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Overview
| Comment: | Use a hash table to improve the preformance of column name uniqueness checking. |
|---|---|
| Downloads: | Tarball | ZIP archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
5b08f29f458c600401860c7d70d8174c |
| User & Date: | drh 2015-11-14 20:52:43.849 |
Context
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2015-11-14
| ||
| 22:04 | Code simplification in sqlite3ColumnsFromExprList(). Update the %z format code so that it works with buffers obtained from sqlite3DbMalloc(). Add a testcase for the slow column name uniquifier. (check-in: 9272426057 user: drh tags: trunk) | |
| 20:52 | Use a hash table to improve the preformance of column name uniqueness checking. (check-in: 5b08f29f45 user: drh tags: trunk) | |
| 16:47 | Use randomness to prevent slowness in the generated-column-name uniqueness checking. (check-in: 6266712968 user: drh tags: trunk) | |
Changes
Changes to src/select.c.
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int i, j; /* Loop counters */
u32 cnt; /* Index added to make the name unique */
Column *aCol, *pCol; /* For looping over result columns */
int nCol; /* Number of columns in the result set */
Expr *p; /* Expression for a single result column */
char *zName; /* Column name */
int nName; /* Size of name in zName[] */
if( pEList ){
nCol = pEList->nExpr;
aCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
testcase( aCol==0 );
}else{
nCol = 0;
aCol = 0;
}
*pnCol = nCol;
*paCol = aCol;
| > > | | 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 |
int i, j; /* Loop counters */
u32 cnt; /* Index added to make the name unique */
Column *aCol, *pCol; /* For looping over result columns */
int nCol; /* Number of columns in the result set */
Expr *p; /* Expression for a single result column */
char *zName; /* Column name */
int nName; /* Size of name in zName[] */
Hash ht; /* Hash table of column names */
sqlite3HashInit(&ht);
if( pEList ){
nCol = pEList->nExpr;
aCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
testcase( aCol==0 );
}else{
nCol = 0;
aCol = 0;
}
*pnCol = nCol;
*paCol = aCol;
for(i=0, pCol=aCol; i<nCol && !db->mallocFailed; i++, pCol++){
/* Get an appropriate name for the column
*/
p = sqlite3ExprSkipCollate(pEList->a[i].pExpr);
if( (zName = pEList->a[i].zName)!=0 ){
/* If the column contains an "AS <name>" phrase, use <name> as the name */
zName = sqlite3DbStrDup(db, zName);
}else{
|
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assert( !ExprHasProperty(pColExpr, EP_IntValue) );
zName = sqlite3MPrintf(db, "%s", pColExpr->u.zToken);
}else{
/* Use the original text of the column expression as its name */
zName = sqlite3MPrintf(db, "%s", pEList->a[i].zSpan);
}
}
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assert( !ExprHasProperty(pColExpr, EP_IntValue) );
zName = sqlite3MPrintf(db, "%s", pColExpr->u.zToken);
}else{
/* Use the original text of the column expression as its name */
zName = sqlite3MPrintf(db, "%s", pEList->a[i].zSpan);
}
}
/* Make sure the column name is unique. If the name is not unique,
** append an integer to the name so that it becomes unique.
*/
cnt = 0;
while( zName && sqlite3HashFind(&ht, zName)!=0 ){
char *zNewName;
nName = sqlite3Strlen30(zName);
for(j=nName-1; j>0 && sqlite3Isdigit(zName[j]); j--){}
if( zName[j]==':' ) nName = j;
zName[nName] = 0;
zNewName = sqlite3MPrintf(db, "%s:%u", zName, ++cnt);
sqlite3DbFree(db, zName);
zName = zNewName;
if( cnt>3 ) sqlite3_randomness(sizeof(cnt), &cnt);
}
pCol->zName = zName;
if( zName && sqlite3HashInsert(&ht, zName, pCol)==pCol ){
db->mallocFailed = 1;
}
}
sqlite3HashClear(&ht);
if( db->mallocFailed ){
for(j=0; j<i; j++){
sqlite3DbFree(db, aCol[j].zName);
}
sqlite3DbFree(db, aCol);
*paCol = 0;
*pnCol = 0;
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