Development - VillageSQL Server for MySQL

This guide covers writing VDF implementations and running regression tests for VillageSQL extensions. It is the companion to Creating Extensions, which covers the end-to-end build steps.

VEF Protocol 3 is stable as of v0.0.4. Protocol 4 is under development and is available only via opt-in dev ABI headers (-DVSQL_USE_DEV_ABI=ON). Extensions built against the old Protocol 2 are rejected by the server and must be rebuilt.

If you are contributing to the VillageSQL server itself (not building an extension), see Build from Source, which covers the full server developer workflow including running tests with mysql-test-run.pl directly.

Setting Up Your Environment

To develop and test extensions, you need a built VillageSQL server. Follow the Clone and Build from Source guide to compile the server binaries. Once you have a build, use the villagesql CLI to manage a local dev server instance. Run all commands from the directory where VillageSQL was installed.

Starting a Local Dev Server

Initialize and start a server instance:

./villagesql init    # initialize database and seed bundled extensions
./villagesql start   # start the server (default port 3307)
./villagesql status  # check the server is running
./villagesql connect # open a mysql shell
./villagesql stop    # stop the server

To set a root password on init:

./villagesql init --password
./villagesql start

Pass --dir <path> before any command to manage multiple independent instances, or use --here to create a server directory in the current working directory:

./villagesql --here init
./villagesql --here start

Managing Extension Files

Before installing an extension via SQL, its .veb file must be present on the server. The CLI manages the server’s lib/veb/ directory:

./villagesql veb add /path/to/my_extension.veb  # copy a .veb to the server
./villagesql veb ls                              # list available .veb files
./villagesql veb rm my_extension                # remove a .veb file

.veb files placed in lib/veb/ before init are seeded automatically. After adding a file, install the extension via SQL:

INSTALL EXTENSION my_extension;

Writing Extension Functions

Extension functions are written in C++ and registered with VEF. Include a single header to access the full SDK:

#include <villagesql/vsql.h>

Typed Wrappers (Recommended)

Typed wrappers provide a type-safe interface for VDF parameters and results. The framework detects wrapper types in your function signature and adapts automatically — the make_func registration syntax is unchanged. Input wrappers: IntArg, RealArg, StringArg, CustomArg — each provides is_null() and value(). For parameterized custom types, CustomArgWith adds a params() accessor that returns the cached parsed params struct (see Parameterized Types). Result wrappers: IntResult, RealResult, StringResult, CustomResult — each provides set_null(), warning(msg), and error(msg). Scalar results also provide set(value). Buffer results provide buffer() and set_length(len). StringResult additionally provides set(std::string_view), which copies up to buffer().size() bytes from the view and sets the length in one call. For parameterized custom types, CustomResultWith adds a params() accessor. Span type: value() and buffer() on the byte-oriented wrappers return a vsql::Span<T> — a non-owning view over a contiguous run of T with data(), size(), empty(), begin()/end(), and operator[]. Under C++20 it is an alias for std::span<T>; under C++17 the SDK provides a minimal compatible implementation, so the same code compiles in either standard. It is available through <villagesql/vsql.h>. warning(msg) returns SQL NULL for the row and appends a SQL warning. In strict mode (STRICT_TRANS_TABLES), MySQL promotes it to a statement error on INSERT/UPDATE, so it behaves like error(msg) in strict contexts. Use it for recoverable bad input, such as an unparseable string in an encode function. Use error(msg) for corrupt stored data or any condition where continuing is unsafe. The message for both is truncated to fit the server’s internal error buffer if necessary. Scalar example — add two integers:

using namespace vsql;

void add_impl(IntArg a, IntArg b, IntResult out) {
  if (a.is_null() || b.is_null()) { out.set_null(); return; }
  out.set(a.value() + b.value());
}

// Registration is unchanged:
make_func<&add_impl>("add").returns(INT).param(INT).param(INT).build();

