aux4/db-postgres

PostgreSQL database tools for the aux4 CLI.

The aux4/db-postgres package provides seamless integration with PostgreSQL databases directly from your command line. You can execute SQL queries, perform batch inserts, stream results for large datasets, manage transactions, and handle errors gracefully. Ideal for quick prototypes, ETL pipelines, automation scripts, and interactive database tasks without writing custom scripts.

Installation

aux4 aux4 pkger install aux4/db-postgres

Quick Start

Connect to a database, create a table, insert a record, and query data:

# Create a users table
aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "CREATE TABLE IF NOT EXISTS users (id SERIAL PRIMARY KEY, name TEXT, age INTEGER, email TEXT)"

# Insert a user and return the inserted row as JSON
aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES ('Alice', 30, 'alice@example.com') RETURNING *"

Usage

Main Commands

• aux4 db postgres execute - Execute SQL statements on a PostgreSQL database and return all results as a JSON array.
• aux4 db postgres stream - Execute SQL statements and stream each row as a newline-delimited JSON object.
• aux4 db postgres describe - Describe the columns of a table (types, keys, defaults, and comments) using a stable canonical schema.

Command Reference

aux4 db postgres execute

Run one or more SQL statements on a PostgreSQL database and collect all results in memory.

Usage:

aux4 db postgres execute \
  [--host <hostname>] \
  [--port <port>] \
  [--database <dbname>] \
  [--user <username>] \
  [--password <password>] \
  [--query "<SQL>"] \
  [--file <script.sql>] \
  [--inputStream] \
  [--tx] \
  [--ignore]

Options:

• --host <hostname> Database host (default: localhost)
• --port <port> Database port (default: 5432)
• --database <dbname> Database name (default: postgres)
• --user <username> Database user (default: postgres)
• --password <password> Database password
• --query "<SQL>" SQL statement to execute (positional if arg: true)
• --file <sql_file.sql> Execute SQL from a file
• --inputStream Read a JSON array from stdin as input parameters
• --tx Wrap all operations in a single transaction
• --ignore Ignore errors and continue processing, reporting failures

Examples:

# Named-parameter insert
aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --name Bob --age 25 --email bob@example.com

# Batch insert from JSON via stdin
echo '[{"name":"Carol","age":22,"email":"carol@example.com"}]' | \
  aux4 db postgres execute \
    --host localhost --port 5432 --database mydb --user postgres --password mypass \
    --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
    --inputStream

# Transactional insert (rollback on error)
echo '[{"name":"Tx1","age":40,"email":"tx1@example.com"},{"name":""}]' | \
  aux4 db postgres execute \
    --host localhost --port 5432 --database mydb --user postgres --password mypass \
    --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
    --inputStream --tx

aux4 db postgres stream

Stream query results row-by-row for large datasets or piping into other commands.

Usage:

aux4 db postgres stream \
  [--host <hostname>] \
  [--port <port>] \
  [--database <dbname>] \
  [--user <username>] \
  [--password <password>] \
  [--query "<SQL>"] \
  [--file <script.sql>] \
  [--inputStream] \
  [--tx] \
  [--ignore]

Options are the same as execute, but results are emitted as newline-delimited JSON objects.

Examples:

# Stream all users
aux4 db postgres stream \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "SELECT * FROM users ORDER BY id"

# Stream with a filter parameter
aux4 db postgres stream \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "SELECT name, email FROM users WHERE age >= :minAge ORDER BY name" \
  --minAge 30

# ETL pipeline: stream and immediately insert into audit table
aux4 db postgres stream \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "SELECT id, name FROM users" | \
  aux4 db postgres stream \
    --host localhost --port 5432 --database mydb --user postgres --password mypass \
    --query "INSERT INTO user_audit (user_id, audit_name) VALUES (:id, :name) RETURNING audit_id" \
    --inputStream

Schema Introspection

The introspection commands let you explore a database's structure — ideal for AI agents and scripts that need to discover tables and columns before querying. They reuse the same connection flags as execute (--host, --port, --database, --user, --password).

