Nadav Har'El cf5d7ce212 Alternator: drop unneeded "IS NOT NULL" clauses in MV of GSI/LSI ...

Scylla's materialized views naturally skip any base rows where the view's
key isn't set (is NULL), because we can't create a view row with a null
key. To make the user aware that this is happening, the user is required
to add "WHERE ... IS NOT NULL" for the view's key columns when defining
the view. However, the only place that these extra IS NOT NULL clauses
are checked are in the CQL "CREATE MATERIALIZED VIEWS" statement - they
are completely ignored in all other places in the code.

In particular, when we create a materialized view in Alternator (GSI or
LSI), we don't have to add these "IS NOT NULL" clauses, as they are
outright ignored. We didn't know they were ignored, and made an effort
to add them - but no matter how incorrectly we did it, it didn't matter :-)
In commit 2bf2ffd3ed it turned out we had a
typo that caused the wrong column name to be printed. Also, even today we
are still missing base key columns that aren't listed as a view key in
Alternator but still added as view clustering keys in Scylla - and again
the fact these were missing also didn't matter. So I think it's time to
stop pretending, and stop calculating these "IS NOT NULL" strings, so
this patch outright removes them from the Alternator view-creation code.

Beyond being a nice cleanup of unnecessary and inaccurate code, it
will also be necessary when we allow in later patches to index for
an Alternator attribute "x" not a real column x in the base table but
rather an element in the ":attrs" map - so adding a "x IS NOT NULL" isn't
only unnecessary, it is outright illegal: The expression evaluation code,
even though it doesn't do anything with the "IS NOT NULL" expression,
still verifies that "x" is a valid column, which it isn't.

Signed-off-by: Nadav Har'El <nyh@scylladb.com>

2024-09-09 12:09:25 +03:00

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