Is it possible to seek to the first key less than a given key about leveldb HOT 5 CLOSED

Comment #1 originally posted by john.carrino on 2011-08-13T19:18:34.000Z:

Actually I realized there is an iterator snapshot operation. This will work for me in this case. Do you know the performance penalty of using a snapshot?

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Comment #2 originally posted by [email protected] on 2011-08-15T00:19:00.000Z:

Hi John, thanks a lot for your tests.

We'd like to patch these tests into LevelDB code's - do you mind filling out this CLA so we can patch it in?
http://code.google.com/legal/individual-cla-v1.0.html
Let me know when you've completed this.

Thanks for your help,

Gabor

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Comment #3 originally posted by david.yu.ftw on 2011-08-15T05:55:05.000Z:

"I would like to find the first key that is less than a given key. I can only think of two ways to achieve this goal and they both fail.

1. seek to key then go back one. This fails because if the key you want is the last key, then you have an invalid iterator and you get a segfault."

I've the same use-case but I solved # 1 by adding a definite last key as a marker. This key is checked on database startup ... and initialized if database is new.
Its possible if your keys are predictable (I used 0xFFFF as the exclusive last key).

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Comment #4 originally posted by [email protected] on 2011-08-22T20:55:38.000Z:

This should be fixed in R48 - please verify!

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I've run into the same issue re Prev on an "end" iterator (when Seek runs past the last key).

I tried John's tests on the latest code in master (7035af5) and they both fail there.

On ab323f7, which was supposed to fix this issue, IterSnapshotViewSeekToEnd passes, but not IterPastEndThenPrev.

I currently have to use the dummy key approach suggested by David to get around it.

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