Re: COPY FROM WHEN condition

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От Alvaro Herrera
Тема Re: COPY FROM WHEN condition
Дата
Msg-id 20181204094418.wpr6mxrtsuxb5mlq@alvherre.pgsql
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Ответ на Re: COPY FROM WHEN condition  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Ответы Re: COPY FROM WHEN condition  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Re: COPY FROM WHEN condition  (Surafel Temesgen <surafel3000@gmail.com>)
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After reading this thread, I think I like WHERE better than FILTER.
Tally:

WHERE: Adam Berlin, Lim Myungkyu, Dean Rasheed, yours truly
FILTER: Tomas Vondra, Surafel Temesgen

Couldn't find others expressing an opinion in this regard.

On 2018-Nov-30, Tomas Vondra wrote:

> I think it should be enough just to switch to CIM_SINGLE and increment the
> command counter after each inserted row.

Do we apply command counter increment per row with some other COPY
option?  Per-row CCI makes me a bit uncomfortable because with you'd get
in trouble with a large copy.  I think it's particularly nasty here,
precisely because you may want to filter out some rows of a very large
file, and the CCI may prevent that from working.
I'm not convinced by the example case of reading how many tuples you've
imported so far in the WHERE/WHEN/FILTER clause each time (that'd become
incrementally slower as it progresses).

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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