Binary example — transform a custom type buffer in place:

using namespace vsql;

void rot13_impl(CustomArg in, CustomResult out) {
  if (in.is_null()) { out.set_null(); return; }
  auto src = in.value();   // vsql::Span<const unsigned char>
  auto dst = out.buffer(); // vsql::Span<unsigned char>
  for (size_t i = 0; i < src.size(); i++) { dst[i] = transform(src[i]); }
  out.set_length(src.size());
}

For StringResult and CustomResult, write into buffer(), then call set_length() with the number of bytes written. buffer().size() is the maximum capacity. For VDFs that return a custom type (returns(CUSTOM(MYTYPE))), the server sizes the result buffer to the resolved return type’s persisted_length automatically — extension authors do not need to declare .buffer_size(...) on the function builder for this case. If prerun grows the buffer further, that larger size is preserved. This is what lets, for example, SVECTOR::from_string('[…1024 floats…]') encode a wide vector without the result wrapper running out of room. You can use different styles across functions in the same extension — each function’s style is determined by its own signature.

Aggregate VDFs

Aggregate VDFs accumulate state across rows within each GROUP BY group and return a single result per group, like SQL SUM or COUNT. Use make_aggregate_func<State, &result_fn>("name") to register one. The State type is the per-group accumulation buffer; prerun and postrun are auto-generated to allocate and delete it. The result function must have the signature void(const State&, ResultWrapper) where ResultWrapper is one of IntResult, RealResult, StringResult, CustomResult, or CustomResultWith. Call out.set(value) to return a value or out.set_null() to return SQL NULL. Both .clear<>() and .accumulate<>() are required. The builder enforces this at compile time (via build()), and the server validates it again at INSTALL EXTENSION time — clear resets state, accumulate folds rows, and the result function reads the final state.

#include <villagesql/vsql.h>
#include <optional>

using namespace vsql;

// State type: nullopt means no non-NULL rows seen yet.
using SumState = std::optional<long long>;

void my_clear(SumState &s) { s = std::nullopt; }
void my_acc(SumState &s, IntArg v) {
  if (!v.is_null()) s = s.value_or(0) + v.value();
}
void my_result(const SumState &s, IntResult out) {
  if (!s.has_value()) { out.set_null(); return; }
  out.set(s.value());
}

// Registration:
// make_aggregate_func<SumState, &my_result>("my_sum")
//     .returns(INT)
//     .param(INT)
//     .clear<&my_clear>()
//     .accumulate<&my_acc>()
//     .build()

How the builder methods work:

make_aggregate_func<State, &result_fn>() auto-generates prerun and postrun (value-initializes and deletes State).
.clear<&fn>() wraps void(State&) → vef_vdf_clear_func_t
.accumulate<&fn>() wraps void(State&, TypedArgs...) → vef_vdf_accumulate_func_t. TypedArgs are deduced from the function signature (IntArg, StringArg, etc.).
The ResultWrapper type (IntResult, RealResult, etc.) is deduced from the result function signature.

For a counter that never returns NULL, use a plain state type:

using CountState = long long;
void count_clear(CountState &s) { s = 0; }
void count_acc(CountState &s, IntArg v) { if (!v.is_null()) s++; }
void count_result(const CountState &s, IntResult out) { out.set(s); }

Per-Statement State (Prerun and Postrun)

Some VDFs need state that spans every row a single query touches — a call counter, a cached result, an open resource. Allocate it in a prerun hook, access it from the VDF body, and release it in a postrun hook. Both hooks run once per statement; the VDF body runs once per row. Register them with .prerun<&Hook>() and .postrun<&Hook>(). The required signatures are:

Hook	Required signature
Prerun	`void(vsql::PrerunArgs, vsql::PrerunResult)`
Postrun	`void(vsql::PostrunArgs)`

Raw ABI signatures are rejected at compile time. Use PrerunResult::set_user_data(void*) to stash state; use PostrunArgs::delete_state<T>() to release it. If prerun calls set_user_data(new T{}), postrun must call delete_state<T>() — the SDK does not auto-free. PrerunArgs::type_at(i) exposes the declared SQL type of each argument before any rows are read; the predicates is_int(), is_real(), is_str(), is_custom() on the returned PrerunArgType mirror the column types. Use this in prerun to validate argument types or call PrerunResult::request_buffer_size(n) to size the result buffer.

