MQL

An OTP library to translate an SQL-like query into a MongoDB query. Based on idea by https://github.com/hachreak/mongoql

Example

E.g.

SELECT name, owner WHERE temperature>10 and (color="green" or color="red") ORDER BY name ASC LIMIT 2,3

will be translated into the following map, that can be used to query MongoDB:

#{batchsize => <<"3">>,
projector => [{<<"name">>,1},{<<"owner">>,1}],
query => {'$query',{{<<"temperature">>,{'$gt',10}},
		 {'$or',[{<<"color">>,{'$eq',<<"green"/utf8>>}},
				 {<<"color">>,{'$eq',<<"red">>}}]}},
		'$orderby',
		[{<<"name">>,1}]},
skip => <<"2">>}.

How to use

Collection = <<"list">>,
QueryString = "SELECT name, owner WHERE temperature>10 and (color=\"green\" or color=\"red\") ORDER BY name ASC LIMIT 2,3",
{ok, QMap} = mql:parse(QueryString),
Cursor=mongo:find(Collection, maps:get(query, QMap), maps:get(projector, QMap), maps:get(skip, QMap), maps:get(batchsize, QMap))
.

Placeholders

Also you can use placeholders. If placeholder value is atom, float or integer, it will be converted to string. If placeholder value is binary, it will be converted to string with leading and trailing double quotes. If placeholder value is list, it will remains unchanged.

Collection = <<"list">>,
QueryString = "SELECT name, owner WHERE temperature>:temp and (color=:color1 or color=:color2) ORDER BY name ASC LIMIT 2,3",
{ok, QMap} = mql:parse(QueryString, [{"temp", 25}, {"color1", "\"red\""}, {"color2", <<"green">>}]),
Cursor=mongo:find(Collection, maps:get(query, QMap), maps:get(projector, QMap), maps:get(skip, QMap), maps:get(batchsize, QMap))
.