Fixes 1160: Prevent using cast column as part of __ctx_query

[manmorjim]

Prevent using cast column when it is date type as part of the alias __ctx_query for numeric histograms by keeping the original column.

Fixes #1160

[Algunenano]

Why not add a new column to the query with the casted date (__cdb_casted_date) and use that for the aggregation?

Also, we should add a test for this.

[manmorjim]

Why not add a new column to the query with the casted date (__cdb_casted_date) and use that for the aggregation?

:thinking: We have no control over the query of the ctx object in this class because it is given as parameter from an external call. However it could be addressed by modifying the line 139 with:

`
FROM
(
    SELECT * FROM (SELECT *, ${ctx.column} as __cdb_cast_date FROM (${ctx.query})) __ctx_query${extraTables} ${extraFilter}
)
`

And then in extraFilter:

extraFilter = `
  WHERE __ctx_query.__cdb_cast_date >= ${ctx.start}
    AND __ctx_query.__cdb_cast_date <= ${ctx.end}
`;

What do you think about this approach?

Also, we should add a test for this.

You're right. I'll mark this PR as draft until I add a test :+1:

[Algunenano]

thinking We have no control over the query of the ctx object in this class because it is given as parameter from an external call. However it could be addressed by modifying the line 139 with:

I'd modify https://github.com/CartoDB/Windshaft-cartodb/blob/fix_parsing_columns_histograms_1160/lib/models/dataview/histograms/numeric-histogram.js#L61 if we need it and set https://github.com/CartoDB/Windshaft-cartodb/blob/bb9d8f1385c817e925f35da43486a171c932c6c5/lib/models/dataview/histograms/numeric-histogram.js#L57 (column) to the new created column, that way there is no need to modify the query and we avoid the constant calls to the cast, right?

[manmorjim]

Thank you both! my first contribution to windshaft \o/ :tada: :rocket:

[dgaubert]

:shipit: