Re: SEARCH and CYCLE clauses

On 2020-10-10 07:25, Pavel Stehule wrote:
> This patch is based on transformation CYCLE and SEARCH clauses to 
> specific expressions - it is in agreement with ANSI SQL
> 
> There is not a problem with compilation
> Nobody had objections in discussion
> There are enough regress tests and documentation
> check-world passed
> doc build passed
> 
> I'll mark this patch as ready for committer
> 
> Possible enhancing for this feature (can be done in next steps)
> 
> 1. support UNION DISTINCT
> 2. better compatibility with Oracle and DB2 (USING clause can be optional)

Here is an updated patch.  New since last time:

- UNION DISTINCT is now supported (since hash_record() was added)

- Some code has been cleaned up.

- Some code has been moved from the rewriter to the parser so that 
certain errors are properly detected at parse time.

- Added more syntax checks and more tests.

- Support for dependency tracking was added (the type and operator for 
the cycle mark need to be added as dependencies).

I found a bug that nested UNIONs (foo UNION bar UNION baz) were not 
handled (would crash) in the rewriter code.  For now, I have just 
changed that to error out.  This could be fixed, it would be a localized 
change in the rewriter code in any case.  Doesn't seem important for the 
first pass, though.

-- 
Peter Eisentraut
2ndQuadrant, an EDB company
https://www.2ndquadrant.com/