Re: [PERFORM] EXTERNAL storage and substring on long strings

От: Tom Lane
Тема: Re: [PERFORM] EXTERNAL storage and substring on long strings
Дата: ,
Msg-id: 6311.1060884021@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Re: [PERFORM] EXTERNAL storage and substring on long strings  (Jan Wieck)
Ответы: Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain)
Re: [PERFORM] EXTERNAL storage and substring on long strings  (Jan Wieck)
Список: pgsql-sql

Скрыть дерево обсуждения

Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain, )
 Re: [PERFORM] EXTERNAL storage and substring on long strings  (Tom Lane, )
  Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain, )
   Re: [PERFORM] EXTERNAL storage and substring on long strings  (Joe Conway, )
    Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain, )
     Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain, )
      Re: [PERFORM] EXTERNAL storage and substring on long strings  (Joe Conway, )
  Re: [PERFORM] EXTERNAL storage and substring on long strings  (Jan Wieck, )
   Re: [PERFORM] EXTERNAL storage and substring on long strings  (Tom Lane, )
    Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain, )
    Re: [PERFORM] EXTERNAL storage and substring on long strings  (Jan Wieck, )
 Re: [PERFORM] EXTERNAL storage and substring on long strings  (Richard Huxton, )
  Re: [PERFORM] EXTERNAL storage and substring on long strings  (Scott Cain, )
   Re: [PERFORM] EXTERNAL storage and substring on long strings  ("Matt Clark", )
   Re: [PERFORM] EXTERNAL storage and substring on long strings  ("Shridhar Daithankar", )

Jan Wieck <> writes:
> Doesn't look that unrealistic to me. A plain text based substring
> function will reassemble the whole beast first before cutting out the
> wanted part. His manually chunked version will read only those chunks
> needed.

So does substr(), if applied to EXTERNAL (non-compressed) toasted text.
See John Gray's improvements a release or two back.

            regards, tom lane


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