vsql-stat-core

Shared capture pipeline for the vsql-stat family of VillageSQL query-telemetry extensions. This is source-only — the sinks compile these files directly. Each sink extension (vsql-stat-ch, vsql-stat-http, vsql-stat-slowlog) vendors these files under its own core/ directory (via git subtree) and compiles them into its .veb. The only build here is the standalone unit test (below).

What's here

Sources live at the repo root (so a sink's git subtree add --prefix=core places them at core/* in the consumer):

File	Role
event_row.h	the backend-agnostic captured statement row
event_queue.{h,cc}	bounded MPSC queue (drop-newest overflow)
sink.h	the Sink interface each extension implements
capture_pipeline.{h,cc}	POSTEXECUTE-hook capture + background-worker flush
test/event_queue_test.cc	standalone unit test for the queue

A sink extension provides a Sink implementation and its transport/config; the core owns capture, buffering, and the flush worker, so that logic is written once and shared.

Testing

The queue logic (bounded capacity, drop-newest overflow, drain, counters) has a standalone unit test — pure C++, no VillageSQL SDK, no server, no external service:

cmake -S . -B build && cmake --build build && ctest --test-dir build

The capture pipeline (capture_pipeline) binds to SDK preview capabilities and is exercised end to end via each sink's mtr suite rather than here.

How a sink consumes it

Vendored into the extension repo under core/ with git subtree:

# first time, in the extension repo:
git subtree add --prefix=core <vsql-stat-core-remote> main --squash

# to pull a later core change:
git subtree pull --prefix=core <vsql-stat-core-remote> main --squash

The extension's CMakeLists.txt then lists core/event_queue.cc and core/capture_pipeline.cc in its add_library and adds the repo root to the include path so #include "core/..." resolves.

Compatibility

The core binds to the VillageSQL SDK preview capabilities (statement_event, thread_worker) and uses fixed-width ABI types (int64_t for sysvar/status bindings). It tracks the SDK the sink extensions build against.