Solr Too Many Boolean Clauses Error

The Error

Your search query fails with this exception:

org.apache.solr.common.SolrException: Too many boolean clauses (1025).

This means Solr tried to run a query that expanded into more than 1,024 individual conditions, and hit the safety limit.

What Is Actually Happening

Every search query that Solr processes gets broken down into boolean clauses — individual yes/no conditions that Solr checks against every document. A simple query like q=hello is just 1 clause. But some queries expand into hundreds or thousands of clauses behind the scenes.

Common Causes

1. Synonym Explosion

If your synonyms.txt maps each word to many alternatives, a simple 5-word query can explode into hundreds of clauses. Each synonym adds a new clause for every term.

2. Wildcard Queries

Queries like *term (leading wildcard) or very short prefix queries like a* match thousands of terms in the index. Each matched term becomes a clause.

3. Massive Filter Lists

Sending a filter query with hundreds of values like fq=id:(1 OR 2 OR 3 OR ... OR 2000) creates one clause per value.

How to Fix It

Solution 1: Increase the Limit (Quick Fix)

Important (July 2024 update): The maxBooleanClauses setting has moved to solr.xml (not solrconfig.xml).

Contact Opensolr Support to increase this limit for your Opensolr Index. The setting lives in solr.xml:

<solr>
  <int name="maxBooleanClauses">90589</int>
</solr>

Since solr.xml is a server-level config, you will need to contact support to change it.

Solution 2: Reduce Query Expansion (Root Cause Fix)

• Trim your synonyms.txt — remove rarely used synonyms that expand queries unnecessarily
• Avoid leading wildcards — use term* (prefix) instead of *term (leading wildcard). If you need substring matching, use an n-gram tokenizer instead
• Split large filter lists — break fq=id:(val1 OR val2 OR ... OR val2000) into multiple smaller queries and combine results in your application

Solution 3: Optimize Your Analyzer Chain

• Apply synonyms at query time using SynonymGraphFilterFactory, not at index time — this gives you more control
• Place stopword filters before synonym filters — removing common words first means fewer terms for the synonym filter to expand
• Use edgeNgram tokenizers for partial matching instead of wildcard queries

Quick Reference

Quick Checklist

• Check your synonyms.txt — are there terms with dozens of synonyms?
• Check for wildcard queries — especially leading wildcards (*term)
• Check for large OR lists in filter queries
• Ask Opensolr Support to increase maxBooleanClauses in solr.xml if needed
• Consider using n-gram fields instead of wildcard queries for partial matching

Need your boolean clause limit increased? Reach out to us at support@opensolr.com — we can adjust it for your Opensolr Index in minutes.