From 50bca2343157b232232c906ffe355f159a548356 Mon Sep 17 00:00:00 2001
From: Josh Ventura <Josh.Ventura@ClickHouse.com>
Date: Wed, 17 Jun 2026 17:48:17 -0700
Subject: [PATCH] refactor(exporter): remove dead MetricFixedString interface
 method + FixedStringCol class
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`MetricFixedString` was added in Feb 2026 (commit 9f89f4) when err_sqlstate
was the only column in events_raw of type FixedString(5). It had exactly
one caller, exactly one width, and was always going to.

PR #99 (merged 2026-06-10) changed err_sqlstate from FixedString(5) to
LowCardinality(String) and updated the call site from
`exporter->MetricFixedString(5, "err_sqlstate")` to
`exporter->TagString("err_sqlstate")`. The interface method became
unreferenced.

PR #104 (merged 2026-06-04 — before #99) had to reproduce
MetricFixedString in clickhouse-c by hand-rolling a `FixedStringCol`
class, since clickhouse-c has no built-in FixedString column type
unlike clickhouse-cpp. That work was correct when authored — the
column was still live — but became orphaned a week later when #99
landed. Nobody noticed.

Deletes the now-dead virtual + both impls. The CH-native side loses
the 27-line FixedStringCol class entirely; the OTel side loses a
3-line forward to MakeSvCol; the interface loses one virtual
declaration. Stats_exporter.cc already doesn't reference it.

No behavior change — this was unreachable code. -35 LOC.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 src/export/clickhouse_exporter.cc | 31 -------------------------------
 src/export/exporter_interface.h   |  1 -
 src/export/otel_exporter.cc       |  4 ----
 3 files changed, 36 deletions(-)

diff --git a/src/export/clickhouse_exporter.cc b/src/export/clickhouse_exporter.cc
index cbdb04b..23fe1c6 100644
--- a/src/export/clickhouse_exporter.cc
+++ b/src/export/clickhouse_exporter.cc
@@ -176,9 +176,6 @@ class ClickHouseExporter : public StatsExporter {
   shared_ptr<Column<uint64_t>> MetricUInt64(string_view name) final {
     return MakeCol<FixedCol<uint64_t>>(name, "UInt64");
   }
-  shared_ptr<Column<string_view>> MetricFixedString(int len, string_view name) final {
-    return MakeCol<FixedStringCol>(name, len);
-  }
 
   shared_ptr<Column<int16_t>> RecordInt16(string_view name) final {
     return MakeCol<FixedCol<int16_t>>(name, "Int16");
@@ -264,34 +261,6 @@ class ClickHouseExporter : public StatsExporter {
     std::vector<uint64_t> offsets_;
   };
 
-  class FixedStringCol : public Column<string_view> {
-   public:
-    FixedStringCol(ClickHouseExporter* exp, string_view name, int n)
-        : exp_(exp),
-          name_(name),
-          width_(static_cast<size_t>(n)),
-          type_name_("FixedString(" + std::to_string(n) + ")") {}
-    void Append(const string_view& s) final {
-      const size_t start = data_.size();
-      data_.resize(start + width_, '\0');
-      std::memcpy(data_.data() + start, s.data(), std::min(s.size(), width_));
-      ++rows_;
-    }
-    void Crunch() final { exp_->AppendFixed(name_, type_name_.c_str(), data_.data(), rows_); }
-    void Clear() final {
-      data_.clear();
-      rows_ = 0;
-    }
-
-   private:
-    ClickHouseExporter* const exp_;
-    const std::string name_;
-    const size_t width_;
-    const std::string type_name_;
-    std::vector<char> data_;
-    size_t rows_ = 0;
-  };
-
   template <typename ColT, typename... Args>
   shared_ptr<ColT> MakeCol(string_view name, Args&&... args) {
     if (auto it = col_index_.find(name); it != col_index_.end()) {
diff --git a/src/export/exporter_interface.h b/src/export/exporter_interface.h
index afbc8c9..249e82e 100644
--- a/src/export/exporter_interface.h
+++ b/src/export/exporter_interface.h
@@ -37,7 +37,6 @@ class StatsExporter {
   virtual shared_ptr<Column<int64_t>> MetricInt64(string_view name) = 0;
   virtual shared_ptr<Column<uint8_t>> MetricUInt8(string_view name) = 0;
   virtual shared_ptr<Column<uint64_t>> MetricUInt64(string_view name) = 0;
-  virtual shared_ptr<Column<string_view>> MetricFixedString(int len, string_view name) = 0;
 
   // Records: Data columns you wouldn't want to filter by.
   virtual shared_ptr<Column<int16_t>> RecordInt16(string_view name) = 0;
diff --git a/src/export/otel_exporter.cc b/src/export/otel_exporter.cc
index ad9228e..3c7f8d6 100644
--- a/src/export/otel_exporter.cc
+++ b/src/export/otel_exporter.cc
@@ -170,10 +170,6 @@ class OTelExporter : public StatsExporter {
   shared_ptr<Column<uint64_t>> MetricUInt64(string_view name) final {
     return MakeIntCol<uint64_t>(name);
   }
-  shared_ptr<Column<string_view>> MetricFixedString(int /*len*/, string_view name) final {
-    return MakeSvCol(name);
-  }
-
   shared_ptr<Column<int16_t>> RecordInt16(string_view name) final {
     return MakeIntCol<int16_t>(name);
   }