Build a match candidate from an index defined on an unnested record type

[g31pranjal]

Makes an index defined on an UnnestedRecordType usable by the Cascades planner, and covers it end to end.

Three preconditions were missing, each one gating the next:

• MetaDataPlanContext never collected the indexes of a synthetic record type, so such an index was not in the list a candidate could be expanded from.
• IndexExpansionInfo described the base with the name-taking getPlannerType, which resolves stored record types only.
• ValueIndexExpansionVisitor always built the base as a scan of the stored types plus a type filter, so SyntheticRecordType.expand was never called.

With those in place, matching and compensating against such a candidate works, and a covering scan can read the __positions tuple, which a ListKeyExpression places one level deeper in the index entry's key.

unnested-record-type-indexes.yamsql asserts the covering plan and the rows for seven queries over one such index: the query the index was defined for, the same unnesting without the ordering, a prefix of the key, the PartiQL spelling of the unnesting, and equalities binding one or both leading key columns.

Why this is marked do-not-merge

The branch carries the relational-side work of #4467 as a merge, because that is what generates the synthetic table from an index definition. #4467 lives on a fork, so this PR cannot be based on it. It is based on #4619 instead, and the diff therefore shows #4467's changes as well. Once #4467 merges, this branch will be rebased and the diff will narrow to its own commits.

The second commit refreshes plan expectations in array-join-at.yamsql and in-predicate.yamsql. Those mismatches are present on this branch without the candidate change, and belong to the branches those files came from; the commit is kept separate so it can be dropped on that rebase.

[github-actions]

📊 Metrics Diff Analysis Report

Summary

• New queries: 7
• Dropped queries: 0
• Plan changed + metrics changed: 7
• Plan unchanged + metrics changed: 2

ℹ️ About this analysis

This automated analysis compares query planner metrics between the base branch and this PR. It categorizes changes into:

• New queries: Queries added in this PR
• Dropped queries: Queries removed in this PR. These should be reviewed to ensure we are not losing coverage.
• Plan changed + metrics changed: The query plan has changed along with planner metrics.
• Metrics only changed: Same plan but different metrics

The last category in particular may indicate planner regressions that should be investigated.

New Queries

Count of new queries by file:

• yaml-tests/src/test/resources/unnested-record-type-indexes.metrics.yaml: 7

Plan and Metrics Changed

These queries experienced both plan and metrics changes. This generally indicates that there was some planner change
that means the planning for this query may be substantially different. Some amount of query plan metrics change is expected,
but the reviewer should still validate that these changes are not excessive.

Total: 7 queries

Statistical Summary (Plan and Metrics Changed)

task_count:

• Average change: -7.4
• Median change: -11
• Standard deviation: 4.2
• Range: -11 to -2
• Queries changed: 7
• No regressions! 🎉

task_count % change distribution (7 queries, bin = 2%):

     Range                                  n
----------  ------------------------------  ---
[-2%, +0%)  ██████████████████████████████  7

transform_count:

• Average change: -1.0
• Median change: -1
• Standard deviation: 0.0
• Range: -1 to -1
• Queries changed: 4
• No regressions! 🎉

transform_count % change distribution (4 queries, bin = 2%):

     Range                                  n
----------  ------------------------------  ---
[-2%, +0%)  ██████████████████████████████  4

transform_yield_count:

• Average change: -1.0
• Median change: -1
• Standard deviation: 0.0
• Range: -1 to -1
• Queries changed: 4
• No regressions! 🎉

transform_yield_count % change distribution (4 queries, bin = 2%):

     Range                                  n
----------  ------------------------------  ---
[-2%, +0%)  ██████████████████████████████  4

insert_new_count:

• Average change: -1.0
• Median change: -1
• Standard deviation: 0.0
• Range: -1 to -1
• Queries changed: 4
• No regressions! 🎉

insert_new_count % change distribution (4 queries, bin = 2%):

     Range                                  n
----------  ------------------------------  ---
[-2%, +0%)  ██████████████████████████████  4

There were no queries with significant regressions detected.

Minor Changes (Plan and Metrics Changed)

In addition, there were 7 queries with minor changes.

Only Metrics Changed

These queries experienced only metrics changes without any plan changes. If these metrics have substantially changed,
then a planner change has been made which affects planner performance but does not correlate with any new outcomes,
which could indicate a regression.

Total: 2 queries

Statistical Summary (Only Metrics Changed)

task_count:

• Average change: -175.0
• Median change: -175
• Standard deviation: 0.0
• Range: -175 to -175
• Queries changed: 1
• No regressions! 🎉

transform_count:

• Average change: -57.0
• Median change: -57
• Standard deviation: 0.0
• Range: -57 to -57
• Queries changed: 1
• No regressions! 🎉

transform_yield_count:

• Average change: -9.0
• Median change: -9
• Standard deviation: 0.0
• Range: -9 to -9
• Queries changed: 1
• No regressions! 🎉

insert_new_count:

• Average change: -10.0
• Average regression: +1.0
• Median change: +1
• Median regression: +1
• Standard deviation: 11.0
• Standard deviation of regressions: 0.0
• Range: -21 to +1
• Range of regressions: +1 to +1
• Queries changed: 2
• Queries regressed: 1

Significant Regressions (Only Metrics Changed)

There were 2 outliers detected. Outlier queries have a significant regression in at least one field. Statistically, this represents either an increase of more than two standard deviations above the mean or a large absolute increase (e.g., 100).

• yaml-tests/src/test/resources/subquery-tests.metrics.yaml:88: EXPLAIN select sq.idr, sq.z from (select * from r where idr = 1) sq, (select f from sq.nr where f > 10) sq2 where sq.z = 10 AND sq2.f is not null
  • explain: ISCAN(IR [EQUALS promote(@c17 AS INT), EQUALS promote(@c31 AS INT)]) | FLATMAP q0 -> { EXPLODE q0.NR | FILTER _.F GREATER_THAN promote(@c31 AS INT) AND _.F NOT_NULL AS q1 RETURN (q0.IDR AS IDR, q0.Z AS Z) }
  • insert_new_count: 82 -> 83 (+1)
• yaml-tests/src/test/resources/valid-identifiers.metrics.yaml:29: EXPLAIN select t.id from "foo.table$nested.repeated" as t where exists (select * from t."level0.field1" as b, b."level1$field.1" where "level2$array.field.1" = 10)
  • explain: COVERING(foo.table$nested.repeated.idx.field.1.1.1 [EQUALS promote(@c26 AS LONG)] -> [ID: KEY:[2]]) | MAP (_.ID AS ID)
  • task_count: 899 -> 724 (-175)
  • transform_count: 320 -> 263 (-57)
  • transform_yield_count: 69 -> 60 (-9)
  • insert_new_count: 94 -> 73 (-21)