[lake/paimon] Support custom Paimon path

[wzx140]

Summary

• Allow users to set the Paimon path option through custom table properties.
• Reject altering paimon.path after datalake has been enabled for the table.
• Add regression coverage for unsettable Paimon options and paimon.path alter validation.

Test Plan

• JAVA_HOME=/opt/homebrew/Cellar/openjdk@11/11.0.24/libexec/openjdk.jdk/Contents/Home ./mvnw -pl fluss-lake/fluss-lake-paimon -am -Dtest=LakeEnabledTableCreateITCase#testCreateLakeEnableTableWithUnsettablePaimonOptions+testAlterPaimonPathOnlyWhenLakeDisabled -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false test

[Copilot]

Pull request overview

Enables configuring a custom Paimon table path via table custom properties, and adds server-side validation to prevent changing paimon.path once a table is datalake-enabled (plus regression coverage for the new behavior).

Changes:

• Allow paimon.path to be set by removing CoreOptions.PATH from Paimon’s “unsettable options” list.
• Extend alter-table property validation to consider custom property keys and reject paimon.path changes when datalake is enabled.
• Add IT coverage for unsettable Paimon options and paimon.path alter validation.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
fluss-server/src/main/java/org/apache/fluss/server/utils/TableDescriptorValidation.java	Adds validation for altering paimon.path via custom properties when datalake is enabled.
fluss-server/src/main/java/org/apache/fluss/server/coordinator/MetadataManager.java	Passes custom-keys-to-change into alter validation during table property updates.
fluss-lake/fluss-lake-paimon/src/main/java/org/apache/fluss/lake/paimon/utils/PaimonConversions.java	Makes Paimon path user-settable by removing it from the unsettable-options list.
fluss-lake/fluss-lake-paimon/src/test/java/org/apache/fluss/lake/paimon/LakeEnabledTableCreateITCase.java	Adds regression tests for unsettable options and paimon.path alter restrictions.

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[luoyuxia]

@wzx140 Thanks for the pr.
IIUC, paimon.path is intended to customize the physical location only when the Paimon table is created. Allowing it to be changed after the table has already been created looks unsafe to me, because changing this option does not migrate the existing Paimon metadata/data from the old path to the new one.

The current check only rejects changing paimon.path while table.datalake.enabled is true. However, a table can be enabled once, then disabled later, while the Paimon table still exists.
In that state, altering paimon.path would still be allowed. Could we make paimon.path a create-time-only option, or reject changing it once the lake table has ever been created?

[wzx140]

@wzx140 Thanks for the pr. IIUC, paimon.path is intended to customize the physical location only when the Paimon table is created. Allowing it to be changed after the table has already been created looks unsafe to me, because changing this option does not migrate the existing Paimon metadata/data from the old path to the new one.

The current check only rejects changing paimon.path while table.datalake.enabled is true. However, a table can be enabled once, then disabled later, while the Paimon table still exists. In that state, altering paimon.path would still be allowed. Could we make paimon.path a create-time-only option, or reject changing it once the lake table has ever been created?

Thanks for the review! Good catch. I’ll update the implementation accordingly.

[wzx140]

@luoyuxia I’ve updated the implementation to reject changes to paimon.path once the lake table has been created. Could you please review it again?