Appenders are the most efficient way of loading data into DuckDB from within the C interface, and are recommended for
fast data loading. The appender is much faster than using prepared statements or individual INSERT INTO statements.
Appends are made in row-wise format. For every column, a duckdb_append_[type] call should be made, after which
the row should be finished by calling duckdb_appender_end_row. After all rows have been appended,
duckdb_appender_destroy should be used to finalize the appender and clean up the resulting memory.
Note that duckdb_appender_destroy should always be called on the resulting appender, even if the function returns
DuckDBError.
Example
duckdb_query(con, "CREATE TABLE people (id INTEGER, name VARCHAR)", NULL);
duckdb_appender appender;
if (duckdb_appender_create(con, NULL, "people", &appender) == DuckDBError) {
// handle error
}
// append the first row (1, Mark)
duckdb_append_int32(appender, 1);
duckdb_append_varchar(appender, "Mark");
duckdb_appender_end_row(appender);
// append the second row (2, Hannes)
duckdb_append_int32(appender, 2);
duckdb_append_varchar(appender, "Hannes");
duckdb_appender_end_row(appender);
// finish appending and flush all the rows to the table
duckdb_appender_destroy(&appender);
API Reference Overview
duckdb_state duckdb_appender_create(duckdb_connection connection, const char *schema, const char *table, duckdb_appender *out_appender);
idx_t duckdb_appender_column_count(duckdb_appender appender);
duckdb_logical_type duckdb_appender_column_type(duckdb_appender appender, idx_t col_idx);
const char *duckdb_appender_error(duckdb_appender appender);
duckdb_state duckdb_appender_flush(duckdb_appender appender);
duckdb_state duckdb_appender_close(duckdb_appender appender);
duckdb_state duckdb_appender_destroy(duckdb_appender *appender);
duckdb_state duckdb_appender_begin_row(duckdb_appender appender);
duckdb_state duckdb_appender_end_row(duckdb_appender appender);
duckdb_state duckdb_append_default(duckdb_appender appender);
duckdb_state duckdb_append_bool(duckdb_appender appender, bool value);
duckdb_state duckdb_append_int8(duckdb_appender appender, int8_t value);
duckdb_state duckdb_append_int16(duckdb_appender appender, int16_t value);
duckdb_state duckdb_append_int32(duckdb_appender appender, int32_t value);
duckdb_state duckdb_append_int64(duckdb_appender appender, int64_t value);
duckdb_state duckdb_append_hugeint(duckdb_appender appender, duckdb_hugeint value);
duckdb_state duckdb_append_uint8(duckdb_appender appender, uint8_t value);
duckdb_state duckdb_append_uint16(duckdb_appender appender, uint16_t value);
duckdb_state duckdb_append_uint32(duckdb_appender appender, uint32_t value);
duckdb_state duckdb_append_uint64(duckdb_appender appender, uint64_t value);
duckdb_state duckdb_append_uhugeint(duckdb_appender appender, duckdb_uhugeint value);
duckdb_state duckdb_append_float(duckdb_appender appender, float value);
duckdb_state duckdb_append_double(duckdb_appender appender, double value);
duckdb_state duckdb_append_date(duckdb_appender appender, duckdb_date value);
duckdb_state duckdb_append_time(duckdb_appender appender, duckdb_time value);
duckdb_state duckdb_append_timestamp(duckdb_appender appender, duckdb_timestamp value);
duckdb_state duckdb_append_interval(duckdb_appender appender, duckdb_interval value);
duckdb_state duckdb_append_varchar(duckdb_appender appender, const char *val);
duckdb_state duckdb_append_varchar_length(duckdb_appender appender, const char *val, idx_t length);
duckdb_state duckdb_append_blob(duckdb_appender appender, const void *data, idx_t length);
duckdb_state duckdb_append_null(duckdb_appender appender);
duckdb_state duckdb_append_data_chunk(duckdb_appender appender, duckdb_data_chunk chunk);
duckdb_appender_create
Creates an appender object.
