Tricks
Download as PPT, PDF4 likes531 views
The document discusses various "hacks, internals, and sneaky tricks" for MongoDB including: 1. Nearly ordered keys have nice properties for indexing and querying data in order. 2. Using the embedded timestamp in Object IDs and sorting by ID to retrieve data in time order. 3. Storing UUIDs as binary data (BinData) for more efficient storage than strings. 4. Tips for using covered compound indexes to create materialized views of data without having to retrieve large fields.
![3. Store UUIDs as BinData rather than as strings > help misc b = new BinData(subtype,base64str) create a BSON BinData value b.subtype() the BinData subtype (0..255) b.length() length of the BinData data in bytes b.hex() the data as a hex encoded string b.base64() the data as a base 64 encoded string b.toString() byte type = BINDATA; char my_fieldname[]; unsigned len = 16; // 16 bytes byte subtype = 3; // UUID char data[16]; // http://bsonspec.org/#/specification](https://image.slidesharecdn.com/tricks-101118124105-phpapp01/85/Tricks-6-320.jpg)
![thanks questions? [email_address] @dmerr Please follow @mongodb on twitter. Sign up with 10gen for a 1 day “db design sanity check and design tuning” session. Email [email_address] 10gen is hiring in Bay Area and New York. Up Next 11:00-11:30 MongoDB and the Democratic Party -- A Case Study How Sunlight Labs Uses MongoDB](https://image.slidesharecdn.com/tricks-101118124105-phpapp01/85/Tricks-13-320.jpg)
Tricks
- 1. Crazy Stuff : Hacks, Internals, and Sneaky Tricks Dwight Merriman 10gen Mongo D.C. Conference
- 2. 1. nearly ordered keys have nice properties db.coll.ensureIndex( { x : 1 } ) db.coll.insert( { x : rand() } )
- 3. 1. nearly ordered keys db.coll.ensureIndex( { x : 1 } ) db.coll.insert( { x : rand() } )
- 4. 1. nearly ordered keys db.coll.ensureIndex( { x : 1 } ) db.coll.insert( { x : new Date() } )
- 5. 2. use the embedded time in Object IDs > obj = db.mycoll.findOne(); > obj._id.getTimestamp(); > db.mycoll.find().sort({_id:1}); // time order
- 6. 3. Store UUIDs as BinData rather than as strings > help misc b = new BinData(subtype,base64str) create a BSON BinData value b.subtype() the BinData subtype (0..255) b.length() length of the BinData data in bytes b.hex() the data as a hex encoded string b.base64() the data as a base 64 encoded string b.toString() byte type = BINDATA; char my_fieldname[]; unsigned len = 16; // 16 bytes byte subtype = 3; // UUID char data[16]; // http://bsonspec.org/#/specification
- 7. 4. Field name lengths
- 8. 4. Use covered compound indexes to create materialized views* * coming soon! -- your current build may not be fast yet > // { a : ..., b : ..., c : ..., d : ..., e : ..., f : reallybigdata, g : ... } > t.ensureIndex( { b : 1, d : 1, e : 1 } ) > f.find( {}, { b : 1, d : 1, e : 1 } )
- 9. 5. query the replication oplog
- 10. 6. making a replay log --diaglog or db._adminCommand( { diagLogging : 1 } ) Output is written to diaglog.bin_ 0 off. Also flushes any pending data to the file. 1 log writes 2 log reads 3 log both nc ''database_server_ip'' 27017 < ''somelog.bin'' | hexdump -c good for qa? good for bug reports?
- 11. 7. Manually padding records obj.padding = “aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa”; coll.insert(obj); coll.update({_id:obj._id}, { $unset : { padding : 1 } });
- 12. 8. other things you should be using (checklist) multikeys dot notation “ fire and forget” (i.e., don’t call getLastError for noncritical writes) upserts the HTTP admin page for replica sets
- 13. thanks questions? [email_address] @dmerr Please follow @mongodb on twitter. Sign up with 10gen for a 1 day “db design sanity check and design tuning” session. Email [email_address] 10gen is hiring in Bay Area and New York. Up Next 11:00-11:30 MongoDB and the Democratic Party -- A Case Study How Sunlight Labs Uses MongoDB