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Use simdjson for json_parse #7658

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Use simdjson for json_parse #7658

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40 changes: 32 additions & 8 deletions velox/functions/prestosql/JsonFunctions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
* limitations under the License.
*/
#include "velox/expression/VectorFunction.h"
#include "velox/functions/prestosql/json/SIMDJsonWrapper.h"
#include "velox/functions/prestosql/types/JsonType.h"

namespace facebook::velox::functions {
Expand Down Expand Up @@ -70,19 +71,27 @@ class JsonParseFunction : public exec::VectorFunction {
const TypePtr& /* outputType */,
exec::EvalCtx& context,
VectorPtr& result) const override {
folly::call_once(initializeErrors_, [this] {
// Initilize errors here so that we get the proper exception context.
for (int i = 1; i < simdjson::NUM_ERROR_CODES; ++i) {
simdjson::simdjson_error e(static_cast<simdjson::error_code>(i));
errors_[i] = toVeloxException(std::make_exception_ptr(e));
}
});

VectorPtr localResult;

// Input can be constant or flat.
// TODO(arpitporwal2293) Replace folly::parseJson with a lightweight
// validation of JSON syntax that doesn't allocate memory or copy data.
assert(args.size() > 0);
const auto& arg = args[0];
static_assert(simdjson::SIMDJSON_PADDING <= AlignedBuffer::kPaddedSize);
if (arg->isConstantEncoding()) {
auto value = arg->as<ConstantVector<StringView>>()->valueAt(0);
try {
folly::parseJson(value);
} catch (const std::exception& e) {
context.setErrors(rows, std::current_exception());
auto parsed = parser_.parse(value.data(), value.size(), false);
if (parsed.error() != simdjson::SUCCESS) {
context.setErrors(rows, errors_[parsed.error()]);
return;
}
localResult = std::make_shared<ConstantVector<StringView>>(
Expand All @@ -93,8 +102,13 @@ class JsonParseFunction : public exec::VectorFunction {
auto stringBuffers = flatInput->stringBuffers();
VELOX_CHECK_LE(rows.end(), flatInput->size());

context.applyToSelectedNoThrow(
rows, [&](auto row) { folly::parseJson(flatInput->valueAt(row)); });
rows.applyToSelected([&](auto row) {
auto value = flatInput->valueAt(row);
auto parsed = parser_.parse(value.data(), value.size(), false);
if (parsed.error() != simdjson::SUCCESS) {
context.setVeloxExceptionError(row, errors_[parsed.error()]);
}
});
localResult = std::make_shared<FlatVector<StringView>>(
context.pool(),
JSON(),
Expand All @@ -114,6 +128,11 @@ class JsonParseFunction : public exec::VectorFunction {
.argumentType("varchar")
.build()};
}

private:
mutable folly::once_flag initializeErrors_;
mutable std::exception_ptr errors_[simdjson::NUM_ERROR_CODES];
mutable simdjson::dom::parser parser_;
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@PHILO-HE PHILO-HE Nov 22, 2023 •
edited
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Hi @Yuhta, I note simdjson's ondemand parser has better performance, but has some limitations, e.g., it will not validate the full input. Is dom parser intentionally used here? Ref. link.

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Yes I tried ondemand parser first and find it is not able to invalidate some malformed JSON.

};

} // namespace
Expand All @@ -123,8 +142,13 @@ VELOX_DECLARE_VECTOR_FUNCTION(
JsonFormatFunction::signatures(),
std::make_unique<JsonFormatFunction>());

VELOX_DECLARE_VECTOR_FUNCTION(
VELOX_DECLARE_STATEFUL_VECTOR_FUNCTION(
udf_json_parse,
JsonParseFunction::signatures(),
std::make_unique<JsonParseFunction>());
[](const std::string& /*name*/,
const std::vector<exec::VectorFunctionArg>&,
const velox::core::QueryConfig&) {
return std::make_shared<JsonParseFunction>();
});

} // namespace facebook::velox::functions
16 changes: 12 additions & 4 deletions velox/functions/prestosql/tests/JsonFunctionsTest.cpp
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Expand Up @@ -197,10 +197,11 @@ TEST_F(JsonFunctionsTest, jsonParse) {
EXPECT_EQ(jsonParse(R"({"k1":"v1"})"), R"({"k1":"v1"})");
EXPECT_EQ(jsonParse(R"(["k1", "v1"])"), R"(["k1", "v1"])");

VELOX_ASSERT_THROW(jsonParse(R"({"k1":})"), "expected json value");
VELOX_ASSERT_THROW(
jsonParse(R"({:"k1"})"), "json parse error on line 0 near `:\"k1\"}");
VELOX_ASSERT_THROW(jsonParse(R"(not_json)"), "expected json value");
jsonParse(R"({"k1":})"), "The JSON document has an improper structure");
VELOX_ASSERT_THROW(
jsonParse(R"({:"k1"})"), "The JSON document has an improper structure");
VELOX_ASSERT_THROW(jsonParse(R"(not_json)"), "Problem while parsing an atom");

EXPECT_EQ(jsonParseWithTry(R"(not_json)"), std::nullopt);
EXPECT_EQ(jsonParseWithTry(R"({"k1":})"), std::nullopt);
Expand All @@ -223,7 +224,7 @@ TEST_F(JsonFunctionsTest, jsonParse) {

VELOX_ASSERT_THROW(
evaluate("json_parse(c0)", data),
"json parse error on line 0 near `:': parsing didn't consume all input");
"missing or superfluous commas, braces, missing keys, etc.");

data = makeRowVector({makeFlatVector<StringView>(
{R"("This is a long sentence")", R"("This is some other sentence")"})});
Expand Down Expand Up @@ -251,6 +252,13 @@ TEST_F(JsonFunctionsTest, jsonParse) {
{R"("This is a long sentence")", R"("This is some other sentence")"},
JSON());
velox::test::assertEqualVectors(expected, result);

try {
jsonParse(R"({"k1":})");
FAIL() << "Error expected";
} catch (const VeloxUserError& e) {
ASSERT_EQ(e.context(), "json_parse(c0)");
}
}

TEST_F(JsonFunctionsTest, isJsonScalarSignatures) {
Expand Down