i-1].jointype & JT_LEFT)!=0 ){
if( !pParse->nMem ) pParse->nMem++;
@@ -481,7 +541,9 @@ WhereInfo *sqliteWhereBegin(
pLevel->inOp = OP_Noop;
if( i<ARRAYSIZE(iDirectEq) && iDirectEq[i]>=0 ){
/* Case 1: We can directly reference a single row using an
** equality comparison against the ROWID field.
** equality comparison against the ROWID field. Or
** we reference multiple rows using a "rowid IN (...)"
** construct.
*/
k = iDirectEq[i];
assert( k<nExpr );
@@ -515,7 +577,8 @@ WhereInfo *sqliteWhereBegin(
sqliteVdbeAddOp(v, OP_NotExists, base+idx, brk);
pLevel->op = OP_Noop;
}else if( pIdx!=0 && pLevel->score%4==0 ){
/* Case 2: All index constraints are equality operators.
/* Case 2: There is an index and all terms of the WHERE clause that
** refer to the index use the "==" or "IN" operators.
*/
int start;
int testOp;
@@ -646,7 +709,7 @@ WhereInfo *sqliteWhereBegin(
}
haveKey = 0;
}else if( pIdx==0 ){
/* Case 4: There was no usable index. We must do a complete
/* Case 4: There is no usable index. We must do a complete
** scan of the entire database table.
*/
int start;
@@ -660,8 +723,12 @@ WhereInfo *sqliteWhereBegin(
pLevel->p2 = start;
haveKey = 0;
}else{
/* Case 5: The contraint on the right-most index field is
** an inequality.
/* Case 5: The WHERE clause term that refers to the right-most
** column of the index is an inequality. For example, if
** the index is on (x,y,z) and the WHERE clause is of the
** form "x=5 AND y<10" then this case is used. Only the
** right-most column can be an inequality - the rest must
** use the "==" operator.
*/
int score = pLevel->score;
int nEqColumn = score/4;
@@ -695,7 +762,7 @@ WhereInfo *sqliteWhereBegin(
}
}
/* Duplicate the equality contraint values because they will all be
/* Duplicate the equality term values because they will all be
** used twice: once to make the termination key and once to make the
** start key.
*/
@@ -705,7 +772,7 @@ WhereInfo *sqliteWhereBegin(
/* Generate the termination key. This is the key value that
** will end the search. There is no termination key if there
** are no equality contraints and no "X<..." constraint.
** are no equality terms and no "X<..." term.
*/
if( (score & 1)!=0 ){
for(k=0; k<nExpr; k++){
@@ -747,8 +814,8 @@ WhereInfo *sqliteWhereBegin(
}
/* Generate the start key. This is the key that defines the lower
** bound on the search. There is no start key if there are not
** equality constraints and if there is no "X>..." constraint. In
** bound on the search. There is no start key if there are no
** equality terms and if there is no "X>..." term. In
** that case, generate a "Rewind" instruction in place of the
** start key search.
*/
@@ -850,7 +917,8 @@ WhereInfo *sqliteWhereBegin(
}
/*
** Generate the end of the WHERE loop.
** Generate the end of the WHERE loop. See comments on
** sqliteWhereBegin() for additional information.
*/
void sqliteWhereEnd(WhereInfo *pWInfo){
Vdbe *v = pWInfo->pParse->pVdbe;