Label matchers (equal, not-equal, regexp, not-regexp) in labels/,
postings intersection/union/difference in internal/postings/,
LabelValues and AllPostings on index, block, and head readers.
ingot.go wired to real DB backed by head + block readers. Querier
snapshots overlapping blocks, Select resolves matchers to postings,
merged iterator chains blocks then head with block-wins dedup.
Oracle tests compare every query against a naive []sample reference
across head-only, block-only, head+block merge seam, multiple blocks,
all four matcher types, and time range filtering.
Flush sealed head chunks to ULID-named block directories on disk. Each
block contains CRC'd chunk segment files (mmap'd for reads), a binary
index (symbol table, series, postings with TOC), and a meta.json written
last as the immutability gate. WAL is truncated after block fsync,
preserving the crash-safety ording invariant.
david