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Overview
| Comment: | Reduce the number of branches that need to be tested in the explainIndexRange() function of where.c. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | experimental |
| Files: | files | file ages | folders |
| SHA1: |
6fdae9a635a43e1bf7e4a480de141306 |
| User & Date: | drh 2010-11-12 15:36:00 |
Context
|
2010-11-12
| ||
| 17:41 | Add EXPLAIN QUERY PLAN test cases to check that the examples in the documentation work. (check-in: 85fdad85 user: dan tags: experimental) | |
| 15:36 | Reduce the number of branches that need to be tested in the explainIndexRange() function of where.c. (check-in: 6fdae9a6 user: drh tags: experimental) | |
|
2010-11-11
| ||
| 17:48 | Use "COMPOUND" instead of "COMPOSITE" in the EXPLAIN QUERY PLAN output to describe UNION, UNION ALL, EXCEPT and INTERSECT operations. (check-in: 28643b85 user: dan tags: experimental) | |
Changes
Changes to src/where.c.
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}
}
*pzAff = zAff;
return regBase;
}
#ifndef SQLITE_OMIT_EXPLAIN
/*
** Argument pLevel describes a strategy for scanning table pTab. This
** function returns a pointer to a string buffer containing a description
** of the subset of table rows scanned by the strategy in the form of an
** SQL expression. Or, if all rows are scanned, NULL is returned.
**
** For example, if the query:
................................................................................
** It is the responsibility of the caller to free the buffer when it is
** no longer required.
*/
static char *explainIndexRange(sqlite3 *db, WhereLevel *pLevel, Table *pTab){
WherePlan *pPlan = &pLevel->plan;
Index *pIndex = pPlan->u.pIdx;
int nEq = pPlan->nEq;
char *zRet = 0;
int i;
for(i=0; i<nEq; i++){
zRet = sqlite3MAppendf(db, zRet,
"%s%s%s=?", (zRet?zRet:""), (zRet?" AND ":""),
pTab->aCol[pIndex->aiColumn[i]].zName
);
}
if( pPlan->wsFlags&WHERE_BTM_LIMIT ){
zRet = sqlite3MAppendf(db, zRet,
"%s%s%s>?", (zRet?zRet:""), (zRet?" AND ":""),
pTab->aCol[pIndex->aiColumn[i]].zName
);
}
if( pPlan->wsFlags&WHERE_TOP_LIMIT ){
zRet = sqlite3MAppendf(db, zRet,
"%s%s%s<?", (zRet?zRet:""), (zRet?" AND ":""),
pTab->aCol[pIndex->aiColumn[i]].zName
);
}
if( zRet ){
zRet = sqlite3MAppendf(db, zRet, " (%s)", zRet);
}
return zRet;
}
/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
** record is added to the output to describe the table scan strategy in
** pLevel.
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}
}
*pzAff = zAff;
return regBase;
}
#ifndef SQLITE_OMIT_EXPLAIN
/*
** This routine is a helper for explainIndexRange() below
**
** pStr holds the text of an expression that we are building up one term
** at a time. This routine adds a new term to the end of the expression.
** Terms are separated by AND so add the "AND" text for second and subsequent
** terms only.
*/
static void explainAppendTerm(
StrAccum *pStr, /* The text expression being built */
int iTerm, /* Index of this term. First is zero */
const char *zColumn, /* Name of the column */
const char *zOp /* Name of the operator */
){
if( iTerm ) sqlite3StrAccumAppend(pStr, " AND ", 5);
sqlite3StrAccumAppend(pStr, zColumn, -1);
sqlite3StrAccumAppend(pStr, zOp, 1);
sqlite3StrAccumAppend(pStr, "?", 1);
}
/*
** Argument pLevel describes a strategy for scanning table pTab. This
** function returns a pointer to a string buffer containing a description
** of the subset of table rows scanned by the strategy in the form of an
** SQL expression. Or, if all rows are scanned, NULL is returned.
**
** For example, if the query:
................................................................................
** It is the responsibility of the caller to free the buffer when it is
** no longer required.
*/
static char *explainIndexRange(sqlite3 *db, WhereLevel *pLevel, Table *pTab){
WherePlan *pPlan = &pLevel->plan;
Index *pIndex = pPlan->u.pIdx;
int nEq = pPlan->nEq;
int i, j;
Column *aCol = pTab->aCol;
int *aiColumn = pIndex->aiColumn;
StrAccum txt;
if( nEq==0 && (pPlan->wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT))==0 ){
return 0;
}
sqlite3StrAccumInit(&txt, 0, 0, SQLITE_MAX_LENGTH);
sqlite3StrAccumAppend(&txt, " (", 2);
for(i=0; i<nEq; i++){
explainAppendTerm(&txt, i, aCol[aiColumn[i]].zName, "=");
}
j = i;
if( pPlan->wsFlags&WHERE_BTM_LIMIT ){
explainAppendTerm(&txt, i++, aCol[aiColumn[j]].zName, ">");
}
if( pPlan->wsFlags&WHERE_TOP_LIMIT ){
explainAppendTerm(&txt, i, aCol[aiColumn[j]].zName, "<");
}
sqlite3StrAccumAppend(&txt, ")", 1);
return sqlite3StrAccumFinish(&txt);
}
/*
** This function is a no-op unless currently processing an EXPLAIN QUERY PLAN
** command. If the query being compiled is an EXPLAIN QUERY PLAN, a single
** record is added to the output to describe the table scan strategy in
** pLevel.
|