diff --git a/quickwit/quickwit-config/src/index_config/mod.rs b/quickwit/quickwit-config/src/index_config/mod.rs
index c258c8052d8..b4c6b69d7b1 100644
--- a/quickwit/quickwit-config/src/index_config/mod.rs
+++ b/quickwit/quickwit-config/src/index_config/mod.rs
@@ -14,6 +14,7 @@
 
 pub(crate) mod serialize;
 
+use std::collections::HashSet;
 use std::hash::{Hash, Hasher};
 use std::num::NonZeroUsize;
 use std::str::FromStr;
@@ -565,11 +566,67 @@ pub(super) fn validate_index_config(
     Ok(())
 }
 
+/// Returns the updated doc mapping and a boolean indicating whether a mutation occurred.
+///
+/// The logic goes as follows:
+/// 1. If the new doc mapping is the same as the current doc mapping, ignoring their UIDs, returns
+///    the current doc mapping and `false`, indicating that no mutation occurred.
+/// 2. If the new doc mapping is different from the current doc mapping, verifies the following
+///    constraints before returning the new doc mapping and `true`, indicating that a mutation
+///    occurred:
+///    - The doc mapping UID should differ from the current one
+///    - The timestamp field should remain the same
+///    - The tokenizers should be a superset of the current tokenizers
+///    - A doc mapper can be built from the new doc mapping
+pub fn prepare_doc_mapping_update(
+    mut new_doc_mapping: DocMapping,
+    current_doc_mapping: &DocMapping,
+    search_settings: &SearchSettings,
+) -> anyhow::Result<(DocMapping, bool)> {
+    // Save the new doc mapping UID in a temporary variable and override it with the current doc
+    // mapping UID to compare the two doc mappings, ignoring their UIDs.
+    let new_doc_mapping_uid = new_doc_mapping.doc_mapping_uid;
+    new_doc_mapping.doc_mapping_uid = current_doc_mapping.doc_mapping_uid;
+
+    if new_doc_mapping == *current_doc_mapping {
+        return Ok((new_doc_mapping, false));
+    }
+    // Restore the new doc mapping UID.
+    new_doc_mapping.doc_mapping_uid = new_doc_mapping_uid;
+
+    ensure!(
+        new_doc_mapping.doc_mapping_uid != current_doc_mapping.doc_mapping_uid,
+        "new doc mapping UID should differ from the current one, current UID `{}`, new UID `{}`",
+        current_doc_mapping.doc_mapping_uid,
+        new_doc_mapping.doc_mapping_uid,
+    );
+    let new_timestamp_field = new_doc_mapping.timestamp_field.as_deref();
+    let current_timestamp_field = current_doc_mapping.timestamp_field.as_deref();
+    ensure!(
+        new_timestamp_field == current_timestamp_field,
+        "updating timestamp field is not allowed, current timestamp field `{}`, new timestamp \
+         field `{}`",
+        current_timestamp_field.unwrap_or("none"),
+        new_timestamp_field.unwrap_or("none"),
+    );
+    // TODO: Unsure this constraint is required, should we relax it?
+    let new_tokenizers: HashSet<_> = new_doc_mapping.tokenizers.iter().collect();
+    let current_tokenizers: HashSet<_> = current_doc_mapping.tokenizers.iter().collect();
+    ensure!(
+        new_tokenizers.is_superset(&current_tokenizers),
+        "updating tokenizers is allowed only if adding new tokenizers, current tokenizers \
+         `{current_tokenizers:?}`, new tokenizers `{new_tokenizers:?}`",
+    );
+    build_doc_mapper(&new_doc_mapping, search_settings).context("invalid doc mapping")?;
+    Ok((new_doc_mapping, true))
+}
+
 #[cfg(test)]
 mod tests {
 
     use cron::TimeUnitSpec;
-    use quickwit_doc_mapper::ModeType;
+    use quickwit_doc_mapper::{Mode, ModeType, TokenizerEntry};
+    use quickwit_proto::types::DocMappingUid;
 
