diff --git a/README.md b/README.md index 2f42ec1..8a634ea 100644 --- a/README.md +++ b/README.md @@ -12,7 +12,7 @@ Version: 0.0.1 **decoderbufs** is released under the MIT license (See LICENSE file). **Shoutouts:** -- [The PostgreSQL Team](https://postgresql.org) for adding logical decoding support. This is a immensely useful feature. +- [The PostgreSQL Team](https://postgresql.org) for adding [logical decoding](http://www.postgresql.org/docs/9.4/static/logicaldecoding.html) support. This is a immensely useful feature. - [Michael Paquier](https://github.com/michaelpq) for his [decoder_raw](https://github.com/michaelpq/pg_plugins/tree/master/decoder_raw) project and blog posts as a guide to teach myself how to write a PostgreSQL logical decoder output plugin. - [Martin Kleppmann](https://github.com/ept) for making me aware that PostgreSQL was working on logical decoding. @@ -67,16 +67,20 @@ And restart PostgreSQL. ### Usage -- can use SQL for demo purposes select * from pg_create_logical_replication_slot('decoderbufs_demo', 'decoderbufs'); - -- DO SOME TABLE MODIFICATIONS + + -- DO SOME TABLE MODIFICATIONS (see below about UPDATE/DELETE) + -- peek at WAL changes using decoderbufs debug mode for SQL console select data from pg_logical_slot_peek_changes('decoderbufs_demo', NULL, NULL, 'debug-mode', '1'); -- get WAL changes using decoderbufs to update the WAL position select data from pg_logical_slot_get_changes('decoderbufs_demo', NULL, NULL, 'debug-mode', '1'); + -- check the WAL position of logical replicators select * from pg_replication_slots where slot_type = 'logical'; -The binary format uses simple frame encoding, which uses an 8-byte length (uint64_t) followed by that number of bytes for the Protocol Buffer payload. The -easy way to test check this out is to use _pg\_recvlogical_ like so: +If you're performing an UPDATE/DELETE on your table and you don't see results for those operations from logical decoding, make sure you have set [REPLICA IDENTITY](http://www.postgresql.org/docs/9.4/static/sql-altertable.html#SQL-CREATETABLE-REPLICA-IDENTITY) appropriately for your use case. + +The binary format uses simple frame encoding, which uses an 8-byte length (uint64\_t) followed by that number of bytes for the Protocol Buffer payload. The easy way to test check this out is to use _pg\_recvlogical_ like so: pg_recvlogical -h localhost -d -U -w -S decoderbufs_demo -P decoderbufs -f decoderbuf.frames -s 1 -F 1 --start