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Driver: Add page about Erlang (#420)
* Add dedicated page * Put each item on a separate page * Copy editing * Fix card on index page (merge conflict unresolved) * ODBC: Include ODBC installation instructions * epgsql: Generalize "SSL connection" section --------- Co-authored-by: Marios Trivyzas <5058131+matriv@users.noreply.github.com>
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‎docs/connect/erlang/epgsql.md‎

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(erlang-epgsql)=
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# Erlang epgsql
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:::{div} sd-text-muted
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Connect to CrateDB from Erlang using epgsql.
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:::
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:::{rubric} About
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:::
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[epgsql] is the designated Erlang PostgreSQL client library.
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:::{rubric} Synopsis
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:::
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`rebar.config`
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```erlang
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{deps,
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[
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{epgsql, ".*", {git, "https://github.com/epgsql/epgsql.git", {tag, "4.8.0"}}}
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]}.
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```
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`epgsql_example.erl`
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```erlang
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-module(epgsql_example).
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-export([start/0]).
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start() ->
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{ok, C} = epgsql:connect(#{
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host => "localhost",
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username => "crate",
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password => "crate",
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database => "doc",
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port => 5432,
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timeout => 4000
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}),
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{ok, _, Result} = epgsql:squery(C, "SELECT mountain, height FROM sys.summits ORDER BY height DESC LIMIT 3"),
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io:fwrite("~p~n", [Result]),
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ok = epgsql:close(C),
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init:stop().
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```
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:::{rubric} SSL connection
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:::
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Start the Erlang [SSL application] first,
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use the `ssl` and `ssl_opts` arguments on `epgsql:connect`, and
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replace username, password, and hostname with values matching
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your environment.
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Also use this variant to connect to CrateDB Cloud.
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```erlang
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start() ->
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ssl:start(),
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{ok, C} = epgsql:connect(#{
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host => "testcluster.cratedb.net",
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username => "admin",
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password => "password",
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database => "doc",
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port => 5432,
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ssl => true,
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ssl_opts => [{verify, verify_none}],
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timeout => 4000
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}),
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```
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:::{rubric} Example
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:::
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Create the files `rebar.config` and `epgsql_example.erl` including the synopsis code shared above.
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:::{include} ../_cratedb.md
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:::
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```shell
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rebar3 compile
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erlc epgsql_example.erl
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rebar3 shell --eval 'epgsql_example:start().'
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```
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[epgsql]: https://github.com/epgsql/epgsql
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[SSL application]: https://www.erlang.org/docs/28/apps/ssl/ssl_app.html

‎docs/connect/erlang/index.md‎

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(connect-erlang)=
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# Erlang
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:::{div} sd-text-muted
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Connect to CrateDB from Erlang applications.
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:::
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:::{toctree}
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odbc
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epgsql
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:::

‎docs/connect/erlang/odbc.md‎

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(erlang-odbc)=
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# Erlang ODBC
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:::{div} sd-text-muted
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Connect to CrateDB from Erlang using ODBC.
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:::
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:::{rubric} About
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:::
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Erlang includes an [ODBC application] out of the box that provides an
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interface to communicate with relational SQL-databases, see also
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[Erlang ODBC examples].
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:::{rubric} Install
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:::
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:::{include} ../odbc/install.md
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:::
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:::{rubric} Synopsis
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:::
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Before running the example, ensure the PostgreSQL ODBC driver is
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installed on your system.
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`odbc_example.erl`
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```erlang
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-module(odbc_example).
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main(_) ->
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odbc:start(),
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{ok, Ref} = odbc:connect("Driver={PostgreSQL Unicode};Server=localhost;Port=5432;Uid=crate;Pwd=crate", []),
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io:fwrite("~p~n", [odbc:sql_query(Ref, "SELECT mountain, height FROM sys.summits ORDER BY height DESC LIMIT 3")]),
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init:stop().
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```
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:::{rubric} CrateDB Cloud
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:::
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For connecting to CrateDB Cloud, start the Erlang [SSL application],
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add `sslmode=require`, and replace `Server`, `Uid`, and `Pwd` with
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values matching your environment.
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`odbc_example.erl`
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```erlang
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-module(odbc_example).
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main(_) ->
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ssl:start(),
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odbc:start(),
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{ok, Ref} = odbc:connect("Driver={PostgreSQL Unicode};Server=testcluster.cratedb.net;Port=5432;sslmode=require;Uid=admin;Pwd=password", []),
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io:fwrite("~p~n", [odbc:sql_query(Ref, "SELECT mountain, height FROM sys.summits ORDER BY height DESC LIMIT 3")]),
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init:stop().
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```
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:::{rubric} Example
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:::
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Create the file `odbc_example.erl` including the synopsis code shared above.
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:::{include} ../_cratedb.md
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:::
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```shell
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escript odbc_example.erl
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```
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[Erlang ODBC examples]: https://www.erlang.org/doc/apps/odbc/getting_started.html
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[ODBC application]: https://www.erlang.org/docs/28/apps/odbc/odbc.html
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[SSL application]: https://www.erlang.org/docs/28/apps/ssl/ssl_app.html

‎docs/connect/index.md‎

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Elixir
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::::
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::::{grid-item-card}
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:link: connect-erlang
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:link-type: ref
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:class-body: sd-fs-1 sd-text-center
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:class-footer: sd-fs-5 sd-font-weight-bold
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{fab}`erlang`
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+++
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Erlang
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::::
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::::{grid-item-card}
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:link: connect-go
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:link-type: ref
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:hidden:
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elixir/index
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erlang/index
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go/index
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java/index
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javascript

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