A native, non-blocking Postgres driver for Crystal
This driver now uses the crystal-db
project. Documentation on connecting,
querying, etc, can be found at:
Add this to your shard.yml
and run shards install
dependencies:
pg:
github: will/crystal-pg
There are two ways to listen for notifications. For docs on NOTIFY
, please
read https://www.postgresql.org/docs/current/static/sql-notify.html.
- Any connection can be given a callback to run on notifications. However they are only received when other traffic is going on.
- A special listen-only connection can be established for instant notification
processing with
PG.connect_listen
.
# see full example in examples/listen_notify.cr
PG.connect_listen("postgres:///", "a", "b") do |n| # connect and listen on "a" and "b"
puts " got: #{n.payload} on #{n.channel}" # print notifications as they come in
end
Crystal-pg supports several popular array types. If you only need a 1 dimensional array, you can cast down to the appropriate Crystal type:
PG_DB.query_one("select ARRAY[1, null, 3]", &.read(Array(Int32?))
# => [1, nil, 3]
PG_DB.query_one("select '{hello, world}'::text[]", &.read(Array(String))
# => ["hello", "world"]
Crystal-pg is tested on Postgres versions 9.2 through 9.6. Since it uses protocol version 3, older versions probably also work but are not guaranteed.
- text
- boolean
- int8, int4, int2
- float4, float8
- timestamptz, date, timestamp (but no one should use ts when tstz exists!)
- json and jsonb
- uuid
- bytea
- numeric/decimal (1)
- varchar
- regtype
- geo types: point, box, path, lseg, polygon, circle, line
- array types: int8, int4, int2, float8, float4, bool, text
1: A note on numeric: In Postgres this type has arbitrary precision. In this
driver, it is represented as a PG::Numeric
which retains all precision, but
if you need to do any math on it, you will probably need to cast it to a
float first. If you need true arbitrary precision, you can optionally
require pg_ext/big_rational
which adds #to_big_r
, but requires that you
have LibGMP installed.