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https://issues.apache.org/jira/browse/FLINK-14533?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-14533:
-----------------------------------
Labels: pull-request-available (was: )
> PushFilterIntoTableSourceScanRule misses predicate pushdowns
> ------------------------------------------------------------
>
> Key: FLINK-14533
> URL: https://issues.apache.org/jira/browse/FLINK-14533
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Planner
> Affects Versions: 1.8.1, 1.8.2, 1.9.0, 1.9.1
> Reporter: Yuval Itzchakov
> Priority: Major
> Labels: pull-request-available
>
> When Flink attempts to perform predicate pushdown via
> `PushFilterIntoTableSourceScanRule`, it first checks the RexNodes to see if
> they can actually be pushed down to the source. It does that via
> `RexNodeToExpressionConverter.visitCall`, which traverses the nodes and
> eventually checks to see if it's a condition it knows:
> {code:scala}
> call.getOperator match {
> case SqlStdOperatorTable.OR => Option(operands.reduceLeft { (l, r) =>
> Or(l.asInstanceOf[PlannerExpression], r.asInstanceOf[PlannerExpression]) })
> case SqlStdOperatorTable.AND => Option(operands.reduceLeft { (l, r) =>
> And(l.asInstanceOf[PlannerExpression], r.asInstanceOf[PlannerExpression]) })
> case function: SqlFunction => lookupFunction(replace(function.getName),
> operands)
> case postfix: SqlPostfixOperator =>
> lookupFunction(replace(postfix.getName), operands)
> case operator@_ => lookupFunction(replace(s"${operator.getKind}"),
> operands)
> }
> {code}
> If we take as an example the following query:
> {code:sql}
> SELECT a, b, c
> FROM d
> WHERE LOWER(a) LIKE '%%foo%%' AND LOWER(b) LIKE '%%python%%'
> {code}
> When we hit the above pattern match, we fall to the case matching
> `SqlFunction`, as `LOWER` is of that type. Inside `lookupFunction`, we have a
> call to `functionCatalog.lookupFunction(name)` which looks up the given
> function in the function catalog. Eventually, we reach a static class called
> `BuiltInFunctionDefinitions`, which defines all of Flink's built in
> functions. When we iterate the list of built in functions as follows:
> {code:java}
> foundDefinition = BuiltInFunctionDefinitions.getDefinitions()
> .stream()
> .filter(f ->
> functionName.equals(normalizeName(f.getName())))
> .findFirst()
> .map(Function.identity());
> {code}
> This doesn't yield a result, because `LOWER`, inside
> `BuiltInFunctionDefinitions`, is defined as follows:
> {code:java}
> public static final BuiltInFunctionDefinition LOWER =
> new BuiltInFunctionDefinition.Builder()
> .name("lowerCase")
> .kind(SCALAR)
> .outputTypeStrategy(TypeStrategies.MISSING)
> .build();
> {code}
>
> And since we're using String to do the lookups, this fails to match, hence
> returning `null` and causing the entire pushdown to fail.
>
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