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c7b2210ac3
tsdb: cache collected head chunks on ChunkReader for O(1) lookup The query path calls s.chunk() once per chunk meta via ChunkOrIterableWithCopy. Each call walks the head chunks linked list from the head to the target position. For a series with N head chunks iterated oldest-first, total work is O(N²). Cache the collected []*memChunk slice on headChunkReader, keyed by series ref, head pointer, and mmapped chunks length. Collected once per series under lock; reused on subsequent chunk lookups for the same series. The backing array is reused across series (zero alloc after first use). Series with 0 or 1 head chunks skip the cache entirely to avoid per-series overhead that dominates for typical workloads where most series have a single head chunk. The cache is gated behind an enableCache flag, toggled via an optional chunkCacheToggler interface only when hints.Step > 0 (range queries). Instant queries only need one chunk per series, so the cache overhead is not recouped. Also replace O(N²) linked-list traversals in appendSeriesChunks with O(N) collectHeadChunks + slice iteration, and thread reusable headChunksBuf through the index reader paths to avoid per-series allocations. --------- Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com> Co-authored-by: George Krajcsovits <krajorama@users.noreply.github.com>
TSDB
This directory contains the Prometheus TSDB (Time Series DataBase) library, which handles storage and querying of all Prometheus v2 data.
Documentation
External resources
- A writeup of the original design can be found here.
- Video: Storing 16 Bytes at Scale from PromCon 2017.
- Compression is based on the Gorilla TSDB white paper.
A series of blog posts explaining different components of TSDB: