COPY
Examples
Read a CSV file into the lineitem table, using auto-detected CSV options:
COPY lineitem FROM 'lineitem.csv';Read a CSV file into the lineitem table, using manually specified CSV options:
COPY lineitem FROM 'lineitem.csv' (DELIMITER '|');Read a Parquet file into the lineitem table:
COPY lineitem FROM 'lineitem.pq' (FORMAT parquet);Read a JSON file into the lineitem table, using auto-detected options:
COPY lineitem FROM 'lineitem.json' (FORMAT json, AUTO_DETECT true);Read a CSV file into the lineitem table, using double quotes:
COPY lineitem FROM "lineitem.csv";Write a table to a CSV file:
COPY lineitem TO 'lineitem.csv' (FORMAT csv, DELIMITER '|', HEADER);Write a table to a CSV file, using double quotes:
COPY lineitem TO "lineitem.csv";Write the result of a query to a Parquet file:
COPY (SELECT l_orderkey, l_partkey FROM lineitem) TO 'lineitem.parquet' (COMPRESSION zstd);Copy the entire content of database db1 to database db2:
COPY FROM DATABASE db1 TO db2;Copy only the schema (catalog elements) but not any data:
COPY FROM DATABASE db1 TO db2 (SCHEMA);Overview
COPY moves data between SereneDB and external files. COPY ... FROM imports data into SereneDB from an external file. COPY ... TO writes data from SereneDB to an external file. The COPY command can be used for CSV, PARQUET and JSON files.
COPY ... FROM
COPY ... FROM imports data from an external file into an existing table. The data is appended to whatever data is in the table already. The amount of columns inside the file must match the amount of columns in the table tbl, and the contents of the columns must be convertible to the column types of the table. In case this is not possible, an error will be thrown.
If a list of columns is specified, COPY will only copy the data in the specified columns from the file. If there are any columns in the table that are not in the column list, COPY ... FROM will insert the default values for those columns.
Copy the contents of a comma-separated file test.csv without a header into the table test:
COPY test FROM 'test.csv';Copy the contents of a comma-separated file with a header into the category table:
COPY category FROM 'categories.csv' (HEADER);Copy the contents of lineitem.tbl into the lineitem table, where the contents are delimited by a pipe character (|):
COPY lineitem FROM 'lineitem.tbl' (DELIMITER '|');Copy the contents of lineitem.tbl into the lineitem table, where the delimiter, quote character, and presence of a header are automatically detected:
COPY lineitem FROM 'lineitem.tbl' (AUTO_DETECT true);Read the contents of a comma-separated file names.csv into the name column of the category table. Any other columns of this table are filled with their default value:
COPY category(name) FROM 'names.csv';Read the contents of a Parquet file lineitem.parquet into the lineitem table:
COPY lineitem FROM 'lineitem.parquet' (FORMAT parquet);Read the contents of a newline-delimited JSON file lineitem.ndjson into the lineitem table:
COPY lineitem FROM 'lineitem.ndjson' (FORMAT json);Read the contents of a JSON file lineitem.json into the lineitem table:
COPY lineitem FROM 'lineitem.json' (FORMAT json, ARRAY true);An expression may be used as the source of a COPY ... FROM command if it is placed within parentheses.
Read the contents of a file whose path is stored in a variable into the lineitem table:
SET VARIABLE source_file = 'lineitem.json';
COPY lineitem FROM (getvariable('source_file'));Read the contents of a file provided as parameter of a prepared statement into the lineitem table:
PREPARE v1 AS COPY lineitem FROM ($1);
EXECUTE v1('lineitem.json');Syntax
To ensure compatibility with PostgreSQL, SereneDB accepts
COPY ... FROMstatements that do not fully comply with the railroad diagram shown here. For example, the following is a valid statement:COPY tbl FROM 'tbl.csv' WITH DELIMITER '|' CSV HEADER;
COPY ... TO
COPY ... TO exports data from SereneDB to an external CSV, Parquet, JSON or BLOB file. It has mostly the same set of options as COPY ... FROM, however, in the case of COPY ... TO the options specify how the file should be written to disk. Any file created by COPY ... TO can be copied back into the database by using COPY ... FROM with a similar set of options.
The COPY ... TO function can be called specifying either a table name, or a query. When a table name is specified, the contents of the entire table will be written into the resulting file. When a query is specified, the query is executed and the result of the query is written to the resulting file.
