crystal-pg

A native, non-blocking Postgres driver for Crystal

usage

This driver now uses the crystal-db project. Documentation on connecting, querying, etc, can be found at:

• https://crystal-lang.org/docs/database/
• https://crystal-lang.org/docs/database/connection_pool.html

shards

Add this to your shard.yml and run shards install

dependencies:
  pg:
    github: will/crystal-pg

Listen/Notify

There are two ways to listen for notifications. For docs on NOTIFY, please read https://www.postgresql.org/docs/current/static/sql-notify.html.

1. Any connection can be given a callback to run on notifications. However they are only received when other traffic is going on.
2. 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

Arrays

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"]

Requirements

Crystal-pg is regularly tested on Postgres versions 9.2 through 9.6 and has been confirmed to support all newer releases (up to version 11). Since it uses protocol version 3, older versions probably also work but are not guaranteed.

Supported Datatypes

• 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.