[SPARK-59348][SQL] Rewrite match-all LIKE '%' to IsNotNull in predicates

[david-mollitor-db]

What changes were proposed in this pull request?

col LIKE '%' (a pattern of only unescaped %) matches every non-null value, so a filter
WHERE col LIKE '%' keeps exactly the non-null rows. Today Spark evaluates it as a per-row
regex (.*) and pushes nothing to the data source.

This PR rewrites such patterns, in null-rejecting predicate positions, to IsNotNull(col):

Aggregate [count(1)]                    Aggregate [count(1)]
+- Filter (col LIKE '%')       ==>      +- Filter (isnotnull(col))
   +- Relation t                           +- Relation t

The rewrite is implemented in ReplaceNullWithFalseInPredicate, which already performs this
class of null-as-false simplification (cf. its existing Not(In(...))/Not(InSet(...))
handling). It fires only for a literal pattern of one or more % with the escape character not
being %; LIKE '', prefixes, and _ patterns are excluded. LikeAll/LikeAny are out of
scope.

Why are the changes needed?

• IsNotNull is far cheaper than compiling and running a regex per row.
• IsNotNull pushes down: Parquet/ORC skip row groups via null-count statistics; the raw LIKE
  regex does not.
• If col is non-nullable, IsNotNull(col) then folds to true and downstream
  PruneFilters/NullPropagation drop the filter entirely.

The pattern shows up in practice from dynamically-generated SQL (e.g. an empty search box
becoming LIKE '%').

Correctness. col LIKE '%' returns true for a non-null value and null for null,
whereas IsNotNull(col) returns false for null. They are equivalent only in null-rejecting
predicate positions, where null is treated as false. ReplaceNullWithFalseInPredicate
targets exactly those plan nodes (Filter, Join condition, MergeIntoTable,
DeleteFromTable, UpdateTable, ReplaceData, WriteDelta) and recurses only through
null-preserving operators (And, Or, If, CaseWhen), not into Not — so
NOT (col LIKE '%') and col LIKE '%' in a projection are left untouched, where null vs
false would be observable. No collation gate is needed: '%' matches every non-null value
under any collation.

Does this PR introduce any user-facing change?

No. Query results are identical; this is a performance improvement.

How was this patch tested?

New tests in ReplaceNullWithFalseInPredicateSuite:

• Rewritten: '%', '%%', '%%%' -> IsNotNull; through AND/OR; in a join condition.
• Not rewritten: prefix 'a%', empty '', % escaped (ESCAPE '%'), under NOT, and in a
  projection (the null-vs-false safety boundary).

build/sbt 'catalyst/testOnly *ReplaceNullWithFalseInPredicateSuite' passes (36/36); scalastyle
clean.

Was this patch authored or co-authored using generative AI tooling?

Generated-by: Claude Opus 4.8

[uros-b]

Nice rewrite, thank you @david-mollitor-db! Adding @stevomitric to also review this PR.