[Libreoffice-bugs] [Bug 136838] New: AutoFilter Improvement: Use "Not Equal" (i.e., <>) when we selected all but one item

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=136838

            Bug ID: 136838
           Summary: AutoFilter Improvement: Use "Not Equal" (i.e., <>)
                    when we selected all but one item
           Product: LibreOffice
           Version: 6.4.6.2 release
          Hardware: All
                OS: Linux (All)
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: medium
         Component: Calc
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: suokunlong at 126.com

Created attachment 165612
  --> https://bugs.documentfoundation.org/attachment.cgi?id=165612&action=edit
test ODS file with autofilter

Assume a column contains n items. When we open the autofilter and un-selected
one, then we have n-1 items selected. Doing this filter with AutoFilter is slow
because it seems to be using the "x in n-1" logic. However, doing this filter
with Standard Filter is fast if we use "Not Equal" logic.

Steps to Reproduce:

1. Open the attached test ODS file

2. Click the autofilter in column A, and de-select the 1st item (i.e., #N/A),
then click OK.
--> Slow, it takes more than 8s.

3. Use Standard Filter, and set condition "POMatch <> #N/A", then click OK.
--> Fast, it takes 1s.

Apparently, if we deselect only one item, the condition is the same as <> that
item. It should be more expensive to compare the value to see whether it is in
the n-1 list.

Actually, if we de-select several items (e.g., 3 items), it would still be
faster to use "(x <> a) and (x <> b) and (x <> c)". However, if the deselected
items are quite a lot, the "x in n-1" logic should be faster.

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