clickhouse.cr

ClickHouse client for Crystal.

• crystal: 0.30.0

Usage

Clickhouse#execute returns a Clickhouse::Response which includes Enumerable(Array(Type)).

require "clickhouse"

client = Clickhouse.new(host: "localhost", port: 8123)

res = client.execute("SELECT 'foo', 2")
res.to_a                  # => [["foo", 2]]
res.rows                  # => 1
res.statistics.elapsed    # => 0.000671276
res.statistics.rows_read  # => 1
res.statistics.bytes_read # => 1
res.scalar                # => "foo"

Available DataType

• ClickHouse : src/clickhouse/data_type.cr

Schema

provides reflecting database objects.

• Database
• Table
• Column

client = Clickhouse.new
client.databases.map(&.name)
# => ["default", "system", ...

system = client.database("system")
system.tables.map(&.name)
# => ["aggregate_function_combinators", "asynchronous_metrics", ...

table = client.table("system", "parts")
table.columns.map(&.name)
# => ["partition", "name", ...

table.columns.select(&.type.date_time?).map(&.name)
# => ["modification_time", "remove_time", "min_time", "max_time"]

QueryTokenizer

This provides general purpose query tokenizer like well-known advanced search.

string = %( foo from:user1 "a:b" -bar -"-x:-y" )
tokens = Clickhouse::QueryTokenizer.tokenize(string)

puts tokens.map(&.inspect)
# [Included("foo"), Modified("user1"), Exactly("a:b"), -Included("bar"), -Exactly("-x:-y")]
puts tokens.map(&.to_s)
 # ["foo", "from:user1", "\"a:b\"", "-bar", "-\"-x:-y\""]

Installation

1. Add the dependency to your shard.yml:

dependencies:
  var:
    github: maiha/clickhouse.cr
    version: 0.3.0

2. Run shards install

Development

make test

Add a new DataType

1. src/clickhouse/data_type.cr Define ClickHouse DataType
2. src/clickhouse.cr Add corresponding Crystal class into Clickhouse::Type
3. src/clickhouse/cast.cr Add logic to combine them

Roadmap

• Core
  • [x] all primitive DataType
• Request
  • [ ] output format
• Response
  • [x] statistics methods
  • [ ] fetch value by field name

BREAKING CHANGES

• 0.3.0: Column#type is now String because enum can't handle Array(Int32) as its value.

Contributing

1. Fork it (https://github.com/maiha/clickhouse.cr/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• maiha - creator and maintainer