integrate concat_ws for memsql and snowflake #2603
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What type of PR is this?
What does this PR do / why is it needed ?
The current translation of joinStrings from PURE is to the CONCAT method in SQL. In some of the SQL implementations, including MemSQL and Snowflake that are addressed in this MR, the CONCAT method concatenates the variables without a delimiter, and produces null when one the values is null.
Example1: ['A', 'B']->joinStrings('|') in PURE, produces SQL CONCAT('A', 'B', '|') which evaluates to 'AB|'.
Example2: ['A', null]->joinStrings('|') in PURE, produces SQL CONCAT('A', null, '|') which evaluates to NULL.
Fix:
This MR maps the joinStrings for MemSQL and Snowflake to CONCAT_WS instead.
CONCAT_WS concatenates the variables using a delimiter
Example1: ['A', 'B']->joinStrings('|') in PURE, produces SQL CONCAT_WS('|', 'A', 'B') which evaluates to 'A|B'.
Example2: ['A', 'B']->joinStrings('|') in PURE, produces SQL CONCAT_WS('|', 'A', NULL) which evaluates to 'A'.
Which issue(s) this PR fixes:
Fixes #
Other notes for reviewers:
Does this PR introduce a user-facing change?