README.md in sequel-batches-0.1.3 vs README.md in sequel-batches-0.2.0
- old
+ new
@@ -1,13 +1,25 @@
# Sequel::Batches [](https://travis-ci.org/umbrellio/sequel-batches) [](https://coveralls.io/github/umbrellio/sequel-batches?branch=master)
This dataset extension provides the method #in_batches. The method splits dataset in parts and yields it.
-You can set following options:
- - pk Overrides primary key of your dataset
- - of sets chunk size (1000 by default)
- - start as a hash { [column]: <start_value> } represents frame start for batch processing
- - finish as a hash represents frame end
+Note: currently only PostgreSQL database is supported.
+
+You can set the following options:
+
+### pk
+Overrides primary key of your dataset. This option is required in case your table doesn't have a real PK, otherwise you will get `Sequel::Extensions::Batches::MissingPKError`.
+
+Note that you have to provide columns that don't contain NULL values, otherwise this may not work as intended. You will receive `Sequel::Extensions::Batches::NullPKError` in case batch processing detects a NULL value on it's way, but it's not guaranteed since it doesn't check all the rows for performance reasons.
+
+### of
+Sets chunk size (1000 by default).
+
+### start
+A hash `{ [column]: <start_value> }` that represents frame start for batch processing. Note that you will get `Sequel::Extensions::Batches::InvalidPKError` in case you provide a hash with wrong keys (ordering matters as well).
+
+### finish
+Same as `start` but represents the frame end.
## Installation
Add this line to your application's Gemfile: