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Merged
lidavidm merged 5 commits into from
Oct 5, 2026
Merged

feat(c/driver/postgresql): expose numeric result type modifiers #4798

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cc04e96
feat(c/driver/postgresql): expose numeric result type modifiers
besquared Sep 22, 2026
61ba8ed
style(c/driver/postgresql): group numeric modifier with type name
besquared Sep 22, 2026
4701b5f
docs(c/driver/postgresql): link numeric type modifier references
besquared Sep 22, 2026
f0d0339
docs(c/driver/postgresql): align numeric metadata documentation style
besquared Sep 22, 2026
c815741
docs(c/driver/postgresql): simplify result metadata reference
besquared Oct 3, 2026
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14 changes: 14 additions & 0 deletions c/driver/postgresql/postgres_type.h
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@

#include <cerrno>
#include <cstdint>
#include <optional>
#include <string>
#include <unordered_map>
#include <utility>
Expand Down Expand Up @@ -166,6 +167,12 @@ class PostgresType {
return out;
}

PostgresType WithTypeModifier(int32_t typmod) const {
PostgresType out(*this);
out.typmod_ = typmod;
return out;
}

PostgresType Array(uint32_t oid = 0, const std::string& typname = "") const {
PostgresType out(PostgresTypeId::kArray);
out.AppendChild("item", *this);
Expand Down Expand Up @@ -371,11 +378,13 @@ class PostgresType {
uint32_t oid_;
PostgresTypeId type_id_;
std::string typname_;
std::optional<int32_t> typmod_;
std::string field_name_;
std::vector<PostgresType> children_;

static constexpr const char* kPostgresTypeKey = "ADBC:postgresql:typname";
static constexpr const char* kTypeKey = "POSTGRESQL:type";
static constexpr const char* kTypeModifierKey = "POSTGRESQL:typmod";
static constexpr const char* kExtensionName = "ARROW:extension:name";
static constexpr const char* kOpaqueExtensionName = "arrow.opaque";
static constexpr const char* kJsonExtensionName = "arrow.json";
Expand All @@ -389,6 +398,11 @@ class PostgresType {
NANOARROW_RETURN_NOT_OK(ArrowMetadataBuilderInit(buffer.get(), schema->metadata));
NANOARROW_RETURN_NOT_OK(ArrowMetadataBuilderAppend(
buffer.get(), ArrowCharView(kTypeKey), ArrowCharView(typname)));
if (type_id_ == PostgresTypeId::kNumeric && typmod_.has_value()) {
const std::string typmod = std::to_string(*typmod_);
NANOARROW_RETURN_NOT_OK(ArrowMetadataBuilderAppend(
buffer.get(), ArrowCharView(kTypeModifierKey), ArrowCharView(typmod.c_str())));
}
NANOARROW_RETURN_NOT_OK(
ArrowSchemaSetMetadata(schema, reinterpret_cast<char*>(buffer->data)));
return NANOARROW_OK;
Expand Down
33 changes: 33 additions & 0 deletions c/driver/postgresql/postgres_type_test.cc
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Expand Up @@ -29,6 +29,39 @@

namespace adbcpq {

TEST(PostgresTypeTest, NumericTypeModifier) {
for (const int32_t typmod : {-1, 1900557, 329729, 131080}) {
SCOPED_TRACE(typmod);
nanoarrow::UniqueSchema schema;
ArrowSchemaInit(schema.get());
ASSERT_EQ(PostgresType(PostgresTypeId::kNumeric)
.WithTypeModifier(typmod)
.WithFieldName("amount")
.SetSchema(schema.get()),
NANOARROW_OK);
EXPECT_STREQ(schema->format, "u");
EXPECT_STREQ(schema->name, "amount");
ArrowStringView value = ArrowCharView("");
ASSERT_EQ(ArrowMetadataGetValue(schema->metadata, ArrowCharView("POSTGRESQL:typmod"),
&value),
NANOARROW_OK);
EXPECT_EQ(std::string(value.data, value.size_bytes), std::to_string(typmod));
ASSERT_EQ(ArrowMetadataGetValue(schema->metadata,
ArrowCharView("ARROW:extension:name"), &value),
NANOARROW_OK);
EXPECT_EQ(std::string(value.data, value.size_bytes), "arrow.opaque");
}

nanoarrow::UniqueSchema schema;
ArrowSchemaInit(schema.get());
ASSERT_EQ(PostgresType(PostgresTypeId::kNumeric).SetSchema(schema.get()), NANOARROW_OK);
ArrowStringView value = {nullptr, 0};
ASSERT_EQ(
ArrowMetadataGetValue(schema->metadata, ArrowCharView("POSTGRESQL:typmod"), &value),
NANOARROW_OK);
EXPECT_EQ(value.data, nullptr);
}

class MockTypeResolver : public PostgresTypeResolver {
public:
ArrowErrorCode Init() {
Expand Down
55 changes: 55 additions & 0 deletions c/driver/postgresql/postgresql_test.cc
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Expand Up @@ -2042,6 +2042,61 @@ TEST_F(PostgresStatementTest, ExecuteSchemaParameterizedQuery) {
ASSERT_THAT(AdbcStatementRelease(&statement, &error), IsOkStatus(&error));
}

TEST_F(PostgresStatementTest, NumericTypeModifier) {
ASSERT_THAT(AdbcStatementNew(&connection, &statement, &error), IsOkStatus(&error));
for (const char* use_copy : {"true", "false"}) {
SCOPED_TRACE(use_copy);
ASSERT_THAT(
AdbcStatementSetOption(&statement, "adbc.postgresql.use_copy", use_copy, &error),
IsOkStatus(&error));
for (const char* predicate : {"true", "false"}) {
SCOPED_TRACE(predicate);
const std::string query =
"SELECT 1.25::numeric(29,9), 1.25::numeric, NULL::numeric(29,9), "
"1.25::numeric(29,9) + 1.25::numeric(29,9), 1::integer WHERE "s +
predicate;
ASSERT_THAT(AdbcStatementSetSqlQuery(&statement, query.c_str(), &error),
IsOkStatus(&error));
nanoarrow::UniqueSchema described;
ASSERT_THAT(AdbcStatementExecuteSchema(&statement, described.get(), &error),
IsOkStatus(&error));
adbc_validation::StreamReader reader;
ASSERT_THAT(AdbcStatementExecuteQuery(&statement, &reader.stream.value,
&reader.rows_affected, &error),
IsOkStatus(&error));
ASSERT_NO_FATAL_FAILURE(reader.GetSchema());
for (const ArrowSchema* schema : {described.get(), &reader.schema.value}) {
ASSERT_EQ(schema->n_children, 5);
for (int i = 0; i < 5; i++) {
ArrowStringView value = {nullptr, 0};
ASSERT_EQ(ArrowMetadataGetValue(schema->children[i]->metadata,
ArrowCharView("POSTGRESQL:typmod"), &value),
NANOARROW_OK);
if (i == 4) {
EXPECT_EQ(value.data, nullptr);
} else {
EXPECT_STREQ(schema->children[i]->format, "u");
EXPECT_EQ(std::string(value.data, value.size_bytes),
(i == 0 || i == 2) ? "1900557" : "-1");
}
}
}
ASSERT_NO_FATAL_FAILURE(reader.Next());
if (std::string(predicate) == "true") {
ASSERT_NE(reader.array->release, nullptr);
ASSERT_NO_FATAL_FAILURE(adbc_validation::CompareArray<std::string>(
reader.array_view->children[0], {"1.250000000"}));
ASSERT_NO_FATAL_FAILURE(adbc_validation::CompareArray<std::string>(
reader.array_view->children[1], {"1.25"}));
ASSERT_NO_FATAL_FAILURE(adbc_validation::CompareArray<std::string>(
reader.array_view->children[2], {std::nullopt}));
ASSERT_NO_FATAL_FAILURE(reader.Next());
}
ASSERT_EQ(reader.array->release, nullptr);
}
}
}

