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Mark HTTP request functions VOLATILE to prevent double execution on constant arguments #37

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Merged
rustyconover merged 1 commit into from
Sep 8, 2026
Merged

Mark HTTP request functions VOLATILE to prevent double execution on constant arguments #37

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36 changes: 28 additions & 8 deletions src/http_client_extension.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -409,31 +409,51 @@ namespace duckdb
});
}

// Every function here performs a network request — a side effect. Such
// functions MUST be VOLATILE, otherwise DuckDB's optimizer treats them as
// pure and may evaluate a call with all-constant arguments at plan time
// (constant folding) in addition to execution time. Concretely, nesting a
// call inside a larger constant expression — the common idiom
// SELECT http_post('http://…', …)->>'access_token'
// — sends the request TWICE on one query. The query result is still a
// single correct row, so the duplicate is only visible in the server's
// logs; for non-idempotent endpoints (OAuth code exchange, webhooks,
// POSTs that create rows) it is a correctness bug. Marking the functions
// volatile (same class as random()/nextval()) pins one request per
// logical call. Verified: nested constant-arg http_post sends 2 without
// volatile, exactly 1 with it; column/bind arguments already sent once
// and are unaffected.
static ScalarFunction MakeVolatile(ScalarFunction fn)
{
fn.SetVolatile();
return fn;
}

static void LoadInternal(ExtensionLoader &loader)
{
ScalarFunctionSet http_head("http_head");
http_head.AddFunction(ScalarFunction({LogicalType::VARCHAR}, LogicalType::JSON(), HTTPHeadRequestFunction));
http_head.AddFunction(MakeVolatile(ScalarFunction({LogicalType::VARCHAR}, LogicalType::JSON(), HTTPHeadRequestFunction)));
loader.RegisterFunction(http_head);

ScalarFunctionSet http_get("http_get");
http_get.AddFunction(ScalarFunction({LogicalType::VARCHAR}, LogicalType::JSON(), HTTPGetRequestFunction));
http_get.AddFunction(ScalarFunction(
http_get.AddFunction(MakeVolatile(ScalarFunction({LogicalType::VARCHAR}, LogicalType::JSON(), HTTPGetRequestFunction)));
http_get.AddFunction(MakeVolatile(ScalarFunction(
{LogicalType::VARCHAR, LogicalType::MAP(LogicalType::VARCHAR, LogicalType::VARCHAR),
LogicalType::MAP(LogicalType::VARCHAR, LogicalType::VARCHAR)},
LogicalType::JSON(), HTTPGetExRequestFunction));
LogicalType::JSON(), HTTPGetExRequestFunction)));
loader.RegisterFunction(http_get);

ScalarFunctionSet http_post("http_post");
http_post.AddFunction(ScalarFunction(
http_post.AddFunction(MakeVolatile(ScalarFunction(
{LogicalType::VARCHAR, LogicalType::MAP(LogicalType::VARCHAR, LogicalType::VARCHAR), LogicalType::JSON()},
LogicalType::JSON(), HTTPPostRequestFunction));
LogicalType::JSON(), HTTPPostRequestFunction)));
loader.RegisterFunction(http_post);

ScalarFunctionSet http_post_form("http_post_form");
http_post_form.AddFunction(ScalarFunction(
http_post_form.AddFunction(MakeVolatile(ScalarFunction(
{LogicalType::VARCHAR, LogicalType::MAP(LogicalType::VARCHAR, LogicalType::VARCHAR),
LogicalType::MAP(LogicalType::VARCHAR, LogicalType::VARCHAR)},
LogicalType::JSON(), HTTPPostFormRequestFunction));
LogicalType::JSON(), HTTPPostFormRequestFunction)));
loader.RegisterFunction(http_post_form);

QueryFarmSendTelemetry(loader, "http_client", "2026072501");
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