#include <villagesql/vsql.h>
using namespace vsql;

struct CallCounter { long long n = 0; };

void ba_call_index_prerun(PrerunArgs, PrerunResult out) {
  out.set_user_data(new CallCounter{});
}

void ba_call_index(CallCounter &state, IntResult out) {
  state.n++;
  out.set(state.n);
}

void ba_call_index_postrun(PostrunArgs args) {
  args.delete_state<CallCounter>();
}

// Registration:
// make_func<&ba_call_index>("ba_call_index")
//     .returns(INT).no_params()
//     .prerun<&ba_call_index_prerun>()
//     .postrun<&ba_call_index_postrun>()
//     .build()

Varargs VDFs

A varargs VDF accepts any number of arguments of any SQL type. Declare one with .varargs() on the func builder, which is mutually exclusive with .no_params() and .param(TYPE). The body receives a vsql::VarArgs argument instead of the usual fixed-arity wrappers.

Varargs registration requires VEF Protocol 3. Older servers reject the extension at install time.

The framework cannot validate argument count or types for varargs VDFs. Pair every varargs registration with a prerun hook that calls PrerunResult::error() on invalid input or PrerunResult::request_buffer_size(n) to size the result buffer. Iterate over arguments with range-for. Each AnyArg element requires a type check before reading its value:

Predicate	Accessor	Return type
`is_int()`	`as_int()`	`long long`
`is_real()`	`as_real()`	`double`
`is_str()`	`as_str()`	`std::string_view`
`is_custom()`	`as_custom()`	`vsql::Span<const unsigned char>`

Check is_null() before any accessor — all four are undefined on a null argument.

#include <villagesql/vsql.h>
#include <cstring>
using namespace vsql;

constexpr size_t kBytearrayLen = 4;

void ba_concat_all_prerun(PrerunArgs args, PrerunResult out) {
  if (args.size() == 0) {
    out.error("ba_concat_all requires at least one argument");
    return;
  }
  for (size_t i = 0; i < args.size(); i++) {
    auto t = args.type_at(i);
    if (!t.is_custom() && !t.is_str()) {
      out.error("ba_concat_all: argument " + std::to_string(i) +
                " must be BYTEARRAY");
      return;
    }
  }
  out.request_buffer_size(args.size() * kBytearrayLen);
}

void ba_concat_all(VarArgs args, StringResult out) {
  auto dst = out.buffer();
  size_t off = 0;
  for (auto a : args) {
    if (a.is_null() || !a.is_custom()) { out.set_null(); return; }
    auto bytes = a.as_custom();
    std::memcpy(dst.data() + off, bytes.data(), bytes.size());
    off += bytes.size();
  }
  out.set_length(off);
}

// Registration:
// make_func<&ba_concat_all>("ba_concat_all")
//     .returns(STRING).varargs()
//     .prerun<&ba_concat_all_prerun>()
//     .build()

VEF_GENERATE_REGISTRATION

VEF_GENERATE_REGISTRATION creates an internal _vef_do_register() helper that performs extension registration but does not define the extern "C" entry points. Use it when you need to customize vef_register behavior — for example, to patch descriptors after registration in a test build. For normal extensions, use VEF_GENERATE_ENTRY_POINTS instead.

VEF_GENERATE_REGISTRATION(
    make_extension()
        .func(make_func<&my_impl>("my_func").returns(INT).build()))

// Then define your own extern "C" vef_register/vef_unregister that call
// _vef_do_register() and optionally modify the result.

