Parquet Import

Import Parquet files into DB9 tables using COPY ... FORMAT parquet from HTTP URLs. No external tools or ETL pipelines are required.

Installation

CREATE EXTENSION parquet;

The read_parquet() table-valued function is not yet available in DB9 CLI 2.2.0. Calling it returns:

ERROR: unknown function: READ_PARQUET (0A000)

Use COPY FROM ... FORMAT parquet to import Parquet data into an existing table instead.

COPY FROM Parquet

Use COPY ... FORMAT parquet to import Parquet data from an HTTP URL into an existing table:

-- Import from HTTP URL
COPY my_table FROM 'https://example.com/export.parquet' FORMAT parquet;

The Parquet file schema must be compatible with the target table. Column names are matched by name (case-insensitive). Extra columns in the Parquet file are ignored.

Type Mapping

Parquet physical types are mapped to PostgreSQL types during COPY FROM:

Parquet Type	PostgreSQL Type
`BOOLEAN`	`BOOLEAN`
`INT32`	`INTEGER`
`INT64`	`BIGINT`
`FLOAT`	`REAL`
`DOUBLE`	`DOUBLE PRECISION`
`BYTE_ARRAY` (UTF8)	`TEXT`
`BYTE_ARRAY` (binary)	`BYTEA`
`INT96` (timestamp)	`TIMESTAMP`
`DATE` logical type	`DATE`
`TIME` logical type	`TIME`
`TIMESTAMP` logical type	`TIMESTAMP`
`DECIMAL` logical type	`NUMERIC`

Limits

Limit	Value
Max Parquet file size	100 MB
Supported Parquet versions	v1, v2
Max columns per file	Unlimited (practical limit: storage)
Remote URL fetch timeout	30 seconds
Supported compression codecs	Snappy, Gzip, Zstd, uncompressed

See Limits and Quotas for the complete list.

Error Messages

Error	Cause
`ERROR: unknown function: READ_PARQUET`	`read_parquet()` is not yet available. Use `COPY FROM` instead.
`parquet: HTTP fetch failed (status 404)`	The remote URL returned a 404. Verify the URL is accessible.
`parquet: HTTP fetch failed (timeout)`	Remote fetch exceeded 30 seconds.
`parquet: invalid magic bytes`	The file is not a valid Parquet file.
`parquet: unsupported encoding`	File uses an unsupported encoding. Re-export with Snappy or Gzip compression.
`parquet: file too large (max 100 MB)`	File exceeds the 100 MB limit. Split into smaller files.
`ERROR: column "x" does not exist`	COPY target table is missing a column present in the Parquet file.
`ERROR: Only http:// and https:// URLs are supported`	fs9 paths are not supported for Parquet COPY. Use an HTTP URL.

Next Steps

HTTP from SQL — Fetch Parquet files from external HTTP endpoints
Extensions Overview — All 9 built-in extensions
Limits and Quotas — All operational limits