Add sqlcommenter feature for traceparent SQL comments

Cargo.toml

@@ -67,6 +67,14 @@ derive = ["sqlx-macros/derive"]
 macros = ["derive", "sqlx-macros/macros", "sqlx-core/offline", "sqlx-mysql?/offline", "sqlx-postgres?/offline", "sqlx-sqlite?/offline"]
 migrate = ["sqlx-core/migrate", "sqlx-macros?/migrate", "sqlx-mysql?/migrate", "sqlx-postgres?/migrate", "sqlx-sqlite?/migrate"]
 
+# Append sqlcommenter trailing comments to outgoing queries on backends that
+# support it (PostgreSQL, MySQL — SQLite has no managed observability
+# consumer). Pulls trace context from OTel's globally configured propagator
+# (typically W3C TraceContext via `tracing-opentelemetry`). When a comment
+# is appended, the backend executor routes through the non-cached prepare
+# path so the statement cache isn't polluted with one-shot entries.
+sqlcommenter = ["sqlx-core/sqlcommenter", "sqlx-mysql?/sqlcommenter", "sqlx-postgres?/sqlcommenter"]
+
 # Enable parsing of `sqlx.toml` for configuring macros and migrations.
 sqlx-toml = ["sqlx-core/sqlx-toml", "sqlx-macros?/sqlx-toml", "sqlx-sqlite?/sqlx-toml"]
 

sqlx-core/Cargo.toml

@@ -45,6 +45,19 @@ sqlx-toml = ["serde", "toml/parse"]
 
 _unstable-doc = ["sqlx-toml"]
 
+# Append a sqlcommenter-style trailing comment to each query sent to the
+# database, sourcing trace context from OTel's globally configured
+# `TextMapPropagator` (typically W3C TraceContext, yielding `traceparent` and
+# `tracestate`). Lets server-side observability tools (Cloud SQL Insights,
+# AlloyDB Insights, etc.) correlate query stats with upstream traces.
+# Requires the user's app to have a propagator registered (otherwise no
+# comment is emitted).
+#
+# Note: when a comment is appended, the backend executor routes through the
+# non-cached prepare path so we don't fill the statement cache with one-shot
+# entries. Same wire round-trips, no cache pollution.
+sqlcommenter = ["dep:opentelemetry", "dep:tracing-opentelemetry"]
+
 [dependencies]
 # Runtimes
 async-global-executor = { workspace = true, optional = true }
@@ -96,6 +109,8 @@ sha2 = { version = "0.10.0", default-features = false, optional = true }
 #sqlformat = "0.2.0"
 tokio-stream = { version = "0.1.8", features = ["fs"], optional = true }
 tracing = { version = "0.1.37", features = ["log"] }
+opentelemetry = { version = "0.30", default-features = false, features = ["trace"], optional = true }
+tracing-opentelemetry = { version = "0.31", default-features = false, optional = true }
 smallvec = "1.13.1"
 url = { version = "2.2.2" }
 bstr = { version = "1.0.1", default-features = false, features = ["std"], optional = true }

sqlx-core/src/lib.rs

@@ -73,6 +73,7 @@ pub mod query_as;
 pub mod query_builder;
 pub mod query_scalar;
 pub mod sql_str;
+pub mod sqlcommenter;
 
 pub mod raw_sql;
 pub mod row;