Type Operation Builders

Only needed if your extension defines a custom column type. If you’re writing functions only, skip ahead to Running Regression Tests. Custom types require three operations the engine calls internally: encode (string to binary), decode (binary to string), and compare. Hash is optional. Implement them against these C++ signatures (all available via <villagesql/vsql.h>):

Fixed-Length Types

// Encode: string -> binary. Write the encoded bytes via out.buffer() and
// out.set_length(n); call out.set_null() for SQL NULL, out.warning(msg) for
// recoverable bad input, or out.error(msg) to abort the statement. Returning
// without calling any of these surfaces a default warning.
using TypeEncodeFunc = void (*)(std::string_view from, vsql::CustomResult out);

// Decode: binary -> string. Report the outcome by calling
// out.set_length(n), out.set(sv), out.set_null(), out.warning(msg), or
// out.error(msg). If none is called the wrapper falls back to a default
// "failed to decode value" ERROR.
using TypeDecodeFunc = void (*)(vsql::CustomArg in, vsql::StringResult out);

// Compare: returns -1, 0, or 1 (used for ORDER BY and indexes).
using TypeCompareFunc = int (*)(vsql::CustomArg a, vsql::CustomArg b);

// Hash: returns hash code (used for hash joins).
using TypeHashFunc = size_t (*)(vsql::CustomArg in);

Register these operations using vsql::make_type<kTypeName>(). The type name is passed as a non-type template parameter (NTTP) — a static constexpr const char[] array. The builder auto-generates VDF names in the TYPE::method format (e.g., "MYTYPE::from_string") from this NTTP, so no manual string matching is required. Pass the built type object to .type() on the extension builder; separate .func() calls for type operations are not needed.

The type name must be a static constexpr const char[] variable — a string literal cannot be used as a non-type template parameter. Passing "MYTYPE" directly produces a compiler error like:

error: '"MYTYPE"' is not a valid template argument for type 'const char*'

Declare the name as a named array as shown below.

#include <villagesql/vsql.h>

using namespace vsql;

static constexpr const char kMyTypeName[] = "MYTYPE";

constexpr auto MYTYPE =
    vsql::make_type<kMyTypeName>()
        .persisted_length(8)
        .max_decode_buffer_length(64)
        .from_string<&my_encode>()   // auto: "MYTYPE::from_string"
        .to_string<&my_decode>()     // auto: "MYTYPE::to_string"
        .compare<&my_compare>()      // auto: "MYTYPE::compare"
        .hash<&my_hash>()            // optional, auto: "MYTYPE::hash"
        .intrinsic_default_str("0")  // string-literal intrinsic default
        .build();

VEF_GENERATE_ENTRY_POINTS(
    make_extension()
        .type(MYTYPE))

build() fails at compile time if from_string, to_string, or compare is missing. Each template method checks the function pointer signature via static_assert.

Intrinsic Default

When a NOT NULL custom-type column receives NULL under IGNORE mode (e.g., INSERT IGNORE or UPDATE IGNORE), the server calls the intrinsic default to produce a fallback value rather than raising an error. The intrinsic default provides a string representation; the server converts it to binary using the type’s from_string function.

If you omit both .intrinsic_default_str() and .intrinsic_default_vdf(), the server calls from_string("") as a fallback. This happens when the type is first used (at table creation), not at INSTALL EXTENSION. If your encode function rejects empty string — or encodes it to the wrong number of bytes — type initialization fails with an error visible in the SQL client:

Type 'MYTYPE' failed to initialize: from_string VDF encoded intrinsic
default input '' to N bytes, expected persisted_length=M

For fixed-length types, the default string must encode to exactly persisted_length bytes. Set an explicit default for any type where empty string is not a valid input.

String literal: .intrinsic_default_str() For a constant default, pass the string directly on the type builder (as shown in the fixed-length example above with .intrinsic_default_str("0")). VDF-based: .intrinsic_default_vdf() + make_intrinsic_default When the default value depends on type parameters, implement a function against one of these signatures (available via <villagesql/vsql.h>):

Breaking change: IntrinsicDefaultFunc and IntrinsicDefaultWithParamsFunc return std::string instead of const char*. Update any existing intrinsic default implementations to return std::string directly.