Namespace: database + schema. PostgreSQL has two levels of namespacing — a server hosts multiple databases, and each database contains multiple schemas. --database selects the database you connect to; the optional --schema flag selects which schema describe and list tables inspect. When --schema is omitted it defaults to the connection's current schema (current_schema(), normally public). The database (from current_database()) and schema values are carried back on every row so an agent can fully qualify an object.

aux4 db postgres describe

Return the columns of a table as a canonical JSON array, one object per column, in definition order.

Usage:

aux4 db postgres describe \
  [--host <hostname>] \
  [--port <port>] \
  [--database <dbname>] \
  [--user <username>] \
  [--password <password>] \
  [--schema <schema>] \
  --table <table_name>

Options:

• --host <hostname> Database host (default: localhost)
• --port <port> Database port (default: 5432)
• --database <dbname> Database name (default: postgres)
• --user <username> Database user (default: postgres)
• --password <password> Database password
• --schema <schema> Schema to inspect (default: current schema, normally public)
• --table <table_name> Name of the table to describe (bound safely as a named parameter)

Example:

aux4 db postgres describe \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --table product

[
  {"name":"id","type":"integer","nullable":false,"key":"PRI","comment":"Unique product identifier"},
  {"name":"name","type":"character varying","nullable":false,"comment":"Product display name"},
  {"name":"price","type":"numeric","nullable":true,"default":"0.00","comment":"Unit price in USD"}
]

Only keys that carry a value are returned — null and empty ("") fields are omitted, so a plain column is just {"name", "type", "nullable"}. nullable is always present. Primary-key columns are flagged with key: "PRI".

aux4 db postgres list tables

List the base tables in the inspected schema. Each row carries the table name, the database and schema it lives in (so an agent can fully qualify it), and the table comment when one is set.

Usage:

aux4 db postgres list tables \
  [--host <hostname>] \
  [--port <port>] \
  [--database <dbname>] \
  [--user <username>] \
  [--password <password>] \
  [--schema <schema>]

Example:

aux4 db postgres list tables \
  --host localhost --port 5432 --database mydb --user postgres --password mypass

[
  {"name":"product","database":"mydb","schema":"public","comment":"Catalog of products for sale"}
]

As with describe, empty/null fields are omitted — a table with no comment is just {"name", "database", "schema"}.

aux4 db postgres list databases

List the databases available on the server — the starting point for an agent that needs to discover a database before drilling into its schemas and tables. Template databases are excluded.

Usage:

aux4 db postgres list databases \
  [--host <hostname>] \
  [--port <port>] \
  [--database <dbname>] \
  [--user <username>] \
  [--password <password>]

Example:

aux4 db postgres list databases \
  --host localhost --port 5432 --user postgres --password mypass

[
  {"name":"mydb"},
  {"name":"postgres"}
]

aux4 db postgres list schemas

List the schemas in the current database — the intermediate namespace between a database and its tables. Use it to discover which schema a --schema filter should target.

Usage:

aux4 db postgres list schemas \
  [--host <hostname>] \
  [--port <port>] \
  [--database <dbname>] \
  [--user <username>] \
  [--password <password>]

Example:

aux4 db postgres list schemas \
  --host localhost --port 5432 --database mydb --user postgres --password mypass

[
  {"name":"information_schema"},
  {"name":"pg_catalog"},
  {"name":"public"}
]

The system schemas (information_schema, pg_catalog, pg_toast) are included; filter them client-side if you only want application schemas.

Canonical Output Schema

Introspection output uses a fixed, dialect-independent set of keys so that tooling works identically across every aux4/db-* adapter. A key is present only when it carries a value — null and empty ("") fields are omitted rather than emitted, keeping the output compact.

describe — one object per column. When present, keys appear in this order:

| Key | Type | Presence | |-----|------|----------| | name | string | always | | type | string | always | | nullable | boolean | always — true if the column accepts NULL, else false | | default | string | only when the column has a default | | key | string | only when set — PRI for primary-key columns | | extra | string | only when set (PostgreSQL rarely emits this) | | comment | string | only when the column has a comment |

list tables — one object per table:

| Key | Type | Presence | |-----|------|----------| | name | string | always | | database | string | always — the database the table lives in | | schema | string | always — the schema (namespace) the table lives in | | comment | string | only when the table has a comment |

Notes:

• nullable is a real JSON boolean (true/false) — never the string "YES"/"NO" and never the number 1/0.
• comment carries the semantic description of the column or table, which is especially useful for AI agents exploring an unfamiliar schema.
• name, type, and nullable are guaranteed on every describe row; everything else is present only when it has a value. This same schema is shared verbatim by the other aux4/db-* adapters (namespace naming follows each dialect: MySQL uses database; PostgreSQL/MSSQL add schema; Oracle uses schema).

