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Databases · head to head

Apache Solr vs GNAT Pro

Apache Solr logo

Apache Solr

Databases

Enterprise search platform built on Apache Lucene

From
Free
Free plan
Yes
Visit Apache SolrFull review
GNAT Pro logo

GNAT Pro

Developer Tools

Software development environments and toolchains for Ada, C/C++ and Rust

From
On request
Free plan
No
Visit GNAT ProFull review

The short version

  • Apache Solr is free; GNAT Pro prices on request.
  • Where Apache Solr falls short: XML-heavy configuration and a developer experience that feels dated beside newer engines.
  • Where GNAT Pro falls short: no pricing published on website; requires contacting AdaCore directly for quotes.
  • Prices and features on this page were last checked on 13 November 2026.

Where they differ

Only the attributes on which Apache Solr and GNAT Pro actually diverge.

Attributes where Apache Solr and GNAT Pro differ
AttributeApache SolrGNAT Pro
Starting priceFreeOn request
Pricing modelOpen source, no licence feeQuote
Free tierYesNo
PlatformsLinux, Self-hostedWeb
CategoryDatabasesDeveloper Tools

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Apache Solr

  • Lucene-based indexing
  • Faceted search
  • SolrCloud
  • Schema control

Only in GNAT Pro

Nothing recorded that Apache Solr does not also cover.

What people use each for

The jobs each tool is most often brought in to do.

Apache Solr

  • Library, archive and catalogue search where faceting is centralnot GNAT Pro
  • Long-lived enterprise deployments valuing stability over noveltynot GNAT Pro
  • Search requiring precise, explicitly configured relevance tuningnot GNAT Pro

GNAT Pro

  • Building certified avionics software meeting DO-178B/C standardsnot Apache Solr
  • Developing automotive embedded systems with ISO-26262 compliancenot Apache Solr
  • Integrating Ada, C/C++, and Rust components in single codebasenot Apache Solr
  • Managing software supply chain vulnerabilities and SBOMsnot Apache Solr
  • Supporting long-lived software systems spanning decadesnot Apache Solr

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Apache Solr

  • XML-heavy configuration and a developer experience that feels dated beside newer engines
  • SolrCloud depends on ZooKeeper, adding a component Elasticsearch removed years ago
  • Smaller mindshare now, so newer tutorials, hiring and integrations favour Elasticsearch
  • Considerably heavier than a purpose-built application search engine

GNAT Pro

  • No pricing published on website; requires contacting AdaCore directly for quotes
  • Vendor indicates per-user, per-year subscription model but does not disclose specific costs

Pricing, plan by plan

Apache Solr

Free
  • Apache SolrFree
    • Full functionality
    • No usage limits
    • Community support

GNAT Pro

On request

No published plan breakdown. See the GNAT Pro review.

Which should you pick?

Choose Apache Solr if

  • You need lucene-based indexing.
  • You want to start without paying.
  • You work on Linux, Self-hosted.
  • You also want faceted search.
Apache Solr review

Choose GNAT Pro if

Nothing in the data separates GNAT Pro from Apache Solr on the points above - pick on price and on how each one feels to use.

GNAT Pro review

Questions people ask

Is Apache Solr or GNAT Pro better?
Neither clearly leads. Apache Solr starts at Free and GNAT Pro at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Apache Solr or GNAT Pro?
Apache Solr has a free tier; the other does not. Paid plans start at Free for Apache Solr and On request for GNAT Pro.
Does Apache Solr or GNAT Pro run on more platforms?
Apache Solr runs on Linux, Self-hosted. GNAT Pro runs on Web.
Can I use Apache Solr for free?
Yes. Apache Solr has a free tier, so you can try it without paying. GNAT Pro starts at On request.
What is Apache Solr best used for?
Apache Solr is most often used for library, archive and catalogue search where faceting is central, long-lived enterprise deployments valuing stability over novelty, search requiring precise, explicitly configured relevance tuning. Of those, library, archive and catalogue search where faceting is central and long-lived enterprise deployments valuing stability over novelty are not what GNAT Pro is typically brought in for.
What can Apache Solr do that GNAT Pro cannot?
Apache Solr covers Lucene-based indexing, Faceted search, SolrCloud, Schema control.

Answered from the vendors’ own pages

Apache Solr: Is Apache Solr free?

Yes, open source under the Apache Software Foundation.

GNAT Pro: How much does GNAT Pro cost?

GNAT Pro pricing is not published on the website. Customers must request a pricing quote by contacting AdaCore directly or speaking with a GNAT Pro expert.

Source
Apache Solr: Solr or Elasticsearch?

Both are built on Lucene. Elasticsearch has the larger ecosystem and a friendlier API; Solr is very mature and strong on faceted search, and remains common in library and catalogue systems.

GNAT Pro: What is GNAT Pro licensing model?

GNAT Pro is sold on a per-user, per-year basis with no license locks. Customers can request pricing for their specific needs.

Source
Apache Solr: Is Solr still maintained?

Yes, actively, as a top-level Apache project.

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