What causes "Facet are not supported in quickwit yet." in quickwit-oss/quickwit?

Remove the `facet` field mapping and use a regular text/json field with hierarchical values instead.

Facet are not supported in quickwit yet.

Error message

Facet are not supported in quickwit yet.

What it means

When building field mapping entries from an index config, a mapping whose type is `facet` reaches an explicit unimplemented!(): facets are a Tantivy feature Quickwit has not implemented. Unlike `custom` fields (which produce a proper bail! error), facet mappings abort with a panic.

Source

Thrown at quickwit/quickwit-doc-mapper/src/doc_mapper/field_mapping_entry.rs:774

            Ok(FieldMappingType::I64(numeric_options, cardinality))
        }
        Type::F64 => {
            let numeric_options: QuickwitNumericOptions = serde_json::from_value(json)?;
            Ok(FieldMappingType::F64(numeric_options, cardinality))
        }
        Type::Bool => {
            let bool_options: QuickwitBoolOptions = serde_json::from_value(json)?;
            Ok(FieldMappingType::Bool(bool_options, cardinality))
        }
        Type::IpAddr => {
            let ip_addr_options: QuickwitIpAddrOptions = serde_json::from_value(json)?;
            Ok(FieldMappingType::IpAddr(ip_addr_options, cardinality))
        }
        Type::Date => {
            let date_time_options = serde_json::from_value::<QuickwitDateTimeOptions>(json)?;
            Ok(FieldMappingType::DateTime(date_time_options, cardinality))
        }
        Type::Facet => unimplemented!("Facet are not supported in quickwit yet."),
        Type::Custom => bail!("custom fields are not supported in Quickwit"),
        Type::Bytes => {
            let numeric_options: QuickwitBytesOptions = serde_json::from_value(json)?;
            if numeric_options.fast && cardinality == Cardinality::MultiValued {
                bail!("fast field is not allowed for array<bytes>");
            }
            Ok(FieldMappingType::Bytes(numeric_options, cardinality))
        }
        Type::Json => {
            let json_options: QuickwitJsonOptions = serde_json::from_value(json)?;
            Ok(FieldMappingType::Json(json_options, cardinality))
        }
    }
}

impl TryFrom<FieldMappingEntryForSerialization> for FieldMappingEntry {
    type Error = String;

View on GitHub (pinned to a39730c5cd)

Solutions

Remove the `facet` field mapping and use a regular text/json field with hierarchical values instead.
Prefer storing hierarchical paths (e.g. '/a/b/c') in a text field and filtering with prefix queries.
File/upvote upstream support for facets in Quickwit.

Example fix

// before
"category": { "type": "facet" }
// after
"category": { "type": "text", "tokenizer": "raw" }

Defensive patterns

Strategy: validation

Validate before calling

// validate index config before creating the index:
for (_name, entry) in &doc_mapping.field_mappings {
    if entry_type_is(entry, "facet") {
        return Err("facet fields are not supported in Quickwit".into());
    }
}

Try / catch

// replace the unimplemented! with bail! so config errors surface as 400s:
Type::Facet => bail!("facet fields are not supported in quickwit yet"),

Prevention

Never use `type: facet` in Quickwit index configs; it is not a supported mapping type.
Model hierarchical categories as text fields with delimited paths and prefix queries.
Run `quickwit index create` against a validated config schema that rejects facet early.

When it happens

Trigger: Declaring `type: facet` in an index config field_mapping_entries and ingesting/creating the index, hitting Type::Facet in the type-deserialization match.

Common situations: Porting Tantivy-based configs to Quickwit; users copying facet examples from Tantivy docs; migrating configs from other search engines that support facets.

Related errors

AI-assisted analysis of quickwit-oss/quickwit@a39730c5cd (2026-09-08). Data as JSON: /api/errors/b5e41b3bfe456cee. Report an issue: GitHub.