Re: POC PATCH: copy from ... exceptions to: (was Re: VLDB Features)

Hi! Thank you for your work. Your patch looks better!

On 10.12.2023 13:32, jian he wrote:
> On Fri, Dec 8, 2023 at 3:09 PM Alena Rybakina<lena.ribackina@yandex.ru>  wrote:
>> Thank you for your work. Unfortunately, your code contained errors during the make installation:
>>
>> 'SAVEPOINT' after 'SAVE_ERROR' in unreserved_keyword list is misplaced
>> 'SAVEPOINT' after 'SAVE_ERROR' in bare_label_keyword list is misplaced
>> make[2]: *** [../../../src/Makefile.global:783: gram.c] Error 1
>> make[1]: *** [Makefile:131: parser/gram.h] Error 2
>> make[1]: *** Waiting for unfinished jobs....
>> make: *** [src/Makefile.global:383: submake-generated-headers] Error 2
>>
>> I have ubuntu 22.04 operation system.
>>
>> On 06.12.2023 13:47, jian he wrote:
>>
>> On Tue, Dec 5, 2023 at 6:07 PM Alena Rybakina<lena.ribackina@yandex.ru>  wrote:
>>
>> Hi!
>>
>> Thank you for your contribution to this thread.
>>
>>
>> I reviewed it and have a few questions.
>>
>> 1. I have seen that you delete a table before creating it, to which you want to add errors due to a failed "copy from" operation. I think this is wrong because this table can save useful data for the user.
>> At a minimum, we should warn the user about this, but I think we can just add some number at the end of the name, such as name_table1, name_table_2.
>>
>> Sorry. I don't understand this part.
>> Currently, if the error table name already exists, then the copy will
>> fail, an error will be reported.
>> I try to first create a table, if no error then the error table will be dropped.
>>
>> To be honest, first of all, I misunderstood this part of the code. Now I see that it works the way you mentioned.
>>
>> However, I didn't see if you dealt with cases where we already had a table with the same name as the table error.
>> I mean, when is he trying to create for the first time, or will we never be able to face such a problem?
>>
>> Can you demo the expected behavior?
>>
>> Unfortunately, I was unable to launch it due to a build issue.
>>
> Hopefully attached will work.

Yes, thank you! It works fine, and I see that the regression tests have 
been passed. 🙂


However, when I ran 'copy from with save_error' operation with simple 
csv files (copy_test.csv, copy_test1.csv) for tables test, test1 (how I 
created it, I described below):

postgres=# create table test (x int primary key, y int not null);
postgres=# create table test1 (x int, z int, CONSTRAINT fk_x
       FOREIGN KEY(x)
           REFERENCES test(x));

I did not find a table with saved errors after operation, although I 
received a log about it:

postgres=# \copy test from '/home/alena/copy_test.csv' DELIMITER ',' CSV 
save_error
NOTICE:  2 rows were skipped because of error. skipped row saved to 
table public.test_error
ERROR:  duplicate key value violates unique constraint "test_pkey"
DETAIL:  Key (x)=(2) already exists.
CONTEXT:  COPY test, line 3

postgres=# select * from public.test_error;
ERROR:  relation "public.test_error" does not exist
LINE 1: select * from public.test_error;

postgres=# \copy test1 from '/home/alena/copy_test1.csv' DELIMITER ',' 
CSV save_error
NOTICE:  2 rows were skipped because of error. skipped row saved to 
table public.test1_error
ERROR:  insert or update on table "test1" violates foreign key 
constraint "fk_x"
DETAIL:  Key (x)=(2) is not present in table "test".

postgres=# select * from public.test1_error;
ERROR:  relation "public.test1_error" does not exist
LINE 1: select * from public.test1_error;

Two lines were written correctly in the csv files, therefore they should 
have been added to the tables, but they were not added to the tables 
test and test1.

If I leave only the correct rows, everything works fine and the rows are 
added to the tables.

in copy_test.csv:

2,0

1,1

in copy_test1.csv:

2,0

2,1

1,1

postgres=# \copy test from '/home/alena/copy_test.csv' DELIMITER ',' CSV
COPY 2
postgres=# \copy test1 from '/home/alena/copy_test1.csv' DELIMITER ',' 
CSV save_error
NOTICE:  No error happened.Error holding table public.test1_error will 
be droped
COPY 3

Maybe I'm launching it the wrong way. If so, let me know about it.


I also notice interesting behavior if the table was previously created 
by the user. When I was creating an error_table before the 'copy from' 
operation,
I received a message saying that it is impossible to create a table with 
the same name (it is shown below) during the 'copy from' operation.
I think you should add information about this in the documentation, 
since this seems to be normal behavior to me.

postgres=# CREATE TABLE test_error (LINENO BIGINT, LINE TEXT,
FIELD TEXT, SOURCE TEXT, ERR_MESSAGE TEXT,
ERR_DETAIL TEXT, ERRORCODE TEXT);
CREATE TABLE
postgres=# \copy test from '/home/alena/copy_test.csv' DELIMITER ',' CSV 
save_error
ERROR:  Error save table public.test_error already exists. Cannot use it 
for COPY FROM error saving
>
>> 2. I noticed that you are forming a table name using the type of errors that prevent rows from being added during 'copy from' operation.
>> I think it would be better to use the name of the source file that was used while 'copy from' was running.
>> In addition, there may be several such files, it is also worth considering.
>>
>> Another column added.
>> now it looks like:
>>
>> SELECT * FROM save_error_csv_error;
>>   filename | lineno |                        line
>>   | field | source |                 err_message                 |
>> err_detail | errorcode
>> ----------+--------+----------------------------------------------------+-------+--------+---------------------------------------------+------------+-----------
>>   STDIN    |      1 | 2002    232     40      50      60      70
>> 80 | NULL  | NULL   | extra data after last expected column       |
>> NULL       | 22P04
>>   STDIN    |      1 | 2000    230     23
>>   | d     | NULL   | missing data for column "d"                 | NULL
>>        | 22P04
>>   STDIN    |      1 | z,,""
>>   | a     | z      | invalid input syntax for type integer: "z"  | NULL
>>        | 22P02
>>   STDIN    |      2 | \0,,
>>   | a     | \0     | invalid input syntax for type integer: "\0" | NULL
>>        | 22P02
>>
>> Yes, I see the "filename" column, and this will solve the problem, but "STDIN" is unclear to me.
> please see comment in struct CopyFromStateData:
> char    *filename; /* filename, or NULL for STDIN */
>
Yes, I can see that.

I haven't figured out how to fix it yet either.

>>   */
>>
>> Maybe we can rewrite it like this:
>>
>> /* Check, the err_nsp.error_rel table has already existed
>> * and if it is, check its column name and data types.
>>
> refactored.

Fine)

-- 
Regards,
Alena Rybakina
Postgres Professional:http://www.postgrespro.com
The Russian Postgres Company