What is PISA used for?

PISA is a C++ text search engine and toolkit for researchers to experiment with index compression, query processing and document reordering on large collections. It is a good fit for information retrieval research experiments, benchmarking index compression techniques and teaching how search engines work.

Yes. PISA is open source under the Apache-2.0 licence. Its source code is on GitHub at pisa-engine/pisa and is written mainly in C++.

Yes. PISA is open source, so the software itself is free to use.

What are some alternatives to PISA?

Similar open-source tools in the Search category include OpenSSE, Typesense and ZincSearch. SaaS products in the same category include Baidu, Bing and Brave Search.

Is PISA actively maintained?

Yes. The most recent commit to PISA was on 20 September 2026, and the latest release is v0.10.0, published on 9 December 2024. The project has 1.1k stars on GitHub.

PISA: open-source search

About PISA

PISA, short for Performant Indexes and Search for Academia, is a text search engine that can run on large-scale document collections. It is aimed at researchers who want to experiment with state-of-the-art indexing and query processing techniques in an environment designed for rapid development.

Given a text collection, PISA builds an inverted index, which stores a list of documents for each term, and then searches it, with the index held in main memory at query time. It supports Boolean AND and OR queries and ranked retrieval, and offers parsing, indexing and sharding, many index compression methods, many query processing algorithms and document reordering. Documentation is published as an online book.

PISA is written in C++ for performance, licensed under the permissive Apache-2.0 licence, and has a community Slack workspace. It is built and run locally, so it is a research toolkit rather than a hosted service. It suits information retrieval researchers and students who want to benchmark or study indexing techniques.

Key features

Inverted index construction
Many index compression methods
Many query processing algorithms
Document reordering
Parsing, indexing, and sharding tools
Documentation published as a book

Good fit for

→Information retrieval research experiments
→Benchmarking index compression techniques
→Teaching how search engines work

Built with: C++
Tags: search-engine; inverted-index; information-retrieval; cpp; research; indexing; query-processing; academic

PISA: questions and answers

What is PISA used for?: PISA is a C++ text search engine and toolkit for researchers to experiment with index compression, query processing and document reordering on large collections. It is a good fit for information retrieval research experiments, benchmarking index compression techniques and teaching how search engines work.
Is PISA open source?: Yes. PISA is open source under the Apache-2.0 licence. Its source code is on GitHub at pisa-engine/pisa and is written mainly in C++.
Is PISA free?: Yes. PISA is open source, so the software itself is free to use.
What are some alternatives to PISA?: Similar open-source tools in the Search category include OpenSSE, Typesense and ZincSearch. SaaS products in the same category include Baidu, Bing and Brave Search.
Is PISA actively maintained?: Yes. The most recent commit to PISA was on 20 September 2026, and the latest release is v0.10.0, published on 9 December 2024. The project has 1.1k stars on GitHub.