Hi, I have progressed a bit with my pet project, a.k.a $SUBJECT.
Now GENERATED ALWAYS AS IDENTITY and GENERATED ALWAYS AS ( expr ) work as intended. Documentation was also extended. Some test cases are also included, that shows that ALTER TABLE ALTER TYPE keeps both the sequence and the GENERATED ALWAYS property. Gzipped patch is attached. Next steps are: - pg_dump support - more ALTER TABLE support for adding and dropping IDENTITY and GENERATED ALWAYS features - more testing I still maintain that I don't see any standard requirement between the GENERATED AS IDENTITY and NEXT VALUE FOR but obviously both require SEQUENCE as supported feature in parallel. I can be proven wrong, though, but please, quote section# and text where it can be found in the standard. As for why GENERATED ALWAYS AS IDENTITY is useful? Consider someone who is coming from another DBMS (Informix, Access, etc.) where "INSERT INTO table (id, ...) VALUES (0, ...);" inserts the next value for the autoincrementer field instead of 0. Leaving out fields from INSERT is not allowed in the source because of documentation reasons and writing DEFAULT is not handy or not found in that legacy DBMS' features. Multiply it with N applications that was written that way over the years of the lifespan of a large project, count in the human resistance to learn something new (say 2.5x multiplier, but that may be under-estimated :-) ) and a feature that help porting easier will be a cheered feature. IIRC Bruce Momjian himself wrote in this list that ease-of-use features can boost PostgreSQL userbase pretty quickly. So, please, review my patch in it's current state and decide whether it's a 8.2-worthy feature. BTW, is there anyone working on COPY FROM ( select ) feature? Thanks in advance and best regards, Zoltán Böszörményi
psql-serial-12.diff.gz
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
