ESQL: COALESCE function #98542
ESQL: COALESCE function #98542
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This adds a `COALESCE` function that returns the first non-null value.
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Documentation preview: |
elasticsearchmachine
added
the
Team:QL (Deprecated)
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Pinging @elastic/es-ql (Team:QL) |
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Pinging @elastic/elasticsearch-esql (:Query Languages/ES|QL) |
| */ | ||
| @ParametersFactory | ||
| public static Iterable<Object[]> parameters() { | ||
| List<TestCaseSupplier> suppliers = new ArrayList<>(); |
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@not-napoleon you might be interested in this. I took a little time today to write a few functions and I ran into the need for this utility a few times actually.
| new FunctionDefinition[] { def(Case.class, Case::new, "case"), def(IsNull.class, IsNull::new, "is_null"), }, | ||
| new FunctionDefinition[] { def(Case.class, Case::new, "case") }, | ||
| // null | ||
| new FunctionDefinition[] { def(Coalesce.class, Coalesce::new, "coalesce"), def(IsNull.class, IsNull::new, "is_null"), }, |
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I've just removed the is_null / is_not_null functions. The same functionality is now available with IS NULL / IS NOT NULL.
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++. I'll get that merged.
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| for (int position = 0; position < children().size(); position++) { | ||
| if (dataType == null || dataType == NULL) { |
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For this check we have Expressions.isNull() that does a similar thing.
| } | ||
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| @Override | ||
| public boolean foldable() { |
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In ES SQL there is a Coalesce function which is interesting because it's also coming together with an Optimizer rule and the foldable method is much simpler (thanks to the aforementioned rule).
Otherwise, there is Expressions.foldable(children()); that can be used here.
The way I see it:
- either you merge this as is and create a GH issue to explore/improve NULL propagation for Coalesce (plus that optimizer rule)
- have a look at Coalesce in ES SQL and SQL's
Optimizer.PropagateNullableand have an adapted version in ESQL
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I'll open #98612 and replace with Expressions.foldable(children()) and we'll grab an optimizer rule later.
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| isNull | |||
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Even though Coalesce can have an arbitrary number of parameters, the tests here always use two.
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y=COALESCE(true, false, null) doesn't seem to work. The value for y is null. Only if I the last value is non-null it works.
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Huh. I thought I had tests for all that in the unit tests. I'll add more.
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Interesting! the break here was with an optimizer rule. I'll push a fix.
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In general is looking good, but I think more IT tests are needed for multi-argument variants, there is an optimization that can likely simplify the internals of Coalesce from QL point of view and the PR needs an update from main to incorporate the new changes regarding is null/is not null.
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Hi @nik9000, I've created a changelog YAML for you. |
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run elasticsearch-ci/docs |
This adds a `COALESCE` function that returns the first non-null value.
This adds a
COALESCEfunction that returns the first non-null value.