1202526 - Add to PLDHashTable the ability to remove an already-found entry

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Nicholas Nethercote [inactive]]

(This is a slightly modified version of bug 848609.)

A very common use case for a hash table is this:

(1) lookup item
(2) do something with it
(3) remove it

With pldhash, for step (3) you either have to Remove(), which repeats the search, or use RawRemove(), which does not subsequently shrink the table if its capacity gets too low.

This bug is about adding a new function that takes an already found entry (like RawRemove()) but also shrinks the table afterwards if appropriate (like Remove()). And then using it when appropriate.

Comment 1

[Nicholas Nethercote [inactive]]

Attachment: (part 1) - Add PLDHashTable::RemoveEntry()

This patch also consolidates the shrink handling so it's now entirely within
ShrinkIfAppropriate().

Comment 2

[Nicholas Nethercote [inactive]]

Attachment: (part 2) - Avoid PL_DHashTableRawRemove() in nsLoadGroup

This assumes that it's safe to possibly shrink the table after the removal,
i.e. there are no surprising subtleties with how this table is managed.

Comment 3

[Nicholas Nethercote [inactive]]

Attachment: (part 3) - Avoid PL_DHashTableRawRemove() in nsDocument

This assumes that it's safe to possibly shrink the table after the removal,
i.e. there are no surprising subtleties with how this table is managed.

Comment 4

[Nicholas Nethercote [inactive]]

Attachment: (part 4) - Avoid PL_DHashTableRawRemove() in nsPropertyTable

This assumes that it's safe to possibly shrink the table after the removal,
i.e. there are no surprising subtleties with how this table is managed.

Comment 5

[Nicholas Nethercote [inactive]]

Attachment: (part 5) - Use PLDHashTable::RemoveEntry() in nsSecureBrowserUIImpl

This avoids repeating the hash table search in order to remove the entry.

Comment 6

[Nicholas Nethercote [inactive]]

Attachment: (part 6) - Use PLDHashTable::RemoveEntry() in XULDocument

This avoids repeating the hash table search in order to remove the entry.

Comment 7

[Nicholas Nethercote [inactive]]

Attachment: (part 7) - Use PLDHashTable::RemoveEntry() in prefs code

This avoids repeating the hash table search in order to remove the entry.

Comment 8

[Nicholas Nethercote [inactive]]

Attachment: (part 8) - Use PLDHashTable::RemoveEntry() in the cycle collector

This avoids repeating the hash table search in order to remove a CC graph
entry, which is good because it's a common operation.

Comment 9

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8658011 [details] [diff] [review]
(part 3) - Avoid PL_DHashTableRawRemove() in nsDocument

r=me

Comment 10

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8658012 [details] [diff] [review]
(part 4) - Avoid PL_DHashTableRawRemove() in nsPropertyTable

r=me

Comment 11

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8658015 [details] [diff] [review]
(part 6) - Use PLDHashTable::RemoveEntry() in XULDocument

r=me

Comment 12

[Nicholas Nethercote [inactive]]

Try looks good: https://treeherder.mozilla.org/#/jobs?repo=try&revision=cda97f7f4516

(Ignore all the red W tests in that push. There was some problem with them when I did the push.)

Comment 13

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/6d21d79e8abb
https://hg.mozilla.org/integration/mozilla-inbound/rev/19103f4ad55d
https://hg.mozilla.org/integration/mozilla-inbound/rev/59fea40ba289
https://hg.mozilla.org/integration/mozilla-inbound/rev/438b7e68c23a
https://hg.mozilla.org/integration/mozilla-inbound/rev/aa827e8bdba2
https://hg.mozilla.org/integration/mozilla-inbound/rev/38e1c1c1bdc7
https://hg.mozilla.org/integration/mozilla-inbound/rev/1ff0bf051b24
https://hg.mozilla.org/integration/mozilla-inbound/rev/2afc19650063

Comment 14

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/6d21d79e8abb
https://hg.mozilla.org/mozilla-central/rev/19103f4ad55d
https://hg.mozilla.org/mozilla-central/rev/59fea40ba289
https://hg.mozilla.org/mozilla-central/rev/438b7e68c23a
https://hg.mozilla.org/mozilla-central/rev/aa827e8bdba2
https://hg.mozilla.org/mozilla-central/rev/38e1c1c1bdc7
https://hg.mozilla.org/mozilla-central/rev/1ff0bf051b24
https://hg.mozilla.org/mozilla-central/rev/2afc19650063