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Allow an alias to be attached to a JOIN ... USING

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This allows something like

    SELECT ... FROM t1 JOIN t2 USING (a, b, c) AS x

where x has the columns a, b, c and unlike a regular alias it does not
hide the range variables of the tables being joined t1 and t2.

Per SQL:2016 feature F404 "Range variable for common column names".

Reviewed-by: Vik Fearing <vik.fearing@2ndquadrant.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/454638cf-d563-ab76-a585-2564428062af@2ndquadrant.com
This commit is contained in:
Peter Eisentraut
2021-03-31 17:09:24 +02:00
parent 27e1f14563
commit 055fee7eb4
22 changed files with 315 additions and 29 deletions
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5
src/include/parser/parse_node.h
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@@ -228,7 +228,10 @@ struct ParseState
* An element of a namespace list.
*
* p_names contains the table name and column names exposed by this nsitem.
* (Currently, it's always equal to p_rte->eref.)
* (Typically it's equal to p_rte->eref, but for a JOIN USING alias it's
* equal to p_rte->join_using_alias. Since the USING columns will be the
* join's first N columns, the net effect is just that we expose only those
* join columns via this nsitem.)
*
* p_rte and p_rtindex link to the underlying rangetable entry.
*