The intersection algorithm made it possible for .seek(..) with values
lower than the current doc id, breaking the DocSet contract.
The fix removes the optimization that caused left.seek(..) to be replaced
by a simpler left.advance(..).
Simply doing so lead to a performance regression.
I therefore integrated that idea within SegmentPostings.seek.
We now attempt to check the next doc systematically on seek,
PROVIDED the block is already loaded.
Closes#2811
Co-authored-by: Paul Masurel <paul.masurel@datadoghq.com>
A bug was added with the `seek_into_the_danger_zone()` optimization
(Spotted and fixed by Stu)
The contract says seek_into_the_danger_zone returns true if do is part of the docset.
The blanket implementation goes like this.
```
let current_doc = self.doc();
if current_doc < target {
self.seek(target);
}
self.doc() == target
```
So it will return true if target is TERMINATED, where really TERMINATED does not belong to the docset.
The fix tries to clarify the contracts and fixes the intersection algorithm.
We observe a small but all over the board improvement in intersection performance.
---------
Co-authored-by: Stu Hood <stuhood@gmail.com>
Co-authored-by: Paul Masurel <paul.masurel@datadoghq.com>
* seek_exact + cost based intersection
Adds `seek_exact` and `cost` to `DocSet` for a more efficient intersection.
Unlike `seek`, `seek_exact` does not require the DocSet to advance to the next hit, if the target does not exist.
`cost` allows to address the different DocSet types and their cost
model and is used to determine the DocSet that drives the intersection.
E.g. fast field range queries may do a full scan. Phrase queries load the positions to check if a we have a hit.
They both have a higher cost than their size_hint would suggest.
Improves `size_hint` estimation for intersection and union, by having a
estimation based on random distribution with a co-location factor.
Refactor range query benchmark.
Closes#2531
*Future Work*
Implement `seek_exact` for BufferedUnionScorer and RangeDocSet (fast field range queries)
Evaluate replacing `seek` with `seek_exact` to reduce code complexity
* Apply suggestions from code review
Co-authored-by: Paul Masurel <paul@quickwit.io>
* add API contract verfication
* impl seek_exact on union
* rename seek_exact
* add mixed AND OR test, fix buffered_union
* Add a proptest of BooleanQuery. (#2690)
* fix build
* Increase the document count.
* fix merge conflict
* fix debug assert
* Fix compilation errors after rebase
- Remove duplicate proptest_boolean_query module
- Remove duplicate cost() method implementations
- Fix TopDocs API usage (add .order_by_score())
- Remove duplicate imports
- Remove unused variable assignments
---------
Co-authored-by: Paul Masurel <paul@quickwit.io>
Co-authored-by: Pascal Seitz <pascal.seitz@datadoghq.com>
Co-authored-by: Stu Hood <stuhood@gmail.com>
* query: add DocSet cost hint and use it for intersection ordering
- Add DocSet::cost()
- Use cost() instead of size_hint() to order scorers in intersect_scorers
This isolates cost-related changes without the new seek APIs from
PR #2538
* add comments
---------
Co-authored-by: Pascal Seitz <pascal.seitz@datadoghq.com>
go_to_first_doc was typically calling seek with a target smaller than
doc.
Since SegmentPostings typically do a linear search on the full block,
regardless of the current position, it could have our segment postings
go backward.
- Change in the DocSet and Scorer API. (@fulmicoton).
A freshly created DocSet point directly to their first doc. A sentinel value called TERMINATED marks the end of a DocSet.
`.advance()` returns the new DocId. `Scorer::skip(target)` has been replaced by `Scorer::seek(target)` and returns the resulting DocId.
As a result, iterating through DocSet now looks as follows
```rust
let mut doc = docset.doc();
while doc != TERMINATED {
// ...
doc = docset.advance();
}
```
The change made it possible to greatly simplify a lot of the docset's code.
- Misc internal optimization and introduction of the `Scorer::for_each_pruning` function. (@fulmicoton)
* Refactor deletes
* Removing generation from SegmentUpdater. These have been obsolete for a long time
* Number literal clippy
* Removed clippy useless allow statement
Paul Masurel
PSeitz
Bruce Mitchener
Paul Masurel
fdb-hiroshima