On 2016/07/29 13:28, Ashutosh Bapat wrote:
I wrote:
Probably something like this:
Foreign Processing
Remote Operations: ...
In the Remote Operations line, the FDW/extension could print
any info
about remote operations, eg, "Scan/Join + Aggregate".
I wrote:
I intentionally chose that word and thought we could leave detailed
descriptions about remote operations to the FDW/extension; a broader
word like "Processing" seems to work well because we allow various
kinds of operations to the remote side, in addition to scans/joins,
to be performed in that one Foreign Scan node indicated by "Foreign
Processing", such as aggregation, window functions, distinct, order
by, row locking, table modification, or combinations of them.
"Scan" is a better word than "Processing". From plan's perspective it's
ultimately a Scan (on the data produced by the foreign server) and not
processing.
Exactly, but one thing I'm concerned about is the table modification
case; the EXPLAIN output would be something like this:
Foreign Scan
Remote SQL: INSERT INTO remote_table VALUES ...
That would be strange, so I think a more broader word is better. I
don't think "Foreign Processing" is best. "Foreign Upper" might be much
better because the corresponding path is created by calling
GetForeignUpperPaths.
Also for a Foreign Scan representing a foreign join, I think "Foreign
Join" is better than "Foreign Scan". Here is an example:
Foreign Join on foreign_table1, foreign_table2
Remote SQL: SELECT ... FROM remote_table1 INNER JOIN remote_table2
WHERE ...
I think "Foreign Join" better indicates that foreign tables listed after
that (ie, foreign_table1 and foreign_table2 in the example) are joining
(or component) tables of this join, than "Foreign Scan".
Best regards,
Etsuro Fujita
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