Pull Request resolves #48167 .

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

ChangeSet now tracks, per changed column or index, whether a later SQL update file changes the same schema object. Change items whose target has been redefined by a later file are flagged with a new ChangeItem::$superseded property.

ChangeSet::check() and ChangeSet::getStatus() no longer report a -2 (check failed) result as an error when the corresponding item is superseded — it is treated as skipped instead. This lets extensions keep a full history of incremental schema changes across versions (e.g. a column added in one release and altered in a later one) without Joomla reporting a false database error when the database already matches the latest definition, just not the older, superseded one.

ChangeItem::$queryType docblock also updated to list the current, complete set of supported query types (ADD_COLUMN, ADD_INDEX, CHANGE_COLUMN_TYPE, CREATE_TABLE, DROP_COLUMN, DROP_INDEX, RENAME_TABLE), replacing the outdated ADD_TABLE reference.

Only column-level (ADD_COLUMN, DROP_COLUMN, CHANGE_COLUMN_TYPE) and index-level (ADD_INDEX, DROP_INDEX) change items can be superseded, keyed by table + column/index name. CREATE_TABLE and RENAME_TABLE items are never superseded.

Testing Instructions

1. Create an extension (or use the sample one from the linked bug report) with multiple SQL update files where the same column is added in one file and its type changed in a later file, or an index is added and later dropped.
2. Install the extension at the earlier version, then update it through the later SQL files.
3. Run the "Database" page in System → System Information (or trigger ChangeSet::check()/getStatus() for the extension).
4. Confirm that the historical (superseded) change items no longer show up as database errors, while the current, non-superseded expectations are still checked normally.

Actual result BEFORE applying this Pull Request

Extensions whose SQL update files change the same column or index more than once across versions (e.g. add a column, then later change its type) are reported as having database errors, even though the database schema fully matches the extension's latest intended definition. The obsolete, superseded expectation from the earlier update file is still checked and fails.

Expected result AFTER applying this Pull Request

Change items superseded by a later update to the same column or index are no longer reported as errors (they are reported as skipped instead), while still being re-run by fix() when needed as an intermediate step. Only the current, non-superseded expectations are treated as errors when they fail.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

Further information

If accepted, this PR must be backport to 5.4-dev and forward-port to 6.2-dev. It is easy. The files seem identical in all three branches.