remove DISTINCT ON statement

[stillmatic]

this function is used in the 'Enable Filter Select' function. Because it passes column_name to distinct the function is only usable by backends which support the DISTINCT ON statement, i.e. only postgres.

Here is (gist of) the error string I get:

SELECT DISTINCT ON is not supported [SQL: 'SELECT DISTINCT ON (column_name) column_name AS column_name \nFROM public.table_name \n LIMIT 10000 (Background on this error at: http://sqlalche.me/e/tw8g)

DISTINCT ON is only meaningful when selecting values from multiple columns. Because we are selecting rows from only one column, the above processed statement is logically identical to SELECT DISTINCT column_name FROM table_name LIMIT 10.

this passes CI / tox / etc since it's a one line change.

[xrmx]

You are changing the semantics though, and not sure the change in semantics won't introduce issues. What database are you using?

[codecov-io]

Codecov Report

Merging #4869 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4869   +/-   ##
=======================================
  Coverage   76.96%   76.96%           
=======================================
  Files          44       44           
  Lines        8534     8534           
=======================================
  Hits         6568     6568           
  Misses       1966     1966

Impacted Files	Coverage Δ
superset/connectors/sqla/models.py	74.23% <ø> (ø)	⬆️

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[mistercrunch]

LGTM