gianm opened a new pull request, #15609:
URL: https://github.com/apache/druid/pull/15609
COALESCE is converted by Calcite's parser to CASE, which is largely
counterproductive for us, because it ends up duplicating expressions. In the
current code we end up un-doing it in our CaseOperatorConversion. This patch
has a different approach:
1) Add CaseToCoalesceRule to convert CASE back to COALESCE earlier, before
the Volcano planner runs, using CaseToCoalesceRule.
2) Add FilterDecomposeCoalesceRule to decompose calls like
"f(COALESCE(x, y))" into "(x IS NOT NULL AND f(x)) OR (x IS NULL AND
f(y))".
This helps use indexes when available on x and y.
3) Add CoalesceLookupRule to push COALESCE into the third arg of LOOKUP.
4) Add a native "coalesce" function so we can convert 3+ arg COALESCE.
The advantage of this approach is that by un-doing the CASE to COALESCE
conversion earlier, we have flexibility to do more stuff with COALESCE (like
decomposition and pushing into LOOKUP).
SEARCH is an operator used internally by Calcite to represent matching an
argument against some set of ranges. This patch improves our handling of SEARCH
in two ways:
1) Expand NOT points (point "holes" in the range set) from SEARCH as
`!(a || b)` rather than `!a && !b`, which makes it possible to convert
them to a "not" of "in" filter later.
2) Generate those nice conversions for NOT points even if the SEARCH
is not composed of 100% NOT points. Without this change, a SEARCH
for "x NOT IN ('a', 'b') AND x < 'm'" would get converted like
"x < 'a' OR (x > 'a' AND x < 'b') OR (x > 'b' AND x < 'm')".
One of the steps we take when generating Druid queries from Calcite plans is
to optimize native filters. This patch improves this step:
1) Extract common ANDed predicates in ConvertSelectorsToIns, so we can
convert "(a && x = 'b') || (a && x = 'c')" into "a && x IN ('b', 'c')".
2) Speed up CombineAndSimplifyBounds and ConvertSelectorsToIns on
ORs with lots of children by adjusting the logic to avoid calling
"indexOf" and "remove" on an ArrayList.
3) Refactor ConvertSelectorsToIns to reduce duplicated code between the
handling for "selector" and "equals" filters.
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