A native, non-blocking Postgres driver for Crystal
This driver now uses the crystal-db
project. Documention on connecting,
quering, etc, can be found at:
Add this to your shard.yml
and run crystal deps
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 9.1 through 9.4 and developed on 9.6 (travis does not currently have 9.5 support). Since it uses protocal 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 percision. In this
driver, it is represented as a PG::Numeric
which retians 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 abitrary percision, you can optionally
require pg_ext/big_rational
which adds #to_big_r
, but requires that you
have LibGMP installed.