Advanced Shell Tips and Tricks

MongoDB Stockholm 2012 - Advanced Shell Tips and Tricks - Spencer Brody, Engineer, 10gen

Transcript

1. MASTERING THE SHELL Spencer Brody – spencer@10gen.com @stbrody
2. What is the shell? •  vars •  functions •  data structs + types Embedded Javascript Interpreter •  ObjectId("...") •  new Date() •  Object.bsonsize() Global Functions and Objects •  db["collection"].find/count/update •  short-hand for collections MongoDB driver Exposed •  Doesn't require quoted keys •  Don’t copy and paste too much JSON-like stuff
3. What is it good for? ¨  Interactive development/prototyping ¨  Debugging ¨  Test scripting (ex. MongoDB’s own regression tests) ¨  Administrative operations, lightweight scripting ¨  Learning (and teaching) MongoDB ¨  Not building apps, probably
4. Interactive mode ¨  Demo now J ¨  for(i = 0; i <1000; i++) { db.test.insert({x:i, ts: new Date()}) }
5. Command Line ¨  --eval ¤  Printing values ¨  Pass in a script
6. Loading Scripts ¨  Command line ¨  load() – also runs
7. The Bad: JS Types ¨  Numbers Suck (but getting better) ¤  32/64bit signed (int/long) – 1.5.4>NumberLong(“”) ¤  Displayed funny ¤  Everything is a 64bit fp (double) ¨  Dates are a challenge ¤  new Date(“1/1/1”) ¤  Not Date(“1/1/1”) -> string
8. The Bad: JS is Slow ¨  Shell ¤  Safe/GLE ¤  Loops and updates ¤  Data conversions ¨  Server ¤  It pretty much applies here too ¤  Be careful with numbers as well
9. Shell helpers ¨  Show collections/dbs ¨  Use <db>
10. Cursors ¨  Cursors printed by iterating and printing 20 values ¨  find automatically sets “it” global var ¨  Cursors as first-class objects
11. Run Commands ¨  db.runCommand({…}) ¨  db.runCommand(“getLastError”) ¨  db.adminCommand({…})
12. Useful Commands ¨  getCmdLineOpts ¨  ping ¨  isMaster ¨  reIndex ¨  sharding ¨  replication
13. Help > help > help admin > help misc > db.help() > db.coll.help()
14. Expose Functions ¨  Leave off the () to see the function: > db.getSiblingDB function (name) { return this.getMongo().getDB(name);
15. 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)
16. Print all Indexes db.getCollectionNames(). forEach(function(x){ print(“Collection: “ + x); printjson(db[x].getIndexes()); })
17. 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; } });
18. .mongorc.js ¨  File loaded at startup ¨  Can be used to setup functions you always want defined ¨  Can set custom prompts
19. Questions ¨  That’s all…folks! ¨  try.mongodb.org – web based shell ¨  spencer@10gen.com