Parquet Import

To read data from a Parquet file, use the read_parquet function in the FROM clause of a query:

SQL

SELECT * FROM read_parquet('input.parquet');

 id | name  | value
----+-------+-------
  1 | alpha |    10
  2 | beta  |    20

Alternatively, you can omit the read_parquet function and let SereneDB infer the format from the file name:

SQL

SELECT * FROM 'input.parquet';

 id | name  | value
----+-------+-------
  1 | alpha |    10
  2 | beta  |    20

To create a new table using the result from a query, use the CREATE TABLE ... AS SELECT statement:

SQL

CREATE TABLE new_tbl AS    SELECT * FROM read_parquet('input.parquet');

To load data into an existing table from a query, use INSERT INTO from a SELECT statement:

SQL

INSERT INTO tbl    SELECT * FROM read_parquet('input.parquet');

Alternatively, use the COPY statement to load data from a Parquet file into an existing table:

SQL

COPY tbl FROM 'input.parquet' (FORMAT parquet);

Adjusting the Schema on the Fly

You can load a Parquet file into a slightly different schema (e.g., different number of columns, more relaxed types) using the following trick.

Suppose you have a Parquet file with two columns, c1 and c2:

SQL

COPY (FROM (VALUES (42, 43)) t(c1, c2))TO 'f.parquet';

To add another column c3 that is not present in the file, run:

SQL

FROM (VALUES (NULL::VARCHAR, NULL, NULL)) t(c1, c2, c3)WHERE falseUNION ALL BY NAMEFROM 'f.parquet';

 c1 | c2 | c3
----+----+------
 42 | 43 | NULL

The first FROM clause generates an empty table with three columns where c1 is a VARCHAR. UNION ALL BY NAME then appends the rows from the Parquet file, matching them by column name and leaving c3 as NULL since it is absent there.

For additional options, see the Parquet loading reference.