Output metrics about remove_orphan_files execution

[raunaqmorarka]

Description

alter table lineitem execute remove_orphan_files(retention_threshold => '0d');

            metric_name         | metric_value
    ----------------------------+--------------
     processed_manifests_count  |            2
     active_files_count         |           98
     scanned_files_count        |           97
     deleted_files_count        |            0

Additional context and related issues

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## Iceberg
* Produce metrics about execution in the output of remove_orphan_files procedure. ({issue}`26661`)

[Copilot]

Pull Request Overview

This PR enhances the Iceberg connector's remove_orphan_files procedure to output execution metrics. Instead of returning no information, the procedure now returns a table with metrics including manifest file processing count, valid files found, files scanned, and files deleted.

• Modified the executeTableExecute method signature across the SPI to return Map<String, Long> instead of void
• Enhanced the remove_orphan_files implementation to collect and return execution metrics
• Updated query result handling to display metrics as a two-column table with metric names and values

Reviewed Changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
core/trino-spi/src/main/java/io/trino/spi/connector/ConnectorMetadata.java	Changed executeTableExecute return type from void to Map<String, Long>
plugin/trino-iceberg/src/main/java/io/trino/plugin/iceberg/IcebergMetadata.java	Implemented metrics collection and return for remove_orphan_files procedure
core/trino-main/src/main/java/io/trino/operator/SimpleTableExecuteOperator.java	Updated operator to build result pages from returned metrics
core/trino-main/src/main/java/io/trino/sql/planner/plan/SimpleTableExecuteNode.java	Changed from single output symbol to list of symbols for metric name/value columns
docs/src/main/sphinx/connector/iceberg.md	Added documentation for the new metrics output format

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[Praveen2112]

Instead of skipping here, can we introduce something assertAlter or a dedicated method - which would set compareUpdate to false ?

[raunaqmorarka]

There should be no need for a special assertAlter method. We should be able to assert a more detailed output with assertUpdate itself.
This branch is written with the assumption that an update query can only produce a row count output and nothing else. Since ALTER commands did not output anything before, this branch was never executed before.
Now with the more detailed output, we need to skip over this branch to allow the assertion on detailed results.

[sopel39]

Maybe add boolean compareExecute boolean flag and special assertExecute method?

[sopel39]

lgtm % comments

[sopel39]

Maybe add boolean compareExecute boolean flag and special assertExecute method?