Note that the object must be destroyed with duckdb_appender_destroy.
Syntax
duckdb_state duckdb_appender_create(
duckdb_connection connection,
const char *schema,
const char *table,
duckdb_appender *out_appender
);
Parameters
connection: The connection context to create the appender in.schema: The schema of the table to append to, ornullptrfor the default schema.table: The table name to append to.out_appender: The resulting appender object.
Return Value
DuckDBSuccess on success or DuckDBError on failure.
duckdb_appender_column_count
Returns the number of columns in the table that belongs to the appender.
Syntax
idx_t duckdb_appender_column_count(
duckdb_appender appender
);
Parameters
appender: The appender to get the column count from.
Return Value
The number of columns in the table.
duckdb_appender_column_type
Returns the type of the column at the specified index.
Note: The resulting type should be destroyed with duckdb_destroy_logical_type.
Syntax
duckdb_logical_type duckdb_appender_column_type(
duckdb_appender appender,
idx_t col_idx
);
Parameters
appender: The appender to get the column type from.col_idx: The index of the column to get the type of.
Return Value
The duckdb_logical_type of the column.
duckdb_appender_error
Returns the error message associated with the given appender.
If the appender has no error message, this returns nullptr instead.
The error message should not be freed. It will be de-allocated when duckdb_appender_destroy is called.
Syntax
const char *duckdb_appender_error(
duckdb_appender appender
);
Parameters
appender: The appender to get the error from.
Return Value
The error message, or nullptr if there is none.
duckdb_appender_flush
Flush the appender to the table, forcing the cache of the appender to be cleared. If flushing the data triggers a constraint violation or any other error, then all data is invalidated, and this function returns DuckDBError. It is not possible to append more values. Call duckdb_appender_error to obtain the error message followed by duckdb_appender_destroy to destroy the invalidated appender.
Syntax
duckdb_state duckdb_appender_flush(
duckdb_appender appender
);
Parameters
appender: The appender to flush.
Return Value
DuckDBSuccess on success or DuckDBError on failure.
duckdb_appender_close
Closes the appender by flushing all intermediate states and closing it for further appends. If flushing the data triggers a constraint violation or any other error, then all data is invalidated, and this function returns DuckDBError. Call duckdb_appender_error to obtain the error message followed by duckdb_appender_destroy to destroy the invalidated appender.
Syntax
duckdb_state duckdb_appender_close(
duckdb_appender appender
);
Parameters
appender: The appender to flush and close.
Return Value
DuckDBSuccess on success or DuckDBError on failure.
duckdb_appender_destroy
Closes the appender by flushing all intermediate states to the table and destroying it. By destroying it, this function de-allocates all memory associated with the appender. If flushing the data triggers a constraint violation, then all data is invalidated, and this function returns DuckDBError. Due to the destruction of the appender, it is no longer possible to obtain the specific error message with duckdb_appender_error. Therefore, call duckdb_appender_close before destroying the appender, if you need insights into the specific error.
Syntax
duckdb_state duckdb_appender_destroy(
duckdb_appender *appender
);
Parameters
appender: The appender to flush, close and destroy.
Return Value
DuckDBSuccess on success or DuckDBError on failure.
duckdb_appender_begin_row
A nop function, provided for backwards compatibility reasons. Does nothing. Only duckdb_appender_end_row is required.
Syntax
duckdb_state duckdb_appender_begin_row(
duckdb_appender appender
);
duckdb_appender_end_row
Finish the current row of appends. After end_row is called, the next row can be appended.
Syntax
duckdb_state duckdb_appender_end_row(
duckdb_appender appender
);
Parameters
appender: The appender.
Return Value
DuckDBSuccess on success or DuckDBError on failure.
duckdb_append_default
Append a DEFAULT value (NULL if DEFAULT not available for column) to the appender.
Syntax
duckdb_state duckdb_append_default(
duckdb_appender appender
);
duckdb_append_bool
Append a bool value to the appender.
