Export PostgreSQL table to 10 Parquet files with chDB in 15 lines

export-parquet.py

import chdb

# Get total rows
total_rows = int(chdb.query("""
    SELECT COUNT(*) 
    FROM postgresql('192.168.3.135', 'sample_db', 'users', 'postgres', 'mysecretpassword')
""").bytes().strip())

# Calculate rows per file
rows_per_file = -(-total_rows // 10)  # Ceiling division

# Export to 10 files
for i in range(10):
    chdb.query(f"""
        SELECT *
        FROM postgresql('192.168.3.135', 'sample_db', 'users', 'postgres', 'mysecretpassword')
        WHERE rowNumberInAllBlocks() > {i * rows_per_file} 
        AND rowNumberInAllBlocks() <= {(i + 1) * rows_per_file}
        INTO OUTFILE 'users_part_{i+1}.parquet'
    """)
    print(f"Exported part {i+1}/10")

out.txt

Exported part 1/10
Exported part 2/10
Exported part 3/10
Exported part 4/10
Exported part 5/10
Exported part 6/10
Exported part 7/10
Exported part 8/10
Exported part 9/10
Exported part 10/10

# ls -l
-rw-r--r--  1 root root        1589 Nov 14 07:21 users_part_1.parquet
-rw-r--r--  1 root root        1577 Nov 14 07:21 users_part_10.parquet
-rw-r--r--  1 root root        1592 Nov 14 07:21 users_part_2.parquet
-rw-r--r--  1 root root        1592 Nov 14 07:21 users_part_3.parquet
-rw-r--r--  1 root root        1588 Nov 14 07:21 users_part_4.parquet
-rw-r--r--  1 root root        1588 Nov 14 07:21 users_part_5.parquet
-rw-r--r--  1 root root        1592 Nov 14 07:21 users_part_6.parquet
-rw-r--r--  1 root root        1592 Nov 14 07:21 users_part_7.parquet
-rw-r--r--  1 root root        1592 Nov 14 07:21 users_part_8.parquet
-rw-r--r--  1 root root        1582 Nov 14 07:21 users_part_9.parquet

setup-pg.sh

# Create a Docker container running PostgreSQL
docker run --name my-postgres \
  -e POSTGRES_PASSWORD=mysecretpassword \
  -e POSTGRES_DB=sample_db \
  -p 5432:5432 \
  -d postgres:latest

# Wait a few seconds for the container to start
sleep 5

# Create a SQL file with table creation and sample data
cat << 'EOF' > init.sql
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50),
    email VARCHAR(100),
    age INT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

INSERT INTO users (name, email, age)
SELECT 
    'User ' || generate_series AS name,
    'user' || generate_series || '@example.com' AS email,
    (random() * 50 + 20)::int AS age
FROM generate_series(1, 100);
EOF

# Execute the SQL file
docker exec -i my-postgres psql -U postgres -d sample_db < init.sql

You can try use more parts to export