// Fixed (no type parameters):
using IntrinsicDefaultFunc = std::string (*)(char *error_msg);

// Parameterized (receives cached parsed params):
template <typename P>
using IntrinsicDefaultWithParamsFunc = std::string (*)(const P &,
                                                       char *error_msg);

Return a std::string representation of the default value. On error, write a message to error_msg and return any value (the SDK checks error_msg[0] != '\0' to detect errors). Register with make_intrinsic_default<&fn>("vdf_name") (one argument: the VDF name) and reference that name on the type builder with .intrinsic_default_vdf(). The parameterized types example below shows the full registration pattern.

std::string mytype_default(const MyTypeParams &p, char * /*error_msg*/) {
  return /* build string representation based on p */;
}

Parameterized Types

Variable-length types need the column’s declared parameters at encode, decode, compare, and hash time to determine allocation sizes and layout. Define a params struct with a parse function and an inverse to_strings function, register both on the type builder with .params<P, &ParseFunc, &ToStringsFunc>(), and use const P& as the first argument of your type operation functions. The SDK caches the parse result per unique parameter combination, so the parse function runs at most once per type instantiation. The to_strings function is the inverse of parse: it writes a typed P back into the canonical key/value string form so the server can publish inferred params in the same shape parse consumes.

struct MyTypeParams {
  int64_t dimension;
  static MyTypeParams parse(const std::map<std::string, std::string> &p) {
    return {.dimension = stoll(p.at("dimension"))};
  }
  static void to_strings(const MyTypeParams &p,
                         std::map<std::string, std::string> &out) {
    out["dimension"] = std::to_string(p.dimension);
  }
};

void mytype_encode(vsql::MaybeParams<MyTypeParams> &params,
                   std::string_view from, vsql::CustomResult out) {
  const MyTypeParams &p = params.value();  // is_known() is always true at runtime
  size_t bytes = (size_t)p.dimension * 4;
  auto buf = out.buffer();
  if (buf.size() < bytes) { out.error("MYTYPE: buffer too small"); return; }
  // ... parse from, write to buf ...
  out.set_length(bytes);
}

void mytype_decode(vsql::CustomArgWith<MyTypeParams> in,
                   vsql::StringResult out) {
  const MyTypeParams &p = in.params();
  // ... read p.dimension floats from in.value(), write to out.buffer() ...
  out.set_length(bytes_written);
}

int mytype_compare(vsql::CustomArgWith<MyTypeParams> a,
                   vsql::CustomArgWith<MyTypeParams> b) {
  // Returns -1, 0, or 1.
}

size_t mytype_hash(vsql::CustomArgWith<MyTypeParams> in) {
  // Returns hash code.
}

// Converts MYTYPE(N) integer syntax to a parameter map.
// Signature: IntToTypeParamsFunc from <villagesql/vsql.h>.
bool mytype_int_to_params_fn(int64_t value,
                             std::map<std::string, std::string> &params,
                             char *error_msg) {
  if (value <= 0) {
    snprintf(error_msg, VEF_MAX_ERROR_LEN,
             "MYTYPE: dimension must be a positive integer");
    return true;
  }
  params["dimension"] = std::to_string(value);
  return false;  // success
}

// Validates parameters and computes storage sizes.
// Signature: ResolveTypeParamsFunc from <villagesql/vsql.h>.
bool mytype_resolve_params_fn(const std::map<std::string, std::string> &params,
                              vsql::ResolvedTypeParams *result,
                              char *error_msg) {
  int64_t dim = std::stoll(params.at("dimension"));
  result->persisted_length = dim * 4;
  result->max_decode_buffer_length = 64;
  return false;  // success
}

Register .params<>() on the type builder. Use .int_to_params<&mytype_int_to_params_fn>() to handle MYTYPE(N) integer syntax and .resolve_params<&mytype_resolve_params_fn>() to validate parameters and compute storage sizes. Call .max_persisted_length(N) with an upper bound on the persisted byte size across all valid parameterizations; the server uses this only on the type parameter inference path, where it has not yet inferred the params and so cannot consult resolve_params to size the encode buffer. For a VDF-based intrinsic default, use .intrinsic_default_vdf() with the VDF name and register the VDF separately via make_intrinsic_default<&mytype_default>().