Output Formats

Execute Command Output

The execute command returns results as JSON arrays:

Success:

[
  {"id": 1, "name": "Alice", "age": 30, "email": "alice@example.com"},
  {"id": 2, "name": "Bob", "age": 25, "email": "bob@example.com"}
]

Errors (to stderr):

[{"item": {"name": "Bad Data"}, "query": "INSERT INTO users...", "error": "column \"age\" cannot be null"}]

Stream Command Output

The stream command returns newline-delimited JSON objects (NDJSON):

{"id": 1, "name": "Alice", "age": 30, "email": "alice@example.com"}
{"id": 2, "name": "Bob", "age": 25, "email": "bob@example.com"}

Errors (to stderr):

{"item": {}, "query": "SELECT invalid_column FROM users", "error": "column \"invalid_column\" does not exist"}

Advanced Features

Batch Processing with inputStream

Process multiple records from JSON input:

# Create JSON file with batch data
cat > users.json << EOF
[
  {"name": "User1", "age": 25, "email": "user1@example.com"},
  {"name": "User2", "age": 30, "email": "user2@example.com"}
]
EOF

# Execute batch insert
cat users.json | aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --inputStream

Parameter Override

CLI parameters override JSON input parameters:

# Override email for all records in the batch
cat users.json | aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --email "override@example.com" \
  --inputStream

Transaction Management

With transactions (--tx):

• All operations execute within a single transaction
• On error, all changes are rolled back
• Ensures data consistency for batch operations

# Transactional batch - all or nothing
cat batch.json | aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --inputStream --tx

Without transactions:

• Each operation commits individually
• Successful operations persist even if later ones fail
• Faster for large batches but less consistent

Error Handling

Default behavior (--ignore not set):

• Stop on first error
• Exit with non-zero code
• Error details sent to stderr

With --ignore flag:

• Continue processing remaining records
• Output successful results to stdout
• Send errors to stderr but exit with zero code

# Process all records, ignoring failures
cat mixed_data.json | aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --inputStream --ignore

Examples

Basic Query

aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "SELECT * FROM users"

Insert with Named Parameters

aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --name "Dave" --age 45 --email dave@example.com

Query with Parameters

aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "SELECT * FROM users WHERE age >= :minAge AND email LIKE :domain" \
  --minAge 25 --domain "%@example.com"

Transaction Rollback Demonstration

# Good and bad records in a single batch; --tx rolls back all if any fail
echo '[{"name":"Good","age":20,"email":"good@example.com"},{"name":"Bad"}]' | \
  aux4 db postgres execute \
    --host localhost --port 5432 --database mydb --user postgres --password mypass \
    --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
    --inputStream --tx

Stream Processing Pipeline

# Create audit table
aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "CREATE TABLE user_audit (audit_id SERIAL PRIMARY KEY, user_id INTEGER, user_name TEXT, audit_timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP)"

# Stream users and insert audit records
aux4 db postgres stream \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "SELECT id, name FROM users WHERE age >= 25" | \
  aux4 db postgres stream \
    --host localhost --port 5432 --database mydb --user postgres --password mypass \
    --query "INSERT INTO user_audit (user_id, user_name) VALUES (:id, :name) RETURNING audit_id" \
    --inputStream

Error Recovery with --ignore

# Process mixed data, continuing despite errors
cat > mixed_data.json << EOF
[
  {"name": "Valid User", "age": 30, "email": "valid@example.com"},
  {"invalid_field": "bad data"},
  {"name": "Another Valid User", "age": 25, "email": "another@example.com"}
]
EOF

cat mixed_data.json | aux4 db postgres execute \
  --host localhost --port 5432 --database mydb --user postgres --password mypass \
  --query "INSERT INTO users (name, age, email) VALUES (:name, :age, :email) RETURNING *" \
  --inputStream --ignore

License

This package does not specify a license in its manifest. Please refer to the repository or the aux4 hub listing for licensing details.