Mastering the MongoDB JavaScript Shell

1. Hacking the Shell Raw MongoDB (as you like it) Scott Hernandez – scott@10gen

2. What is the shell?

3. What is it good for? Debugging Queries/Syntax Testing Administration Scripting Glue Not for building apps, probably

4. The Bad: JS Types Numbers Suck (but getting better) 32/64bit signed (int/long) – 1.5.4>NumberLong(“”) Displayed funny in early versions Everything is a 64bit fp (double) Dates are a challenge new Date(“1/1/1”) new ISODate(…) Not Date(“1/1/1”) -> string

5. The Bad: JS is Slow Shell Always Safe/GLE Loops and updates Data conversions Server It pretty much applies here too Be careful with numbers as well

6. Insert, Save, Update, Remove Demo now  for(i = 0; i <1000; i++) { db.test.insert({x:i, ts: new Date()}) }

7. Command Line --eval it/cursor Printing values Pass in a script

8. Loading Scripts Command line load() – also runs

9. Run Commands db.runCommand({…}) db.runCommand(“getLastError”)

10. Useful Commands getCmdLineOpts ping isMaster reIndex sharding replication

11. Profiling setProfilingLevel(lvl, <ms>) 0: none 1: time-based 2: all getProfilingLevel() Reading from profile collection >db.system.profile.find()

12. Help > help > help admin > help misc > db.help() > db.coll.help()

13. Expose Functions Leave off the () to see the function: > db.getSisterDB function (name) { return this.getMongo().getDB(name);

14. Cool functions printjson -> tojson forEach on array/query/cursor > [{x:1},{y:1}].forEach(function(x){printjson(x)}) { "x" : 1 } { "y" : 1 } Object.bsonsize Object.bsonsize(c.findOne({name:”scott”})) load(file) run(file)

15. Print all Indexes db.getCollectionNames(). forEach(function(x){ print(“Collection: “ + x); printjson(db[x].getIndexes()); })

16. Getting the Biggest Doc var cursor = db.coll.find(); var biggest=0; var doc = {}; cursor.forEach(function (x) { var size = Object.bsonsize(x); if (size > biggest) { biggest=size; doc = x; } });

17. Cursors: it “it” global var find automatically sets it

18. Aliases Show collections/tables

19. DBRef Has fetch() Easy to create

20. Questions That’s all…folks! scott@10gen.com