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https://issues.apache.org/jira/browse/COUCHDB-220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12695852#action_12695852
]
Robert Newson commented on COUCHDB-220:
---------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
couchTests.attachment_sparseness= function(debug) {
var db = new CouchDB("test_suite_db");
db.deleteDb();
db.createDb();
if (debug) debugger;
for (i = 0; i < 1000; i++) {
var binAttDoc = {
_id: (i).toString(),
_attachments:{
"foo.txt": {
content_type:"text/plain",
data: "VGhpcyBpcyBhIGJhc2U2NCBlbmNvZGVkIHRleHQ="
}
}
}
var save_response = db.save(binAttDoc);
T(save_response.ok);
}
var before = db.info().disk_size;
// Compact it.
T(db.compact().ok);
T(db.last_req.status == 202);
// compaction isn't instantaneous, loop until done
while (db.info().compact_running) {};
var after = db.info().disk_size;
// Compaction should reduce the database slightly, but not
// orders of magnitude (unless attachments introduce sparseness)
T(after > before * 0.1, "database shrunk massively after compaction.");
};
> Extreme sparseness in couch files
> ---------------------------------
>
> Key: COUCHDB-220
> URL: https://issues.apache.org/jira/browse/COUCHDB-220
> Project: CouchDB
> Issue Type: Bug
> Components: Database Core
> Affects Versions: 0.9
> Environment: ubuntu 8.10 64-bit, ext3
> Reporter: Robert Newson
>
> When adding ten thousand documents, each with a small attachment, the
> discrepancy between reported file size and actual file size becomes huge;
> ls -lh shard0.couch
> 698M 2009-01-23 13:42 shard0.couch
> du -sh shard0.couch
> 57M shard0.couch
> On filesystems that do not support write holes, this will cause an order of
> magnitude more I/O.
> I think it was introduced by the streaming attachment patch as each
> attachment is followed by huge swathes of zeroes when viewed with 'hd -v'.
> Compacting this database reduced it to 7.8mb, indicating other sparseness
> besides attachments.
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