[bug #68149] sqlite very slow on large fetch due to buffer resize bug

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URL:
  <https://savannah.gnu.org/bugs/?68149>

                 Summary: sqlite very slow on large fetch due to buffer resize
bug
                   Group: GNU Octave
               Submitter: rot26
               Submitted: Thu 12 Mar 2026 04:59:55 AM UTC
                Category: Octave Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name:
        Originator Email:
             Open/Closed: Open
         Discussion Lock: Unlocked
                 Release: other
        Operating System: GNU/Linux
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Thu 12 Mar 2026 04:59:55 AM UTC By: rot26 <rot26>
Octave Sqlite becomes progressively slower to fetch per row, as the number of
rows in the result set increases  -to the point where it quickly becomes
unworkable. 

The problem appears to be that the size of the vector collecting records is
increased by a small constant factor (20 rows) only. 

Doubling the size of this buffer, every time it proves too small seems extreme
but works well (eg on a million rows) and is afaik common practice, when the
ultimate requirement is unknown  -and this may well have been the author's
original intent.

The proposed patch attached, also adds 20 to avoid a resize to 0 on the first
pass, so behaviour for very small fetches will be unchanged.








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File Attachments:

Name: octave_sqlite.cc.diff          Size: 140B
    <https://file.savannah.gnu.org/file/octave_sqlite.cc.diff?file_id=58348>



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