Group by Custom field: string measure support

[gokulanv]

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A simpler version of the query that I would like to write in Cube.Js is :
SELECT
con.id,
GROUP_CONCAT(t.title) FROM Contacts con LEFT JOIN Titles t on con.titleid = t.id;

Where I need to group only by con.id

Describe the solution you'd like
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SELECT
con.id,
GROUP_CONCAT(t.title) FROM Contacts con LEFT JOIN Titles t on con.titleid = t.id GROUP BY con.id;

Additional context
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The query generated by Cube Js is:
SELECT
con.id,
GROUP_CONCAT(t.title) FROM Contacts con LEFT JOIN Titles t on con.titleid = t.id GROUP BY 1, 2;
This gives an erroneous output

[paveltiunov]

@gokulanv Hey Gokulan! Right now it can be achieved by introducing string measure

cube(`Con`, {
  // ...,
  measures: {
    concat: {
      sql: `GROUP_CONCAT(${CUBE}.title)`,
      type: `number`
    }
  }
})

There's no dedicated string measure type as of right now. There's an issue for it: #260.