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feat(c/include/arrow-adbc): Add AdbcStatementRequestSchema #3623

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Merged
lidavidm merged 7 commits into from
Jul 22, 2026
Merged

feat(c/include/arrow-adbc): Add AdbcStatementRequestSchema #3623

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4dfe808
request schema
paleolimbot Oct 27, 2025
f9cea38
add more language
paleolimbot Oct 27, 2025
6fc5218
remove negotiation garbage
paleolimbot Nov 19, 2025
120da6c
add stub
paleolimbot Feb 25, 2026
d2051a9
maybe put things in the right place
paleolimbot Feb 27, 2026
fb85d96
maybe language on intended column fidelity
paleolimbot Jul 22, 2026
fd08d4b
pre-commit
lidavidm Jul 22, 2026
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21 changes: 21 additions & 0 deletions c/driver_manager/adbc_driver_manager.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1764,6 +1764,12 @@ AdbcStatusCode StatementSetSubstraitPlan(struct AdbcStatement*, const uint8_t*,
return ADBC_STATUS_NOT_IMPLEMENTED;
}

AdbcStatusCode StatementRequestSchema(struct AdbcStatement*, struct ArrowSchema*,
struct AdbcError* error) {
SetError(error, "AdbcStatementRequestSchema not implemented");
return ADBC_STATUS_NOT_IMPLEMENTED;
}

/// Temporary state while the database is being configured.
struct TempDatabase {
std::unordered_map<std::string, std::string> options;
Expand Down Expand Up @@ -3159,6 +3165,17 @@ AdbcStatusCode AdbcStatementSetSubstraitPlan(struct AdbcStatement* statement,
error);
}

AdbcStatusCode AdbcStatementRequestSchema(struct AdbcStatement* statement,
struct ArrowSchema* schema,
struct AdbcError* error) {
if (!statement->private_driver) {
SetError(error, "AdbcStatementRequestSchema: must call AdbcStatementNew first");
return ADBC_STATUS_INVALID_STATE;
}
INIT_ERROR(error, statement);
return statement->private_driver->StatementRequestSchema(statement, schema, error);
}

const char* AdbcStatusCodeMessage(AdbcStatusCode code) {
#define CASE(CONSTANT) \
case ADBC_STATUS_##CONSTANT: \
Expand Down Expand Up @@ -3382,6 +3399,10 @@ AdbcStatusCode AdbcLoadDriverFromInitFunc(AdbcDriverInitFunc init_func, int vers
FILL_DEFAULT(driver, StatementSetOptionDouble);
FILL_DEFAULT(driver, StatementSetOptionInt);
}
if (version >= ADBC_VERSION_1_2_0) {
auto* driver = reinterpret_cast<struct AdbcDriver*>(raw_driver);
FILL_DEFAULT(driver, StatementRequestSchema);
}

return ADBC_STATUS_OK;

Expand Down
37 changes: 37 additions & 0 deletions c/include/arrow-adbc/adbc.h
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Expand Up @@ -1290,6 +1290,9 @@ struct ADBC_EXPORT AdbcDriver {
AdbcStatusCode (*StatementExecuteMulti)(struct AdbcStatement*,
struct AdbcMultiResultSet*, struct AdbcError*);

AdbcStatusCode (*StatementRequestSchema)(struct AdbcStatement*, struct ArrowSchema*,
struct AdbcError*);

/// @}
};

Expand Down Expand Up @@ -2293,6 +2296,40 @@ AdbcStatusCode AdbcStatementExecuteSchema(struct AdbcStatement* statement,
struct ArrowSchema* schema,
struct AdbcError* error);

/// \brief Request the schema of the next statement execution
///
/// Allows the caller to request a specific schema based on prior

@zeroshade zeroshade May 13, 2026

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Should we explicitly define the behavior if columns in the result schema are missing from the requested schema and the reverse (columns in the requested schema missing from the result schema)?

What about column ordering? I'm not making any suggestions about what the behavior should be, just that we should explicitly state what the expected behavior should be in those cases.

@paleolimbot paleolimbot May 13, 2026

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Good point...I will try to update the text tonight. Off the top of my head the ability to request a schema with more columns than the source or in a different order is useful, as is widening the allowed nullability. Requesting fewer columns is fishy. DataFusion has quite a nice programmatic definition of this (designed for casting struct columns to match each other, possibly from multiple Parquet files).

@lidavidm lidavidm Jul 20, 2026

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What's the status here?

Personally I'm fine saying that you have to match (at least to start), though allowing widened nullability seems fine, and if there's a use case we can define the rest. Reordering columns and such to me starts to feel like #13 a bit. If only everyone supported Substrait, things would be easy :P

@paleolimbot paleolimbot Jul 20, 2026

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I forgot about this...I'll put the language in sometime today. The intention is to align types in place for drivers where the inferred destination type is arbitrary, not to reorder (which places responsibility on the driver that's currently tricky to satisfy in C or C++).

/// information or user input. This may be used to ensure a
/// consistent schema when executing queries against a database
/// with row-based types (e.g., SQLite) or a database whose types
/// are implemented with row-based parameters where Arrow prefers
/// type-level parameters (e.g., NUMERIC for PostgreSQL). The
/// schema request is intended to modify only the types or
/// widen the nullability of types in the original schema;
/// column reordering or changing the number of returned columns
/// is not a goal of this feature.
///
/// The provided schema is a request and not a guarantee (i.e.,
/// callers must use the schema provided by the output stream to
/// interpret the result).
///
/// Calling AdbcStatementRequestSchema() must not affect the result
/// of AdbcStatementExecuteSchema (which always infers its result
/// from the input query).
///
/// \since ADBC API revision 1.2.0
///
/// \param[in] statement The statement to execute.
/// \param[in] schema The requested schema.
/// \param[out] error An optional location to return an error
/// message if necessary.
///
/// \return ADBC_STATUS_NOT_IMPLEMENTED if the driver does not support this.
ADBC_EXPORT
AdbcStatusCode AdbcStatementRequestSchema(struct AdbcStatement* statement,
struct ArrowSchema* schema,
struct AdbcError* error);

/// \brief Turn this statement into a prepared statement to be
/// executed multiple times.
///
Expand Down
21 changes: 21 additions & 0 deletions go/adbc/drivermgr/adbc_driver_manager.cc
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37 changes: 37 additions & 0 deletions go/adbc/drivermgr/arrow-adbc/adbc.h
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