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40fb17791e
Commit the whole ./lib/ folder which stores the Crystal dependencies. This has a few benefits: - Allows to build the project without a connection to the Internet to retrieve dependencies. - Makes the project resistant against dependency re-tags which might include malicious code.
84 lines
2.6 KiB
Markdown
84 lines
2.6 KiB
Markdown
# crystal-pg
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A native, non-blocking Postgres driver for Crystal
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[](https://circleci.com/gh/will/crystal-pg/tree/master)
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## usage
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This driver now uses the `crystal-db` project. Documentation on connecting,
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querying, etc, can be found at:
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* https://crystal-lang.org/docs/database/
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* https://crystal-lang.org/docs/database/connection_pool.html
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### shards
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Add this to your `shard.yml` and run `shards install`
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``` yml
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dependencies:
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pg:
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github: will/crystal-pg
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```
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### Listen/Notify
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There are two ways to listen for notifications. For docs on `NOTIFY`, please
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read <https://www.postgresql.org/docs/current/static/sql-notify.html>.
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1. Any connection can be given a callback to run on notifications. However they
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are only received when other traffic is going on.
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2. A special listen-only connection can be established for instant notification
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processing with `PG.connect_listen`.
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``` crystal
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# see full example in examples/listen_notify.cr
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PG.connect_listen("postgres:///", "a", "b") do |n| # connect and listen on "a" and "b"
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puts " got: #{n.payload} on #{n.channel}" # print notifications as they come in
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end
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```
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### Arrays
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Crystal-pg supports several popular array types. If you only need a 1
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dimensional array, you can cast down to the appropriate Crystal type:
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``` crystal
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PG_DB.query_one("select ARRAY[1, null, 3]", &.read(Array(Int32?))
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# => [1, nil, 3]
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PG_DB.query_one("select '{hello, world}'::text[]", &.read(Array(String))
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# => ["hello", "world"]
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```
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## Requirements
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Crystal-pg is [regularly tested on](https://circleci.com/gh/will/crystal-pg)
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the Postgres versions the [Postgres project itself supports](https://www.postgresql.org/support/versioning/).
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Since it uses protocol version 3, older versions probably also work but are not guaranteed.
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## Supported Datatypes
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- text
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- boolean
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- int8, int4, int2
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- float4, float8
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- timestamptz, date, timestamp (but no one should use ts when tstz exists!)
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- json and jsonb
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- uuid
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- bytea
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- numeric/decimal (1)
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- varchar
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- regtype
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- geo types: point, box, path, lseg, polygon, circle, line
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- array types: int8, int4, int2, float8, float4, bool, text, numeric, timestamptz, date, timestamp
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1: A note on numeric: In Postgres this type has arbitrary precision. In this
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driver, it is represented as a `PG::Numeric` which retains all precision, but
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if you need to do any math on it, you will probably need to cast it to a
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float first. If you need true arbitrary precision, you can optionally
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require `pg_ext/big_rational` which adds `#to_big_r`, but requires that you
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have LibGMP installed.
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