feat: allow a USING clause for alter table column type in postgres

[jpopesculian]

PR Info

• Closes (PG) Support ALTER COLUMN TYPE USING #626

• Dependencies:

• Dependents:

New Features

• Allows a USING clause for ALTER TABLE COLUMN TYPE

Bug Fixes

Breaking Changes

• This is backwards compatible

Changes

• Adds a Using variant to ColumnSpec

[billy1624]

Hey @jpopesculian, thanks for contributing!!

I think this is good to have! Any comments from @tyt2y3?

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Additional Context:

The optional USING clause specifies how to compute the new column value from the old; if omitted, the default conversion is the same as an assignment cast from old data type to new. A USING clause must be provided if there is no implicit or assignment cast from old to new type.

https://www.postgresql.org/docs/current/sql-altertable.html