Re: Emitting JSON to file using COPY TO
От | Joe Conway |
---|---|
Тема | Re: Emitting JSON to file using COPY TO |
Дата | |
Msg-id | cb1f118c-4698-4451-9ba9-dd8595f06c37@joeconway.com обсуждение исходный текст |
Ответ на | Re: Emitting JSON to file using COPY TO (Andrew Dunstan <andrew@dunslane.net>) |
Ответы |
Re: Emitting JSON to file using COPY TO
(Joe Conway <mail@joeconway.com>)
Re: Emitting JSON to file using COPY TO (Andrew Dunstan <andrew@dunslane.net>) |
Список | pgsql-hackers |
On 12/5/23 15:55, Andrew Dunstan wrote: > > On 2023-12-05 Tu 14:50, Davin Shearer wrote: >> Hi Joe, >> >> In reviewing the 005 patch, I think that when used with FORCE ARRAY, >> we should also _imply_ FORCE ROW DELIMITER. I can't envision a use >> case where someone would want to use FORCE ARRAY without also using >> FORCE ROW DELIMITER. I can, however, envision a use case where >> someone would want FORCE ROW DELIMITER without FORCE ARRAY, like maybe >> including into a larger array. I definitely appreciate these options >> and the flexibility that they afford from a user perspective. >> >> In the test output, will you also show the different variations with >> FORCE ARRAY and FORCE ROW DELIMITER => {(false, false), (true, false), >> (false, true), (true, true)}? Technically you've already shown me the >> (false, false) case as those are the defaults. >> >> > > I don't understand the point of FORCE_ROW_DELIMITER at all. There is > only one legal delimiter of array items in JSON, and that's a comma. > There's no alternative and it's not optional. So in the array case you > MUST have commas and in any other case (e.g. LINES) I can't see why you > would have them. The current patch already *does* imply row delimiters in the array case. It says so here: 8<--------------------------- + <varlistentry> + <term><literal>FORCE_ARRAY</literal></term> + <listitem> + <para> + Force output of array decorations at the beginning and end of output. + This option implies the <literal>FORCE_ROW_DELIMITER</literal> + option. It is allowed only in <command>COPY TO</command>, and only + when using <literal>JSON</literal> format. + The default is <literal>false</literal>. + </para> 8<--------------------------- and it does so here: 8<--------------------------- + if (opts_out->force_array) + opts_out->force_row_delimiter = true; 8<--------------------------- and it shows that here: 8<--------------------------- + copy copytest to stdout (format json, force_array); + [ + {"style":"DOS","test":"abc\r\ndef","filler":1} + ,{"style":"Unix","test":"abc\ndef","filler":2} + ,{"style":"Mac","test":"abc\rdef","filler":3} + ,{"style":"esc\\ape","test":"a\\r\\\r\\\n\\nb","filler":4} + ] 8<--------------------------- It also does not allow explicitly setting row delimiters false while force_array is true here: 8<--------------------------- + if (opts_out->force_array && + force_row_delimiter_specified && + !opts_out->force_row_delimiter) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("cannot specify FORCE_ROW_DELIMITER false with FORCE_ARRAY true"))); 8<--------------------------- Am I understanding something incorrectly? -- Joe Conway PostgreSQL Contributors Team RDS Open Source Databases Amazon Web Services: https://aws.amazon.com
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