Copy the contents of the lineitem table to a CSV file with a header:
COPY lineitem TO 'lineitem.csv';Copy the contents of the lineitem table to the file lineitem.tbl, where the columns are delimited by a pipe character (|), including a header line:
COPY lineitem TO 'lineitem.tbl' (DELIMITER '|');Use tab separators to create a TSV file without a header:
COPY lineitem TO 'lineitem.tsv' (DELIMITER '\t', HEADER false);Copy the l_orderkey column of the lineitem table to the file orderkey.tbl:
COPY lineitem(l_orderkey) TO 'orderkey.tbl' (DELIMITER '|');Copy the result of a query to the file query.csv, including a header with column names:
COPY (SELECT 42 AS a, 'hello' AS b) TO 'query.csv' (DELIMITER ',');Copy the result of a query to the Parquet file query.parquet:
COPY (SELECT 42 AS a, 'hello' AS b) TO 'query.parquet' (FORMAT parquet);Copy the result of a query to the newline-delimited JSON file query.ndjson:
COPY (SELECT 42 AS a, 'hello' AS b) TO 'query.ndjson' (FORMAT json);Copy the result of a query to the JSON file query.json:
COPY (SELECT 42 AS a, 'hello' AS b) TO 'query.json' (FORMAT json, ARRAY true);The RETURN_STATS option makes COPY ... TO return one row per written file, including the filename, row count, the file and footer sizes in bytes, per-column statistics (min, max, null count and size) and any partition keys:
COPY (SELECT l_orderkey, l_comment FROM lineitem) TO 'lineitem_part.parquet' (RETURN_STATS);Note: for nested columns (e.g., structs) the column statistics are defined for each part. For example, if we have a column name STRUCT(field1 INTEGER, field2 INTEGER) the column statistics will have stats for name.field1 and name.field2.
An expression may be used as the target of a COPY ... TO command if it is placed within parentheses.
Copy the result of a query to a file whose path is stored in a variable:
SET VARIABLE target_file = 'target_file.parquet';
COPY (SELECT 'hello world') TO (getvariable('target_file'));Copy to a file provided as parameter of a prepared statement:
PREPARE v1 AS COPY (SELECT 42 AS i) TO $1;
EXECUTE v1('file.csv');Expressions may be used for options as well. Copy to a file using a format stored in a variable:
SET VARIABLE my_format = 'parquet';
COPY (SELECT 42 AS i) TO 'file' (FORMAT getvariable('my_format'));COPY ... TO Options
Zero or more copy options may be provided as a part of the copy operation. The WITH specifier is optional, but if any options are specified, the parentheses are required. Parameter values can be passed in with or without wrapping in single quotes. Arbitrary expressions may be used for parameter values.
Any option that is a Boolean can be enabled or disabled in multiple ways. You can write true, ON, or 1 to enable the option, and false, OFF, or 0 to disable it. The BOOLEAN value can also be omitted, e.g., by only passing (HEADER), in which case true is assumed.
With few exceptions, the below options are applicable to all formats written with COPY.
| Name | Description | Type | Default |
|---|---|---|---|
FORMAT | Specifies the copy function to use. The default is selected from the file extension (e.g., .parquet results in a Parquet file being written/read). If the file extension is unknown CSV is selected. SereneDB provides the CSV, PARQUET and JSON copy functions. | VARCHAR | auto |
USE_TMP_FILE | Whether or not to write to a temporary file first if the original file exists (target.csv.tmp). This prevents overwriting an existing file with a broken file in case the writing is cancelled. | BOOL | auto |
OVERWRITE_OR_IGNORE | Whether or not to allow overwriting files if they already exist. Only has an effect when used with PARTITION_BY. | BOOL | false |
OVERWRITE | When true, all existing files inside targeted directories will be removed (not supported on remote filesystems). Only has an effect when used with PARTITION_BY. | BOOL | false |
APPEND | When true, in the event a filename pattern is generated that already exists, the path will be regenerated to ensure no existing files are overwritten. Only has an effect when used with PARTITION_BY. | BOOL | false |
FILENAME_PATTERN | Set a pattern to use for the filename, can optionally contain {uuid} / {uuidv4} or {uuidv7} to be filled in with a generated UUID (v4 or v7, respectively), and {i}, which is replaced by an incrementing index. Only has an effect when used with PARTITION_BY. | VARCHAR | auto |
FILE_EXTENSION | Set the file extension that should be assigned to the generated file(s). | VARCHAR | auto |
PER_THREAD_OUTPUT | When true, the COPY command generates one file per thread, rather than one file in total. This allows for faster parallel writing. | BOOL | false |
FILE_SIZE_BYTES | If this parameter is set, the COPY process creates a directory which will contain the exported files. If a file exceeds the set limit (specified as bytes such as 1000 or in human-readable format such as 1k), the process creates a new file in the directory. This parameter works in combination with PER_THREAD_OUTPUT. Note that the size is used as an approximation, and files can be occasionally slightly over the limit. | VARCHAR or BIGINT | (empty) |
PARTITION_BY | The columns to partition by using a Hive partitioning scheme, see the partitioned writes section. | VARCHAR[] | (empty) |
PRESERVE_ORDER | Whether or not to preserve order during the copy operation. Defaults to the value of the preserve_insertion_order configuration option. | BOOL | (*) |
RETURN_FILES | Whether or not to include the created filepath(s) (as a files VARCHAR[] column) in the query result. | BOOL | false |
RETURN_STATS | Whether or not to return the files and their column statistics that were written as part of the COPY statement. | BOOL | false |
WRITE_PARTITION_COLUMNS | Whether or not to write partition columns into files. Only has an effect when used with PARTITION_BY. | BOOL | false |
Syntax
COPY FROM DATABASE ... TO
The COPY FROM DATABASE ... TO statement copies the entire content from one attached database to another attached database. This includes the schema, including constraints, indexes, sequences, macros and the data itself.