     use super::*;
     use crate::ConfigFormat;
@@ -981,4 +1038,96 @@ mod tests {
         let error = serde_yaml::from_str::<IngestSettings>(settings_yaml).unwrap_err();
         assert!(error.to_string().contains("expected a nonzero"));
     }
+
+    #[test]
+    fn test_prepare_doc_mapping_update() {
+        let current_index_config = IndexConfig::for_test("test-index", "s3://test-index");
+        let mut current_doc_mapping = current_index_config.doc_mapping;
+        let search_settings = current_index_config.search_settings;
+
+        let tokenizer_json = r#"
+            {
+                "name": "breton-tokenizer",
+                "type": "regex",
+                "pattern": "crêpes*"
+            }
+            "#;
+        let tokenizer: TokenizerEntry = serde_json::from_str(tokenizer_json).unwrap();
+
+        current_doc_mapping.tokenizers.push(tokenizer.clone());
+
+        // The new doc mapping should have a different doc mapping UID.
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        new_doc_mapping.store_source = false; // This is set to `true` for the current doc mapping.
+        let error =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap_err()
+                .to_string();
+        assert!(error.contains("doc mapping UID should differ"));
+
+        // The new doc mapping should not change the timestamp field.
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        new_doc_mapping.doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.timestamp_field = Some("ts".to_string()); // This is set to `timestamp` for the current doc mapping.
+        let error =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap_err()
+                .to_string();
+        assert!(error.contains("timestamp field"));
+
+        // The new doc mapping should not remove the timestamp field.
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        new_doc_mapping.doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.timestamp_field = None;
+        let error =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap_err()
+                .to_string();
+        assert!(error.contains("timestamp field"));
+
+        // The new doc mapping should not remove tokenizers.
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        new_doc_mapping.doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.tokenizers.clear();
+        let error =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap_err()
+                .to_string();
+        assert!(error.contains("tokenizers"));
+
+        // The new doc mapping should be "buildable" into a doc mapper.
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        new_doc_mapping.doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.tokenizers.push(tokenizer);
+        let error =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap_err()
+                .source()
+                .unwrap()
+                .to_string();
+        assert!(error.contains("duplicated custom tokenizer"));
+
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        new_doc_mapping.doc_mapping_uid = DocMappingUid::random();
+        let (updated_doc_mapping, mutation_occurred) =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap();
+        assert!(!mutation_occurred);
+        assert_eq!(
+            updated_doc_mapping.doc_mapping_uid,
+            current_doc_mapping.doc_mapping_uid
+        );
+        assert_eq!(updated_doc_mapping, current_doc_mapping);
+
+        let mut new_doc_mapping = current_doc_mapping.clone();
+        let new_doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.doc_mapping_uid = new_doc_mapping_uid;
+        new_doc_mapping.mode = Mode::Strict;
+        let (updated_doc_mapping, mutation_occurred) =
+            prepare_doc_mapping_update(new_doc_mapping, &current_doc_mapping, &search_settings)
+                .unwrap();
+        assert!(mutation_occurred);
+        assert_eq!(updated_doc_mapping.doc_mapping_uid, new_doc_mapping_uid);
+        assert_eq!(updated_doc_mapping.mode, Mode::Strict);
+    }
 }
diff --git a/quickwit/quickwit-config/src/index_config/serialize.rs b/quickwit/quickwit-config/src/index_config/serialize.rs
index 5e04e8dbf3c..24fcc6d1ac2 100644
--- a/quickwit/quickwit-config/src/index_config/serialize.rs
+++ b/quickwit/quickwit-config/src/index_config/serialize.rs
@@ -12,11 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use std::collections::HashSet;
-
 use anyhow::{Context, ensure};
 use quickwit_common::uri::Uri;
-use quickwit_doc_mapper::DocMapperBuilder;
 use quickwit_proto::types::{DocMappingUid, IndexId};
 use serde::{Deserialize, Serialize};
 use tracing::info;
@@ -24,7 +21,7 @@ use tracing::info;
 use super::{IngestSettings, validate_index_config};
 use crate::{
     ConfigFormat, DocMapping, IndexConfig, IndexingSettings, RetentionPolicy, SearchSettings,
-    validate_identifier,
+    prepare_doc_mapping_update, validate_identifier,
 };
 
 /// Alias for the latest serialization format.
@@ -92,63 +89,12 @@ pub fn load_index_config_update(
         current_index_config.index_uri,
         new_index_config.index_uri
     );
-
-    // verify the new mapping is coherent
-    let doc_mapper_builder = DocMapperBuilder {
-        doc_mapping: new_index_config.doc_mapping.clone(),
-        default_search_fields: new_index_config
-            .search_settings
-            .default_search_fields
-            .clone(),
-        legacy_type_tag: None,
-    };
-    doc_mapper_builder
-        .try_build()
-        .context("invalid mapping update")?;
-
-    {
-        let new_mapping_uid = new_index_config.doc_mapping.doc_mapping_uid;
-        // we verify whether they are equal ignoring the mapping uid as it is generated at random:
-        // we don't want to record a mapping change when nothing really happened.
-        new_index_config.doc_mapping.doc_mapping_uid =
-            current_index_config.doc_mapping.doc_mapping_uid;
-        if new_index_config.doc_mapping != current_index_config.doc_mapping {
-            new_index_config.doc_mapping.doc_mapping_uid = new_mapping_uid;
-            ensure!(
-                current_index_config.doc_mapping.doc_mapping_uid
-                    != new_index_config.doc_mapping.doc_mapping_uid,
-                "`doc_mapping_doc_mapping_uid` must change when the doc mapping is updated",
-            );
-            ensure!(
-                current_index_config.doc_mapping.timestamp_field
-                    == new_index_config.doc_mapping.timestamp_field,
-                "`doc_mapping.timestamp_field` cannot be updated, current value {}, new expected \
-                 value {}",
-                current_index_config
-                    .doc_mapping
-                    .timestamp_field
-                    .as_deref()
-                    .unwrap_or("<none>"),
-                new_index_config
-                    .doc_mapping
-                    .timestamp_field
-                    .as_deref()
-                    .unwrap_or("<none>"),
-            );
-            // TODO: i'm not sure this is necessary, we can relax this requirement once we know
-            // for sure
-            let current_tokenizers: HashSet<_> =
-                current_index_config.doc_mapping.tokenizers.iter().collect();
-            let new_tokenizers: HashSet<_> =
-                new_index_config.doc_mapping.tokenizers.iter().collect();
-            ensure!(
-                new_tokenizers.is_superset(&current_tokenizers),
-                "`.doc_mapping.tokenizers` must be a superset of previously available tokenizers"
-            );
-        } else {
-            // the docmapping is unchanged, keep the old uid
-        }
-    }
+    let (updated_doc_mapping, _mutation_occurred) = prepare_doc_mapping_update(
+        new_index_config.doc_mapping,
+        &current_index_config.doc_mapping,
+        &new_index_config.search_settings,
+    )?;
+    new_index_config.doc_mapping = updated_doc_mapping;
 
