*: Phases 3+4 — drop FrostDB-backed tests, rip frostdb out of go.mod

[thorfour]

Summary

Final phases of the FrostDB removal. Stacks on #6355 (Phase 2.B). Net diff: -22,759 lines.

Combined into one PR because the schema-proto removal that unblocks dropping frostdb from go.mod is part of the test/cleanup work.

Strategy (option C from the Phase 3 triage)

The FrostDB-backed tests aren't testing the new ClickHouse path — they're exercising a backend that's about to be deleted. Their carry-forward value is debatable, and a fresh ClickHouse-targeted integration test (using testcontainers, alongside the existing pkg/clickhouse/filter_test.go) is more honest than a port. Filed as a follow-up.

Deleted

• pkg/ingester/ — the FrostDB-only TableIngester. The tiny Ingester interface that ProfileColumnStore consumes moved to pkg/profilestore.
• pkg/parcacol/querier.go — the FrostDB-only querier. ClickHouse has its own (pkg/clickhouse/querier.go).
• pkg/parca/parca_test.go — TestPGOE2e, TestLabels, TestConsistency (already t.Skip'd), Benchmark_WriteRaw (already b.Skip'd). All spun up a real frostdb columnstore.
• pkg/profilestore/profilestore_test.go — both tests were frostdb-backed.
• pkg/query/query_test.go — both benchmarks were frostdb-backed.
• The 9 frostdb-backed tests in pkg/query/columnquery_test.go (TestColumnQueryAPI*). The remaining filter / merge / utility tests are kept along with helper functions (MustReadAllGzip etc.) that other test files in the package depend on.
• profile.Schema() — the function returning *dynparquet.Schema.

Reshaped

• pkg/profile/schema.go: SchemaDefinition() now returns a small local SchemaDef struct instead of *schemapb.Schema. The proto-defined encoding/compression/sorting hints are dropped — they were only consumed by the parquet writer. The few fields actually read at runtime (Name, Type, Repeated, Nullable, Dynamic) survive on a hand-rolled struct. This severs the last frostdb proto import.
• pkg/profilestore: gains a thin Ingester interface (same shape pkg/ingester defined).
• pkg/query/sources_test.go: parcacol.NewQuerier is gone, so the source-only test now uses a tiny in-file nopQuerier — its methods are never actually called for SourceOnly=true requests.

go.mod / go.sum

• github.com/polarsignals/frostdb — gone.
• github.com/polarsignals/iceberg-go — gone (was only used by the experimental Iceberg path inside the FrostDB branch).
• github.com/parquet-go/parquet-go — gone (was a transitive of frostdb; the AppendParquetValues paths in the vendored builders were stripped in *: Phase 2.B — vendor pqarrow/builder + arrowutils into pkg/query/internal #6355).

Test plan

• go build ./...
• go vet ./...
• go test -short ./... — all pass
• CI green
• Filed follow-up issue: testcontainers ClickHouse integration suite to restore the end-to-end coverage that was deleted here

🤖 Generated with Claude Code

[alwaysmeticulous]

✅ Meticulous spotted 0 visual differences across 288 screens tested: view results.

Meticulous evaluated ~4 hours of user flows against your PR.

_{Expected differences? Click here. Last updated for commit 6a422a6 *: Drop FrostDB-backed tests, rip frostdb out of go.mod. This comment will update as new commits are pushed.}