Add focused Prometheus protocol tests for user-facing native lowering errors: unsupported-but-parseable functions and invalid date-function arity. These are semantic guardrails for clear errors, not broad coverage padding.

Implement native SQL lowering for PromQL count_values(label, vector) using the existing TimeSeries group/tag representation. The lowering formats sample values as Prometheus label strings, overwrites the destination label before aggregation, handles by/without grouping, and packs per-step counts back onto the vector grid.

Also adds focused differential coverage for value formatting, destination-label overwrite, grouping variants, sparse subquery results, and empty inputs, plus compliance cases for count_values variants.

Validation: git diff --check; Python py_compile for updated PromQL tests; Dockerized Build (amd_debug) passed; focused test_aggregation_operators passed; test_promql_compliance passed.

Avoid fork-local wording in the PromQL review base. These are ClickHouse PromQL regression cases and evidence requirements, not fork-specific artifacts.

Avoid fork-local wording in the PromQL review base. These are ClickHouse PromQL regression cases and evidence requirements, not fork-specific artifacts.

Remove the standalone native histogram discovery Markdown note from the PromQL split branches.

Remove the standalone native histogram discovery Markdown note from the PromQL split branches.

Remove downstream promshim-specific evidence and non-goal language from the native PromQL lowering README so the note stays focused on ClickHouse review guidance.

Remove downstream promshim-specific evidence and non-goal language from the native PromQL lowering README so the note stays focused on ClickHouse review guidance.

Rewrite the native PromQL lowering notes around external SQL-transpiler measurements. Document measured and mixed SQL patterns with target PromQL shapes, pseudocode, and the ClickHouse-side validation expected for in-tree changes.

Rewrite the native PromQL lowering notes around external SQL-transpiler measurements. Document measured and mixed SQL patterns with target PromQL shapes, pseudocode, and the ClickHouse-side validation expected for in-tree changes.

Replace external corpus row names with concrete PromQL expressions and query-range context in the native PromQL lowering notes.

Replace external corpus row names with concrete PromQL expressions and query-range context in the native PromQL lowering notes.

Deduplicate expanded compliance cases by query text before checking the
`should_fail` expectation. A query listed once as expected success and once as
expected failure is now reported as conflicting metadata instead of slipping
through as two separate cases.

…plit/promql-count-values

Mirror the upstream PromQL compliance corpus for label transformation invalid
label-name cases. These cases should remain should-fail entries so ClickHouse
acceptance of invalid destination labels stays visible as a rejection mismatch
rather than being counted as expected coverage.

`count_values` creates an output label from its string argument. Keep that
argument constrained to PromQL label-name syntax instead of accepting every
non-empty UTF-8 string, so invalid names such as `~invalid` are rejected before
rendering a label key that selectors cannot address.

…on-base

Do not stop selector validation after finding the first matcher that cannot match an empty label value. Later regex matchers still need syntax validation so equivalent selector reorderings cannot change parse validity.

Add parser regressions for invalid regex matchers after an implicit metric-name matcher and after explicit non-empty matchers.

…plit/promql-count-values

Use Prometheus UTF-8 label-name validation for the generated value label, so current Prometheus-valid names such as ~value are accepted while empty labels still fail.

Add focused and compliance coverage for generated-label insertion before grouping, by/without behavior, label overwrite, FormatFloat edge cases including -0, empty inputs, and scalar-grid range evaluation.

Validation:
- ninja -C build_debug clickhouse
- test_evaluation.py::test_aggregation_operators
- test_compliance.py::test_promql_compliance

Ignore string literals and selector matchers when routing compliance failures by query shape. This keeps report categories from treating label values or exponent signs as binary operators, and recognizes bare '<' and '>' comparisons.

Use the existing eps parameter when checking live Prometheus HTTP results against expected JSON, and compare ClickHouse HTTP output against the live Prometheus result. This keeps numeric drift bounded to eps while preserving exact shape, label, and timestamp checks.

Prometheus excludes __name__ from without-grouping keys even when count_values writes its generated sample-value label to __name__. Cover that behavior explicitly so the ClickHouse SQL lowering keeps collapsing buckets by the remaining labels instead of preserving the generated metric name as a grouping key.

…-base

…values

Keep the PromQL parser, modifier, and selector fixes from the local matrix pass, but move the high-value regression coverage into the existing protocol and compliance suites instead of adding the standalone matrix harness to the PR branch.\n\nThis keeps fixed-time range evaluation covered through the existing evaluation tests and records the parser, matcher, timestamp-modifier, and sparse range cases in the shared compliance corpus.

Build (arm_tidy) flagged the vector-grid finalization predicate because one call cloned an AST pointer while another argument moved the same pointer. C++ argument evaluation order can make that a use-after-move.\n\nCreate separate AST nodes for the null and stale-marker checks so the generated predicate stays the same without relying on argument evaluation order.

Parse `@ start()` and `@ end()` as timestamp modifier variants instead of
rewriting the raw query text before parsing. This keeps label values and
regular expressions untouched while resolving symbolic bounds in the query
range planner.

Propagate symbolic `@` modifiers through the PromQL tree and SQL lowering so
instant selectors and range-vector functions bind to the query start or end
consistently with Prometheus.

The selector-matcher validation branch should not also introduce symbolic
`@ start()` and `@ end()` modifier parsing. Remove that parser/evaluation
feature from the base branch so the behavior can be reviewed independently.

Move the symbolic timestamp-modifier compliance cases out with the feature.
Keep the offset-only case here because it exercises existing modifier behavior.

Symbolic `@ start()` and `@ end()` modifiers need parser-level handling so
selectors, string literals, and regular expressions are not rewritten as raw
text. Remove the temporary text-substitution path from the base branch; the
symbolic modifier implementation belongs with the dedicated parser change.

…-base

…-base