static constexpr const char kMyTypeName[] = "MYTYPE";

// Maximum valid dimension for MYTYPE.
constexpr int64_t kMyTypeMaxDimension = 1024;  // your max valid dimension
// Upper bound on MYTYPE's persisted byte size across all valid params.
constexpr int64_t kMyTypeMaxPersistedLength = kMyTypeMaxDimension * 4;

constexpr auto MYTYPE =
    vsql::make_type<kMyTypeName>()
        .persisted_length(-1)
        .max_decode_buffer_length(16)
        .max_persisted_length(kMyTypeMaxPersistedLength)
        .params<MyTypeParams, &MyTypeParams::parse, &MyTypeParams::to_strings>()
        .int_to_params<&mytype_int_to_params_fn>()
        .resolve_params<&mytype_resolve_params_fn>()
        .from_string<&mytype_encode>()
        .to_string<&mytype_decode>()
        .compare<&mytype_compare>()
        .intrinsic_default_vdf("mytype_intrinsic_default")
        .build();

using namespace vsql;

VEF_GENERATE_ENTRY_POINTS(
    make_extension()
        .type(MYTYPE)
        .func(make_intrinsic_default<&mytype_default>(
            "mytype_intrinsic_default")))

The parameterized variants — TypeEncodeWithParamsFunc, TypeDecodeWithParamsFunc, TypeCompareWithParamsFunc, and TypeHashWithParamsFunc — together with ParamsToStringsFunc (void fn(const P&, std::map<std::string,std::string>&)) are available via <villagesql/vsql.h>. The vsql::make_type template methods detect the params argument and route through the params cache automatically. Encode functions take vsql::MaybeParams & as the first argument; is_known() is always true at runtime, and value() returns const P&. Decode, compare, and hash variants take vsql::CustomArgWith, whose params() accessor returns const P&.

Custom Types in Stored Procedures

Custom extension types can be used as stored procedure parameter types and in DECLARE variable declarations. The server resolves the custom type at routine execution time using the installed extension’s type metadata.

DELIMITER //
CREATE PROCEDURE insert_complex(IN val COMPLEX)
BEGIN
  DECLARE tmp COMPLEX;
  SET tmp = val;
  INSERT INTO t1 VALUES (tmp);
END //
DELIMITER ;

Extension System Variables

Extension system variables are a preview capability — see Preview Capabilities for the full API reference, factory functions, SQL access, and a complete example.

Extension Status Variables

Extension status variables are a preview capability — see Preview Capabilities for the full API reference, factory functions, SQL access, and a complete example.

Keyring Access

Keyring access is a preview capability — see Preview Capabilities for the full API reference, result codes, and a complete example.

Column Storage

Column storage is a preview capability — see Preview Capabilities for the full API reference and a complete example.

Inspecting Extension Registration Metadata

INFORMATION_SCHEMA.EXTENSION_REGISTRATION exposes the in-memory VEF registration struct for each loaded extension as a JSON document. Use it to verify that the server parsed your extension’s functions, types, and system variables correctly after INSTALL EXTENSION.

SELECT EXTENSION_NAME, NEGOTIATED_PROTOCOL, REGISTRATION_JSON
FROM INFORMATION_SCHEMA.EXTENSION_REGISTRATION
WHERE EXTENSION_NAME = 'my_ext';

Column	Type	Description
`EXTENSION_NAME`	`VARCHAR(64)`	Name of the installed extension.
`NEGOTIATED_PROTOCOL`	`BIGINT UNSIGNED`	VEF protocol version negotiated between the extension and the server.
`REGISTRATION_JSON`	`TEXT`	JSON serialization of the `vef_registration_t` struct, including `funcs` and `types` arrays.

Running Regression Tests

Run extension regression tests using the MySQL Test Runner from your VillageSQL build directory.

