Parquet¶

BLUE supports ingesting data into BLUE from Parquet files. However, because it is an open-source column-oriented data storage format, you may want to retain your data on foreign Parquet files instead of ingesting it into BLUE. BLUE supports executing queries on foreign Parquet files.

Foreign Data Wrapper Prerequisites¶

Before proceeding, ensure the following Foreign Data Wrapper (FDW) prerequisites:

File Existence: Verify that the file you are ingesting data from exists at the specified path.
Path Accuracy: Confirm that all path elements are present and correctly spelled. Any inaccuracies may lead to data retrieval issues.
Bucket Access Permissions: Ensure that you have the necessary access permissions to the bucket from which you are ingesting data. Lack of permissions can hinder the data retrieval process.
Wildcard Accuracy: If using wildcards, double-check their spelling and configuration. Misconfigured wildcards may result in unintended data ingestion.

Preparing Your Parquet Files¶

Prepare your source Parquet files according to the requirements described in the following table:

BLUE Type → Parquet Source ↓	`BOOL`	`SMALLINT`	`INT`	`BIGINT`	`REAL`	`DOUBLE`	`TEXT` [1]	`DATETIME`
`BOOLEAN`	Supported
`INT16`		Supported
`INT32`			Supported
`INT64`				Supported
`FLOAT`					Supported
`DOUBLE`						Supported
`BYTE_ARRAY` / `FIXED_LEN_BYTE_ARRAY` [2]							Supported
`INT96` [3]								Supported [4]

Your statements will succeed even if your Parquet file contains an unsupported type, such as enum, uuid, time, json, bson, lists, maps, but the data is not referenced in the table (it does not appear in the SELECT query). If the column containing the unsupported type is referenced, an error message is displayed explaining that the type is not supported and that the column may be ommitted. For solutions to this error message, see more information in Managing Unsupported Column Types example in the Example section.

Footnotes

Creating a Table¶

Before loading data, you must build the CREATE TABLE to correspond with the file structure of the inserted table.

The example in this section is based on the source nba.parquet table shown below:

nba.parquet¶
Name	Team	Number	Position	Age	Height	Weight	College	Salary
Avery Bradley	Boston Celtics	0	PG	25	44714	180	Texas	7730337
Jae Crowder	Boston Celtics	99	SF	25	44718	235	Marquette	6796117
John Holland	Boston Celtics	30	SG	27	44717	205	Boston University
R.J. Hunter	Boston Celtics	28	SG	22	44717	185	Georgia State	1148640
Jonas Jerebko	Boston Celtics	8	PF	29	44722	231		5000000
Amir Johnson	Boston Celtics	90	PF	29	44721	240		12000000
Jordan Mickey	Boston Celtics	55	PF	21	44720	235	LSU	1170960
Kelly Olynyk	Boston Celtics	41	C	25	36708	238	Gonzaga	2165160
Terry Rozier	Boston Celtics	12	PG	22	44714	190	Louisville	1824360

The following example shows the correct file structure used to create the CREATE FOREIGN TABLE statement based on the nba.parquet table:

CREATE FOREIGN TABLE ext_nba (
  Name TEXT,
  Team TEXT,
  Number BIGINT,
  Position TEXT,
  Age BIGINT,
  Height TEXT,
  Weight BIGINT,
  College TEXT,
  Salary FLOAT
)
WRAPPER
  parquet_fdw
OPTIONS
  (LOCATION = 's3://sqream-docs/nba.parquet');

Tip

An exact match must exist between the BLUE and Parquet types. For unsupported column types, you can set the type to any type and exclude it from subsequent queries.

Note

The nba.parquet file is stored on S3 at s3://sqream-demo-data/nba.parquet.

Best Practices¶

Because foreign tables do not automatically verify the file integrity or structure, BLUE recommends manually verifying your table output when ingesting Parquet files into BLUE. This lets you determine if your table output is identical to your originally inserted table.

The following is an example of the output based on the nba.parquet table:

SELECT * FROM ext_nba LIMIT 10;

Name          | Team           | Number | Position | Age | Height | Weight | College           | Salary
--------------+----------------+--------+----------+-----+--------+--------+-------------------+---------
Avery Bradley | Boston Celtics |      0 | PG       |  25 | 6-2    |    180 | Texas             |  7730337
Jae Crowder   | Boston Celtics |     99 | SF       |  25 | 6-6    |    235 | Marquette         |  6796117
John Holland  | Boston Celtics |     30 | SG       |  27 | 6-5    |    205 | Boston University |
R.J. Hunter   | Boston Celtics |     28 | SG       |  22 | 6-5    |    185 | Georgia State     |  1148640
Jonas Jerebko | Boston Celtics |      8 | PF       |  29 | 6-10   |    231 |                   |  5000000
Amir Johnson  | Boston Celtics |     90 | PF       |  29 | 6-9    |    240 |                   | 12000000
Jordan Mickey | Boston Celtics |     55 | PF       |  21 | 6-8    |    235 | LSU               |  1170960
Kelly Olynyk  | Boston Celtics |     41 | C        |  25 | 7-0    |    238 | Gonzaga           |  2165160
Terry Rozier  | Boston Celtics |     12 | PG       |  22 | 6-2    |    190 | Louisville        |  1824360
Marcus Smart  | Boston Celtics |     36 | PG       |  22 | 6-4    |    220 | Oklahoma State    |  3431040

Note

If your table output has errors, verify that the structure of the Parquet files correctly corresponds to the foreign table structure that you created.