To cope with writing large files out of order, the system needs some form of strategy to avoid writing them directly to disk, as this causes insane amounts of disk thrashing. By default, the data is just buffered in RAM. This works well on a large server, but smaller systems struggle.
To help systems with small RAM process large amounts of data, the old RandomWriteFunnel is brought back if the system property 'system.conserve-memory' is set to true. RandomWriteFunnel is buffering the construction by creating a series of small files that pigeonhole the writes into rough neighborhoods, and then it goes over the files one by one to construct one area of the file at a time. This is relatively slow and uses more than twice the disk size.
A new interface RandomFileAssembler is introduced as an abstraction for this operation. A third strategy, direct mmaps, is also introduced if the file is very small (less than 1 GB). In this domain, disk thrashing is unlikely since it will comfortably fit in RAM.
This was caused by a bug in the binary search algorithm causing it to sometimes return positive values when encoding a search miss.
It was also necessary to get rid of the vestiges of the old LongArray and IntArray classes to make this fix doable.
* (index-reverse) Parallel construction of the reverse indexes.
* (array) Remove wasteful calculation of numDistinct before merging two sorted arrays.
* (index-reverse) Force changes to disk on close, reduce logging.
* (index-reverse) Clean up merging process and add back logging
* (run) Add a conservative default for INDEX_CONSTRUCTION_PROCESS_OPTS's parallelism as it eats a lot of RAM
* (index-reverse) Better logging during processing
* (array) 2GB+ compatible write() function
* (array) 2GB+ compatible write() function
* (index-reverse) We are logging like Bolsonaro and I will not have it.
* (reverse-index) Self-diagnostics
* (btree) Fix bug in btree reader to do with large data sizes
Further de-ByteBuffer:ing of these classes is to be done, but this is the smallest most urgently needed benefit.
This commit is a WIP but in a fully working state, pushing due to the importance of the changes to offer lifecycle control over mmaps.
... also move some common configuration into the root build.gradle-file.
Support for JDK21 in lombok is a bit sketchy at the moment, but it seems to work. This upgrade is kind of important as the new index construction really benefits from Arena based lifecycle control over off-heap memory.
This is a system-wide change. The index used to have a lexicon, mapping words to wordIds using a large in-memory hash table. This made index-construction easier, but it
also added a fairly significant RAM penalty to both the index service and the loader.
The new design moves to 64 bit word identifiers calculated using the murmur hash of the keyword, and an index construction based on merging smaller indices.
It also became necessary half-way through to upgrade guice as its error reporting wasn't *quite* compatible with JDK20.
This provides a much cleaner separation of concerns, and makes it possible to get rid of a lot of the gunkier parts of the index service. It will also permit lowering the Xmx on the index service a fair bit, so we can get CompressedOOps again :D
* Increase accuracy of the position bits.
* Increase their width to 56.
* Use a rolling position scheme for bits 16-56 to increase the average accuracy.
* Result ranking overhaul
* Optimized queries
* BM25 in the index service's ranking
* Make gui less jank
* Javadocs for ranking parameters.
* A deduplication filter step ran too early, and removed many good results on the basis that they partially, but did not fully fit another set of search terms.
* Altered the query creation process to prefer documents where multiple terms appear in the priority index.