Running the Full Suite

To run all tests for your extension:

cd $BUILD_HOME
./mysql-test/mysql-test-run.pl --suite=/path/to/your/extension/test --parallel=auto

Running Individual Tests

To run a single test case, specify the suite path and test name:

cd $BUILD_HOME
./mysql-test/mysql-test-run.pl --suite=/path/to/your/extension/test my_test_name

Creating New Tests

When adding new features or fixing bugs, you should add corresponding regression tests.

Test Location

Extension tests live in the extension’s own repository under a test/ directory — not in the VillageSQL server’s mysql-test/suite/ tree.

Test files end with .test and go in test/t/.
Expected result files end with .result and go in test/r/.

For example, for an extension named my_extension:

test/t/my_new_test.test
test/r/my_new_test.result

Test File Conventions

A typical extension test installs the extension, runs SQL, and uninstalls:

# Description of the test

INSTALL EXTENSION my_extension;

# ... Your Test Code Here ...
CREATE TABLE t1 (val MYTYPE);
INSERT INTO t1 VALUES ('some_value');
SELECT * FROM t1;
DROP TABLE t1;

UNINSTALL EXTENSION my_extension;

When your test output includes paths from the test runner’s temp directory, add this directive inside your .test file to normalize them — without it, recorded results contain absolute paths that break on other machines:

--replace_result $MYSQLTEST_VARDIR MYSQLTEST_VARDIR

Steps to Add a Test

Create the .test file in your extension’s test/t/ directory.
Create an empty .result file in your extension’s test/r/ directory.

Run the test with --record to generate the expected output:

cd $BUILD_HOME
./mysql-test/mysql-test-run.pl --suite=/path/to/your/extension/test --record my_new_test

Verify the output in the generated .result file to ensure it matches your expectations.

Debugging Tests

If a test fails, the test framework provides detailed logs.

Test output: Check mysql-test/var/log/mysqltest.log (combined) or mysql-test/var/log/<test_name>/ (per-test directory).
Server error log: Check mysql-test/var/log/mysqld.1.err. VillageSQL-specific log messages (emitted via LogVSQL()) only appear when the server runs with --log-error-verbosity=3.
Diff: The framework outputs a diff between the actual output and the expected .result file.

To run a test with extra debug information:

cd $BUILD_HOME
./mysql-test/mysql-test-run.pl --verbose --suite=/path/to/your/extension/test my_new_test

# To surface LogVSQL() messages in the error log:
./mysql-test/mysql-test-run.pl --mysqld=--log-error-verbosity=3 \
    --suite=/path/to/your/extension/test my_new_test

​Setting Up Your Environment

​Starting a Local Dev Server

​Managing Extension Files

​Writing Extension Functions

​Typed Wrappers (Recommended)

​Aggregate VDFs

​Per-Statement State (Prerun and Postrun)

​Varargs VDFs

​VEF_GENERATE_REGISTRATION

​Type Operation Builders

​Fixed-Length Types

​Intrinsic Default

​Parameterized Types

​Custom Types in Stored Procedures

​Extension System Variables

​Extension Status Variables

​Keyring Access

​Column Storage

​Inspecting Extension Registration Metadata

​Running Regression Tests

​Running the Full Suite

​Running Individual Tests

​Creating New Tests

​Test Location

​Test File Conventions

​Steps to Add a Test

​Debugging Tests

​See Also

Setting Up Your Environment

Starting a Local Dev Server

Managing Extension Files

Writing Extension Functions

Typed Wrappers (Recommended)

Aggregate VDFs

Per-Statement State (Prerun and Postrun)

Varargs VDFs

VEF_GENERATE_REGISTRATION

Type Operation Builders

Fixed-Length Types

Intrinsic Default

Parameterized Types

Custom Types in Stored Procedures

Extension System Variables

Extension Status Variables

Keyring Access

Column Storage

Inspecting Extension Registration Metadata

Running Regression Tests

Running the Full Suite

Running Individual Tests

Creating New Tests

Test Location

Test File Conventions

Steps to Add a Test

Debugging Tests

See Also