TEST_F(PostgresStatementTest, ExecuteParameterizedQueryWithResult) {
nanoarrow::UniqueSchema schema_bind;
ArrowSchemaInit(schema_bind.get());
Expand Down
3 changes: 2 additions & 1 deletion c/driver/postgresql/result_helper.cc
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Expand Up @@ -183,7 +183,8 @@ Status PqResultHelper::ResolveOutputTypes(PostgresTypeResolver& type_resolver,
pg_type = PostgresType::Unnamed(pg_oid);
}

root_type.AppendChild(PQfname(result_, i), pg_type);
root_type.AppendChild(PQfname(result_, i),
pg_type.WithTypeModifier(PQfmod(result_, i)));
}

*result_types = root_type;
Expand Down
3 changes: 3 additions & 0 deletions c/driver/postgresql/result_helper.h
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Expand Up @@ -169,6 +169,9 @@ class PqResultHelper {
return PQfname(result_, column_number);
}
Oid FieldType(int column_number) const { return PQftype(result_, column_number); }
int FieldTypeModifier(int column_number) const {
return PQfmod(result_, column_number);
}
PqResultRow Row(int i) const { return PqResultRow(result_, i); }

class iterator {
Expand Down
3 changes: 2 additions & 1 deletion c/driver/postgresql/result_reader.cc
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Expand Up @@ -203,7 +203,8 @@ Status PqResultArrayReader::Initialize(int64_t* rows_affected) {
UNWRAP_ERRNO(Internal,
type_resolver_->FindWithDefault(helper_.FieldType(i), &child_type));

child_type = child_type.WithFieldName(helper_.FieldName(i));
child_type = child_type.WithFieldName(helper_.FieldName(i))
.WithTypeModifier(helper_.FieldTypeModifier(i));
UNWRAP_ERRNO(Internal, child_type.SetSchema(schema_->children[i], vendor_name_));

std::unique_ptr<PostgresCopyFieldReader> child_reader;
Expand Down
16 changes: 16 additions & 0 deletions docs/source/driver/postgresql.rst
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@lidavidm lidavidm Sep 24, 2026

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Can you clean up this prose? Stuff like "It does not add modifiers to parameter schemas or catalog discovery." is rather unnecessary; I don't need a full log of the AI's thought process baked into the docs.

@lidavidm lidavidm Sep 24, 2026

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I'd rather have just a section briefly listing the metadata keys we attach and describing each one.

@besquared besquared Sep 28, 2026

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Sorry yeah there's a bunch of slop in here, I wasn't sure this would even come to the attention of folks so I hadn't looked over it closely yet. I'll go back through it as soon as I get some time to return to it.

Original file line number Diff line number Diff line change
Expand Up @@ -299,6 +299,22 @@ being read or written.
overflow/underflow; an error will be returned if this would be
the case.

Result Field Metadata
~~~~~~~~~~~~~~~~~~~~~

The driver attaches the following PostgreSQL metadata to Arrow result fields:

``POSTGRESQL:type``
The PostgreSQL type name, such as ``int4`` or ``numeric``.

``POSTGRESQL:typmod``
The type modifier for a top-level numeric column, returned by
`PQfmod <https://www.postgresql.org/docs/18/libpq-exec.html#LIBPQ-PQFMOD>`_,
as a signed decimal string. Encodes precision and scale using
PostgreSQL's `numeric typmod encoding
<https://github.com/postgres/postgres/blob/REL_18_0/src/backend/utils/adt/numeric.c#L891-L947>`_.
Value is ``-1`` if no modifier is available.

Unknown Types
~~~~~~~~~~~~~

Expand Down
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