On 2021/03/30 10:11, Kohei KaiGai wrote:
2021年3月30日(火) 3:45 Fujii Masao <masao.fu...@oss.nttdata.com>:
On 2021/03/28 2:37, Kazutaka Onishi wrote:
Fujii-san,
Thank you for your review!
Now I prepare v5 patch and I'll answer to your each comment. please
check this again.
m(_ _)m
1. In postgres-fdw.sgml, "and truncatable" should be appended into the
above first description?
2. truncate.sgml should be updated because, for example, it contains
the above descriptions.
Yeah, you're right. I've fixed it.
3. Don't we need to document the detail information about frels_extra?
I've written about frels_extra into fdwhander.sgml.
4. postgres_fdw determines whether to specify ONLY or not by checking
whether the passed extra value is zero or not.
Please refer this:
https://www.postgresql.org/message-id/CAOP8fzb-t3WVNLjGMC%2B4sV4AZa9S%3DMAQ7Q6pQoADMCf_1jp4ew%40mail.gmail.com
Negative value means that foreign-tables are not specified in the TRUNCATE
command, but truncated due to dependency (like partition's child leaf).
I've added this information into fdwhandler.sgml.
Even when a foreign table is specified explicitly in TRUNCATE command,
its extra value can be negative if it's found as an inherited children firstly
(i.e., in the case where the partitioned table having that foreign table as
its partition is specified explicitly in TRUNCATE command).
Isn't this a problem?
Please imagine the following example;
----------------------------------
create extension postgres_fdw;
create server loopback foreign data wrapper postgres_fdw;
create user mapping for public server loopback;
create table t (i int, j int) partition by hash (j);
create table t0 partition of t for values with (modulus 2, remainder 0);
create table t1 partition of t for values with (modulus 2, remainder 1);
create table test (i int, j int) partition by hash (i);
create table test0 partition of test for values with (modulus 2, remainder 0);
create foreign table ft partition of test for values with (modulus 2, remainder
1) server loopback options (table_name 't');
----------------------------------
In this example, "truncate ft, test" works fine, but "truncate test, ft" causes
an error though they should work in the same way basically.
(Although it was originally designed by me...)
If frels_extra would be a bit-masked value, we can avoid the problem.
Please assume the three labels below:
#define TRUNCATE_REL_CONTEXT__NORMAL 0x01
#define TRUNCATE_REL_CONTEXT__ONLY 0x02
#define TRUNCATE_REL_CONTEXT__CASCADED 0x04
Then, assign these labels on the extra flag according to the context where
the foreign-tables appeared in the truncate command.
Even if it is specified multiple times in the different context, FDW extension
can handle the best option according to the flags.
In this example, "truncate ft, test" works fine, but "truncate test, ft" causes
In both cases, ExecForeignTruncate shall be invoked to "ft" with
(NORMAL | CASCADED),
thus, postgres_fdw can determine the remote truncate command shall be
executed without "ONLY" clause.
How about the idea?
This idea looks better to me.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
