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| author | unknown <konstantin@mysql.com> | 2004-06-10 01:30:39 +0400 |
|---|---|---|
| committer | unknown <konstantin@mysql.com> | 2004-06-10 01:30:39 +0400 |
| commit | f468b91f3796848d46c2b5d7919f8c762593a784 (patch) | |
| tree | 4e84fc20ffbbb0ada96ebc037f4d9d50ad94a09b /myisam | |
| parent | 350ad5003e90c4129a69937afaf7d87b828a506c (diff) | |
| download | mariadb-git-f468b91f3796848d46c2b5d7919f8c762593a784.tar.gz | |
Fix for Bug#3904 "COUNT DISTINCT performance anomaly in 4.1"
The bug was caused by error in hash calculation function: it
always returned hash value for last field in a composite key, so
for keys like (a text, b char(1)) we were always
getting bad hash values.
myisam/mi_unique.c:
Fix for bug #3904:
We should take into account existing hash value when calculating hash for
next key in a composite unique index.
Diffstat (limited to 'myisam')
| -rw-r--r-- | myisam/mi_unique.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/myisam/mi_unique.c b/myisam/mi_unique.c index 38b4ed93311..4d82858c9ad 100644 --- a/myisam/mi_unique.c +++ b/myisam/mi_unique.c @@ -71,6 +71,7 @@ ha_checksum mi_unique_hash(MI_UNIQUEDEF *def, const byte *record) const byte *pos, *end; ha_checksum crc=0; HA_KEYSEG *keyseg; + ulong seed= 4; for (keyseg=def->seg ; keyseg < def->end ; keyseg++) { @@ -108,9 +109,8 @@ ha_checksum mi_unique_hash(MI_UNIQUEDEF *def, const byte *record) end= pos+length; if (type == HA_KEYTYPE_TEXT || type == HA_KEYTYPE_VARTEXT) { - ulong nr=1, nr2=4; - keyseg->charset->coll->hash_sort(keyseg->charset,(const uchar*)pos,length,&nr, &nr2); - crc=nr; + keyseg->charset->coll->hash_sort(keyseg->charset, + (const uchar*) pos, length, &crc, &seed); } else while (pos != end) |