ATTACH 'db1.db' AS db1;
CREATE TABLE db1.tbl AS SELECT 42 AS x, 3 AS y;
CREATE MACRO db1.two_x_plus_y(x, y) AS 2 * x + y;
ATTACH 'db2.db' AS db2;
COPY FROM DATABASE db1 TO db2;
SELECT db2.two_x_plus_y(x, y) AS z FROM db2.tbl; z---- 87To only copy the schema of db1 to db2 but omit copying the data, add SCHEMA to the statement:
COPY FROM DATABASE db31 TO db32 (SCHEMA);
DETACH IF EXISTS db31;
DETACH IF EXISTS db32;Syntax
Format-Specific Options
CSV Options
The below options are applicable when writing CSV files.
| Name | Description | Type | Default |
|---|---|---|---|
COMPRESSION | The compression type for the file. By default this will be detected automatically from the file extension (e.g., file.csv.gz will use gzip, file.csv.zst will use zstd, and file.csv will use none). Options are none, gzip, zstd. | VARCHAR | auto |
DATEFORMAT | Specifies the date format to use when writing dates. See Date Format. | VARCHAR | (empty) |
DELIM or SEP | The character that is written to separate columns within each row. | VARCHAR | , |
ESCAPE | The character that should appear before a character that matches the quote value. | VARCHAR | " |
FORCE_QUOTE | The list of columns to always add quotes to, even if not required. | VARCHAR[] | [] |
HEADER | Whether or not to write a header for the CSV file. | BOOL | true |
NULLSTR | The string that is written to represent a NULL value. | VARCHAR | (empty) |
PREFIX | Prefixes the CSV file with a specified string. This option must be used in conjunction with SUFFIX and requires HEADER to be set to false. | VARCHAR | (empty) |
SUFFIX | Appends a specified string as a suffix to the CSV file. This option must be used in conjunction with PREFIX and requires HEADER to be set to false. | VARCHAR | (empty) |
QUOTE | The quoting character to be used when a data value is quoted. | VARCHAR | " |
TIMESTAMPFORMAT | Specifies the date format to use when writing timestamps. See Date Format. | VARCHAR | (empty) |
Parquet Options
The below options are applicable when writing Parquet files.
| Name | Description | Type | Default |
|---|---|---|---|
COMPRESSION | The compression format to use (uncompressed, snappy, gzip, zstd, brotli, lz4, lz4_raw). | VARCHAR | snappy |
COMPRESSION_LEVEL | Compression level, set between 1 (lowest compression, fastest) and 22 (highest compression, slowest). Only supported for zstd compression. | BIGINT | 3 |
FIELD_IDS | The field_id for each column. Pass auto to attempt to infer automatically. | STRUCT | (empty) |
ROW_GROUP_SIZE_BYTES | The target size of each row group. You can pass either a human-readable string, e.g., 2MB, or an integer, i.e., the number of bytes. This option is only used when you have issued SET preserve_insertion_order = false;, otherwise, it is ignored. | BIGINT | row_group_size * 1024 |
ROW_GROUP_SIZE | The target size, i.e., number of rows, of each row group. | BIGINT | 122880 |
ROW_GROUPS_PER_FILE | Create a new Parquet file if the current one has a specified number of row groups. If multiple threads are active, the number of row groups in a file may slightly exceed the specified number of row groups to limit the amount of locking – similarly to the behavior of FILE_SIZE_BYTES. However, if per_thread_output is set, only one thread writes to each file, and it becomes accurate again. | BIGINT | (empty) |
PARQUET_VERSION | The Parquet version to use (V1, V2). | VARCHAR | V1 |
Some examples of FIELD_IDS are as follows.
