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fix(alter): keep an attribute's values when alter() renames it (2.3) - #1635
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`alter()` renames an attribute whose new comment opens with `{old_name}`. It looked for that marker in the compiled column SQL, where it is not always found. A core type or codec writes its `:type:` marker in front of the comment (`COMMENT ":float32:{value} ..."`), and PostgreSQL keeps comments out of the column SQL altogether. In both cases the rename went unnoticed: `alter()` dropped the old attribute and added the new one, and every value was lost. On MySQL, renaming `value : float32` to `reading : float32 # {value}` left `reading` at 0.0 in every row; on PostgreSQL, renaming a nullable attribute left it NULL. A required attribute on PostgreSQL failed with a NOT NULL error instead.
The marker is now read from the comment as declared, after any `:type:` marker. On MySQL the rename becomes a CHANGE, which keeps the values. PostgreSQL has no CHANGE, so `alter()` now refuses a rename there with a DataJointError before running anything, instead of dropping the attribute.
The new tests rename a required and a nullable core-type attribute of a table holding rows. On MySQL they check that the values survive; on PostgreSQL that the rename is refused and the table keeps its values. All four fail before this change.
(cherry picked from commit 6657b23)
dimitri-yatsenko
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MilagrosMarin,
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ttngu207
October 18, 2026 00:30
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Backport of #1634 to
maint/2.3for v2.3.5, cherry-picked unchanged.alter()renames an attribute whose new comment opens with{old_name}. It looked for that marker in the compiled column SQL, where it is not always found. A core type or codec writes its:type:marker in front of the comment (COMMENT ":float32:{value} ..."), and PostgreSQL keeps comments out of the column SQL altogether. In both cases the rename went unnoticed:alter()dropped the old attribute and added the new one, and every value was lost. On MySQL, renamingvalue : float32toreading : float32 # {value}leftreadingat 0.0 in every row; on PostgreSQL, renaming a nullable attribute left it NULL. A required attribute on PostgreSQL failed with a NOT NULL error instead.The marker is now read from the comment as declared, after any
:type:marker. On MySQL the rename becomes a CHANGE, which keeps the values. PostgreSQL has no CHANGE, soalter()now refuses a rename there with a DataJointError before running anything, instead of dropping the attribute.The new tests rename a required and a nullable core-type attribute of a table holding rows. On MySQL they check that the values survive; on PostgreSQL that the rename is refused and the table keeps its values. All four fail before this change.
Fixes #1631.