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Extension descriptor (YAML)

Automatic query privatization using the PAC Privacy framework

Compatibility Matrix

This table covers all DuckDB releases that have not reached end-of-life, including LTS releases, and shows the 2 most recent patch releases of each. Older patch releases are not listed, but the extension may be available for them as well.

Installing and Loading

INSTALL pac FROM community;
LOAD pac;

Example

-- Generate TPC-H benchmark data
INSTALL tpch;
LOAD tpch;
CALL dbgen(sf=1);

-- Mark customer as the privacy unit
ALTER TABLE customer ADD PAC_KEY (c_custkey);
ALTER TABLE customer SET PU;

-- Protect sensitive customer columns
ALTER PU TABLE customer ADD PROTECTED (c_custkey);
ALTER PU TABLE customer ADD PROTECTED (c_name);
ALTER PU TABLE customer ADD PROTECTED (c_address);
ALTER PU TABLE customer ADD PROTECTED (c_acctbal);

-- Define join chain: lineitem -> orders -> customer
ALTER TABLE orders ADD PAC_LINK (o_custkey) REFERENCES customer(c_custkey);
ALTER TABLE lineitem ADD PAC_LINK (l_orderkey) REFERENCES orders(o_orderkey);

-- Aggregates on linked tables are automatically noised
SELECT l_returnflag, l_linestatus, SUM(l_extendedprice)
FROM lineitem GROUP BY ALL;

About pac

PAC (Probably Approximately Correct) is a DuckDB extension that automatically privatizes SQL queries, protecting against Membership Inference Attacks by adding calibrated noise to aggregate results. Unlike Differential Privacy, PAC works transparently — no per-query privacy analysis by a specialist is needed.

How It Works:

1. Declare a privacy unit table with CREATE PU TABLE or ALTER TABLE SET PU, specifying a PAC_KEY (unique identifier) and PROTECTED columns
2. Protected columns cannot be projected directly — they can only appear inside aggregates
3. The extension automatically rewrites query plans to inject calibrated noise
4. Join chains propagate privacy via PAC_LINK foreign key declarations

Supported Aggregates: SUM, COUNT, AVG, MIN, MAX, COUNT(DISTINCT)

Key Settings:

• pac_mi — Mutual information bound controlling the privacy-utility tradeoff (default: 1/128). Lower values = more noise = more privacy. Set to 0 for deterministic (no noise) mode.
• pac_seed — RNG seed for reproducible noised results

Privacy Propagation: PAC automatically follows foreign key chains declared with PAC_LINK to find the privacy unit. For example, querying lineitem with a link chain lineitem -> orders -> customer will automatically join back to customer to hash the privacy unit key, without any changes to your query.

More information: See the PAC repository for full documentation, examples, and benchmarks.

Requirements:

• DuckDB 1.5.0+

Added Functions

Overloaded Functions

This extension does not add any function overloads.

Added Types

This extension does not add any types.

Added Settings