To view the schema of your Parquet data, use the READ_NOS table operator with the RETURNTYPE('NOSREAD_SCHEMA') or the RETURNTYPE('NOSREAD_PARQUET_SCHEMA') clause.
The examples and results show a sample river flow data set. To use your own data, replace the table and column names, and authorization object.
- To run NOS-related commands, log on to the database as a user with the required privileges.
- View the schema of the Parquet data:
SELECT * FROM ( LOCATION='YOUR-OBJECT-STORE-URI' AUTHORIZATION=authorization_object RETURNTYPE='NOSREAD_SCHEMA' ) AS d;
See Variable Substitutions for Examples for the credentials and location values for the sample river flow data set.
Your result will be similar to the following:
ColPosition 1 Name GageHeight2 TdatDataType FLOAT PhysicalType DOUBLE LogicalType NONE Precision 0 Scale 0 MinLength 0 MaxLength 0 NullFound 1 FileType parquet Location /S3/s3.amazonaws.com/td-usgs-public/PARQUETDATA/ ColPosition 2 Name Flow TdatDataType FLOAT PhysicalType DOUBLE LogicalType NONE Precision 0 Scale 0 MinLength 0 MaxLength 0 NullFound 1 FileType parquet Location /S3/s3.amazonaws.com/td-usgs-public/PARQUETDATA/ [...]The output is displayed vertically for readability.
Or, you can view the schema using NOSREAD_PARQUET_SCHEMA, if you are using the FULLSCAN option. The FULLSCAN option is used to scan columns of variable length types to get the maximum length:
SELECT * FROM ( LOCATION='YOUR-OBJECT-STORE-URI' AUTHORIZATION=authorization_object FULLSCAN='TRUE' RETURNTYPE='NOSREAD_PARQUET_SCHEMA' ) AS d;
Your result will be similar to the following:
ColPosition 1 Name GageHeight2 TdatDataType FLOAT PhysicalType DOUBLE LogicalType NONE Precision 0 Scale 0 MinLength 0 MaxLength 0 NullFound 1 FileType parquet Location /S3/s3.amazonaws.com/td-usgs-public/PARQUETDATA/09394500/2018/06/27.parquet ColPosition 1 Name GageHeight2 TdatDataType FLOAT PhysicalType DOUBLE LogicalType NONE Precision 0 Scale 0 MinLength 0 MaxLength 0 NullFound 1 FileType parquet Location /S3/s3.amazonaws.com/td-usgs-public/PARQUETDATA/09394500/2018/06/28.parquet ColPosition 1 [...] ColPosition 4 Name datetime TdatDataType VARCHAR PhysicalType BYTE_ARRAY LogicalType UTF8 Precision 0 Scale 0 MinLength 16 MaxLength 16 NullFound 1 FileType parquet Location /S3/s3.amazonaws.com/td-usgs-public/PARQUETDATA/09394500/2018/06/27.parquet ColPosition 4 Name datetime TdatDataType VARCHAR PhysicalType BYTE_ARRAY LogicalType UTF8 Precision 0 Scale 0 MinLength 16 MaxLength 16 NullFound 1 FileType parquet Location /S3/s3.amazonaws.com/td-usgs-public/PARQUETDATA/09394500/2018/06/28.parquetThe output is displayed vertically for readability.