thanos-io/thanos · error

get index version

Error message

get index version

What it means

Wraps IndexReader.IndexVersion failure in blockSeriesClient.series preloading. The store reads the index format version to decide whether expanded-posting counts need scaling (v2 hash-based posting encoding). Failure means the index version could not be fetched from the block's index reader.

Solutions

1. Delete and rebuild the block's index-header (remove the .index-header file; the store regenerates it).
2. Check the wrapped root error for object-store connectivity issues and retry.
3. Confirm the block's Prometheus/thanos index is a supported version (>= 1); re-compact or re-upload blocks from unsupported versions.
4. As a workaround, disable lazy expanded postings (store.lazy-expanded-posting-enabled=false) to skip this code path.

if err := query(ctx); err != nil && strings.Contains(err.Error(), "get index version") {
	// likely stale/corrupt index-header: trigger rebuild, then retry once
	rebuildIndexHeader(blockID)
	if err := query(ctx); err != nil {
		return fmt.Errorf("query failed after index-header rebuild: %w", err)
	}
}

When it happens

Trigger: Lazy expanded postings are enabled and non-empty (lazyExpandedPosting true with len(lazyPostings.postings) > 0), and b.indexr.IndexVersion() errors while fetching/decoding the index version from the block's index-header or index.

Common situations: Blocks written by very old Prometheus versions lacking version metadata, corrupted index-header, object-store errors while fetching index metadata during a lazy-postings query path.

Understand the failure class

Background: Database query failed: Internal Server Error 500s wrapping SQL, Prisma, and connection failures — what to check first — this error's family across 16 libraries.

Related errors

• preload series
• Lookup labels symbols
• label names for block
• input block index not valid
• output block index not valid

AI-assisted analysis of thanos-io/thanos@35b8b99117 (2026-09-07). Data as JSON: /api/errors/db19ed64e2d6a740. Report an issue: GitHub.

Appendix: source

Thrown at pkg/store/bucket.go:1287

		Chunks: next.chks,
	}), nil
}

func (b *blockSeriesClient) nextBatch(tenant string) error {
	start := b.i
	end := min(start+uint64(b.batchSize), uint64(len(b.lazyPostings.postings)))
	b.i = end

	lazyExpandedPosting := b.lazyPostings.lazyExpanded()
	postingsBatch := b.lazyPostings.postings[start:end]
	if len(postingsBatch) == 0 {
		b.hasMorePostings = false
		if lazyExpandedPosting {
			// No need to fetch index version again if lazy posting has 0 length.
			if len(b.lazyPostings.postings) > 0 {
				v, err := b.indexr.IndexVersion()
				if err != nil {
					return errors.Wrap(err, "get index version")
				}
				if v >= 2 {
					for i := range b.expandedPostings {
						b.expandedPostings[i] = b.expandedPostings[i] / 16
					}
				}
			}
			b.indexr.storeExpandedPostingsToCache(b.blockMatchers, index.NewListPostings(b.expandedPostings), len(b.expandedPostings), tenant)
		}
		return nil
	}

	b.indexr.reset(len(postingsBatch))
	if !b.skipChunks {
		b.chunkr.reset()
	}

	if err := b.indexr.PreloadSeries(b.ctx, postingsBatch, b.bytesLimiter, b.tenant); err != nil {

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