Gagan Saksena

Some recipes/notes from using CouchDB. These could be valuable someday for others navigating their way in these waters. For now mostly a placeholder for things I'm learning. This is work in progress!

Handy shortcuts

There are a number of handy shortcuts for doing standard reduce tasks- Checkout Built-In_Reduce_Functions for more details.

SQL Recipes in Map/Reduce

A collection of handy recipes to do common tasks in map/reduce. This page is still in development- checkout this book's page for some useful details- Views for SQL jockeys

For the purpose of these recipes- the equivalent SQL table looks like this-

CREATE TABLE Foo ( 
  Name CHAR(256),
  Age INTEGER,
  StartDate DATE
);

SQL

Map

Reduce

Notes

SELECT COUNT(*) FROM Foo;

function (doc) { emit(doc._id, 1); }

_count

SELECT COUNT(*) FROM Foo WHERE Foo.Age ="21";

function (doc) { emit(doc.age, null); }

_count

Fetch view with ?key=21

SELECT DISTINCT Age FROM Foo;

function (doc) { emit(doc.age, true); }

function (key, value, rereduce) { // todo }

GROUP BY example

function (doc) { // todo }

GROUP BY with SORT BY example

function (doc) { // todo }


CategoryHomepage