TL;DR: I was talking more about how the query is generated in Superet, not what
is valid SQL syntax. I believe that in this instance putting quotes around
`{col}` for Postgres is probably the simplest solution, but I would not apply
the same to all other engine types.
Long answer: I was referring to how Superset generates SQL queries. Currently
most other parts of the query are generated using SQL Alchemy constructs that
automatically detect the need for quotes. For example, selecting a column
`ColumnName` with an alias `col_alias` is in fact roughly defined as
`column('ColumnName').label('col_alias')`, which is then compiled into `SELECT
"ColumnName" AS col_alias`. If either require quoting, `ColumnName` in this
example, SQL Alchemy automatically puts quotes around it.
The problem here is that time grain expressions don't contain a reference to a
SQL Alchemy column object, but are static strings inside a `literal_column`
object, which makes it impossible for SQL Alchemy to apply conditional quoting.
See below where this happens:
https://github.com/apache/incubator-superset/blob/master/superset/connectors/sqla/models.py#L139-L143
I believe that Postgres is pickier than other engines in this case, i.e. most
other engines probably wouldn't require quotes around the column name in the
time grain expression. Therefore I would not force quotes into the time grain
expressions of other engines at this time.
[ Full content available at:
https://github.com/apache/incubator-superset/issues/5886 ]
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