Assign field_ids automatically:
COPY (SELECT 128 AS i) TO 'my.parquet' (FIELD_IDS 'auto');Sets the field_id of column i to 42:
COPY (SELECT 128 AS i) TO 'my.parquet' (FIELD_IDS {i: 42});Sets the field_id of column i to 42, and column j to 43:
COPY (SELECT 128 AS i, 256 AS j) TO 'my.parquet' (FIELD_IDS {i: 42, j: 43});Sets the field_id of column my_struct to 42, and column i (nested inside my_struct) to 43:
COPY (SELECT {i: 128} AS my_struct) TO 'my.parquet' (FIELD_IDS {my_struct: {__duckdb_field_id: 42, i: 43}});Sets the field_id of column my_list to 42, and column element (default name of list child) to 43:
COPY (SELECT [128, 256] AS my_list) TO 'my.parquet' (FIELD_IDS {my_list: {__duckdb_field_id: 42, element: 43}});Sets the field_id of column my_map to 42, and columns key and value (default names of map children) to 43 and 44:
COPY (SELECT MAP {'key1' : 128, 'key2': 256} my_map) TO 'my.parquet' (FIELD_IDS {my_map: {__duckdb_field_id: 42, key: 43, value: 44}});JSON Options
The below options are applicable when writing JSON files.
| Name | Description | Type | Default |
|---|---|---|---|
ARRAY | Whether to write a JSON array. If true, a JSON array of records is written, if false, newline-delimited JSON is written | BOOL | false |
COMPRESSION | The compression type for the file. By default this will be detected automatically from the file extension (e.g., file.json.gz will use gzip, file.json.zst will use zstd, and file.json will use none). Options are none, gzip, zstd. | VARCHAR | auto |
DATEFORMAT | Specifies the date format to use when writing dates. See Date Format. | VARCHAR | (empty) |
TIMESTAMPFORMAT | Specifies the date format to use when writing timestamps. See Date Format. | VARCHAR | (empty) |
Sets the value of column hello to HELLO! and outputs the results to hello.json:
COPY (SELECT 'HELLO!' AS hello) TO 'hello.json';Sets the value of column num_list to [1,2,3] and outputs the results to numbers.json:
COPY (SELECT [1, 2, 3] AS num_list) TO 'numbers.json';Sets the value of column compression_type to gzip_explicit and outputs the results to compression.json.gz with explicit compression:
COPY (SELECT 'gzip_explicit' AS compression_type) TO 'explicit_compression.json' (FORMAT json, COMPRESSION 'GZIP');Sets all values of single rows to be returned as nested arrays to array_true.json:
COPY (SELECT 1 AS id, 'Alice' AS name, [1, 2, 3] AS numbers UNION ALL SELECT 2, 'Bob', [4, 5, 6] AS numbers)TO 'array_true.json' (FORMAT json, ARRAY true);Sets all values of single rows to be returned as non-nested arrays to array_false.json:
COPY (SELECT 1 AS id, 'Alice' AS name, [1, 2, 3] AS numbers UNION ALL SELECT 2, 'Bob', [4, 5, 6] AS numbers)TO 'array_false.json' (FORMAT json, ARRAY false);BLOB Options
The BLOB format option allows you to select a single column of a SereneDB table into a .blob file.
The column must be cast to the BLOB data type. For details on typecasting, see the
Casting Operations Matrix.
The below options are applicable when writing BLOB files.
| Name | Description | Type | Default |
|---|---|---|---|
COMPRESSION | The compression type for the file. By default this will be detected automatically from the file extension (e.g., file.blob.gz will use gzip, file.blob.zst will use zstd, and file.blob will use none). Options are none, gzip, zstd. | VARCHAR | auto |
Type casts the string value foo to the BLOB data type and outputs the results to blob_output.blob:
COPY (select 'foo'::BLOB) TO 'blob_output.blob' (FORMAT BLOB);Type casts the string value foo to the BLOB data type and outputs the results to blob_output_gzip.blob.gz with gzip compression:
COPY (select 'foo'::BLOB) TO 'blob_output_gzip.blob' (FORMAT BLOB, COMPRESSION 'GZIP');Limitations
COPY does not support copying between tables. To copy between tables, use an INSERT statement:
INSERT INTO tbl2 FROM tbl1;
DETACH IF EXISTS db13;
DETACH IF EXISTS db14;