Syntax
duckdb_state duckdb_append_bool(
duckdb_appender appender,
bool value
);
duckdb_append_int8
Append an int8_t value to the appender.
Syntax
duckdb_state duckdb_append_int8(
duckdb_appender appender,
int8_t value
);
duckdb_append_int16
Append an int16_t value to the appender.
Syntax
duckdb_state duckdb_append_int16(
duckdb_appender appender,
int16_t value
);
duckdb_append_int32
Append an int32_t value to the appender.
Syntax
duckdb_state duckdb_append_int32(
duckdb_appender appender,
int32_t value
);
duckdb_append_int64
Append an int64_t value to the appender.
Syntax
duckdb_state duckdb_append_int64(
duckdb_appender appender,
int64_t value
);
duckdb_append_hugeint
Append a duckdb_hugeint value to the appender.
Syntax
duckdb_state duckdb_append_hugeint(
duckdb_appender appender,
duckdb_hugeint value
);
duckdb_append_uint8
Append a uint8_t value to the appender.
Syntax
duckdb_state duckdb_append_uint8(
duckdb_appender appender,
uint8_t value
);
duckdb_append_uint16
Append a uint16_t value to the appender.
Syntax
duckdb_state duckdb_append_uint16(
duckdb_appender appender,
uint16_t value
);
duckdb_append_uint32
Append a uint32_t value to the appender.
Syntax
duckdb_state duckdb_append_uint32(
duckdb_appender appender,
uint32_t value
);
duckdb_append_uint64
Append a uint64_t value to the appender.
Syntax
duckdb_state duckdb_append_uint64(
duckdb_appender appender,
uint64_t value
);
duckdb_append_uhugeint
Append a duckdb_uhugeint value to the appender.
Syntax
duckdb_state duckdb_append_uhugeint(
duckdb_appender appender,
duckdb_uhugeint value
);
duckdb_append_float
Append a float value to the appender.
Syntax
duckdb_state duckdb_append_float(
duckdb_appender appender,
float value
);
duckdb_append_double
Append a double value to the appender.
Syntax
duckdb_state duckdb_append_double(
duckdb_appender appender,
double value
);
duckdb_append_date
Append a duckdb_date value to the appender.
Syntax
duckdb_state duckdb_append_date(
duckdb_appender appender,
duckdb_date value
);
duckdb_append_time
Append a duckdb_time value to the appender.
Syntax
duckdb_state duckdb_append_time(
duckdb_appender appender,
duckdb_time value
);
duckdb_append_timestamp
Append a duckdb_timestamp value to the appender.
Syntax
duckdb_state duckdb_append_timestamp(
duckdb_appender appender,
duckdb_timestamp value
);
duckdb_append_interval
Append a duckdb_interval value to the appender.
Syntax
duckdb_state duckdb_append_interval(
duckdb_appender appender,
duckdb_interval value
);
duckdb_append_varchar
Append a varchar value to the appender.
Syntax
duckdb_state duckdb_append_varchar(
duckdb_appender appender,
const char *val
);
duckdb_append_varchar_length
Append a varchar value to the appender.
Syntax
duckdb_state duckdb_append_varchar_length(
duckdb_appender appender,
const char *val,
idx_t length
);
duckdb_append_blob
Append a blob value to the appender.
Syntax
duckdb_state duckdb_append_blob(
duckdb_appender appender,
const void *data,
idx_t length
);
duckdb_append_null
Append a NULL value to the appender (of any type).
Syntax
duckdb_state duckdb_append_null(
duckdb_appender appender
);
duckdb_append_data_chunk
Appends a pre-filled data chunk to the specified appender.
The types of the data chunk must exactly match the types of the table, no casting is performed. If the types do not match or the appender is in an invalid state, DuckDBError is returned. If the append is successful, DuckDBSuccess is returned.
Syntax
duckdb_state duckdb_append_data_chunk(
duckdb_appender appender,
duckdb_data_chunk chunk
);
Parameters
appender: The appender to append to.chunk: The data chunk to append.
Return Value
The return state.