     Ok(new_index_config)
 }
diff --git a/quickwit/quickwit-config/src/lib.rs b/quickwit/quickwit-config/src/lib.rs
index f7589995f5d..21ef6455eed 100644
--- a/quickwit/quickwit-config/src/lib.rs
+++ b/quickwit/quickwit-config/src/lib.rs
@@ -47,6 +47,7 @@ use index_config::serialize::{IndexConfigV0_8, VersionedIndexConfig};
 pub use index_config::{
     IndexConfig, IndexingResources, IndexingSettings, IngestSettings, RetentionPolicy,
     SearchSettings, build_doc_mapper, load_index_config_from_user_config, load_index_config_update,
+    prepare_doc_mapping_update,
 };
 pub use quickwit_doc_mapper::DocMapping;
 use serde::Serialize;
diff --git a/quickwit/quickwit-doc-mapper/src/doc_mapping.rs b/quickwit/quickwit-doc-mapper/src/doc_mapping.rs
index 984932c9a5b..2fae5d45452 100644
--- a/quickwit/quickwit-doc-mapper/src/doc_mapping.rs
+++ b/quickwit/quickwit-doc-mapper/src/doc_mapping.rs
@@ -166,20 +166,6 @@ impl DocMapping {
     pub fn default_max_num_partitions() -> NonZeroU32 {
         NonZeroU32::new(200).unwrap()
     }
-
-    /// Returns whether the `other` doc mapping is equal to `self` leaving their respective doc
-    /// mapping UIDs out of the comparison.
-    pub fn eq_ignore_doc_mapping_uid(&self, other: &Self) -> bool {
-        let doc_mapping_uid = DocMappingUid::default();
-
-        let mut left = self.clone();
-        left.doc_mapping_uid = doc_mapping_uid;
-
-        let mut right = other.clone();
-        right.doc_mapping_uid = doc_mapping_uid;
-
-        left == right
-    }
 }
 
 #[cfg(test)]
diff --git a/quickwit/quickwit-metastore/src/metastore/file_backed/file_backed_index/mod.rs b/quickwit/quickwit-metastore/src/metastore/file_backed/file_backed_index/mod.rs
index 4bc0d19c793..15aeeb21a5c 100644
--- a/quickwit/quickwit-metastore/src/metastore/file_backed/file_backed_index/mod.rs
+++ b/quickwit/quickwit-metastore/src/metastore/file_backed/file_backed_index/mod.rs
@@ -221,7 +221,7 @@ impl FileBackedIndex {
         ingest_settings: IngestSettings,
         search_settings: SearchSettings,
         retention_policy_opt: Option<RetentionPolicy>,
-    ) -> bool {
+    ) -> MetastoreResult<bool> {
         self.metadata.update_index_config(
             doc_mapping,
             indexing_settings,
diff --git a/quickwit/quickwit-metastore/src/metastore/file_backed/mod.rs b/quickwit/quickwit-metastore/src/metastore/file_backed/mod.rs
index 374e1430d81..6c2ecbc196f 100644
--- a/quickwit/quickwit-metastore/src/metastore/file_backed/mod.rs
+++ b/quickwit/quickwit-metastore/src/metastore/file_backed/mod.rs
@@ -575,7 +575,7 @@ impl MetastoreService for FileBackedMetastore {
                     ingest_settings,
                     search_settings,
                     retention_policy_opt,
-                );
+                )?;
                 let index_metadata = index.metadata().clone();
 
                 if mutation_occurred {
diff --git a/quickwit/quickwit-metastore/src/metastore/index_metadata/mod.rs b/quickwit/quickwit-metastore/src/metastore/index_metadata/mod.rs
index 4e40b0dfcda..e7a5677099e 100644
--- a/quickwit/quickwit-metastore/src/metastore/index_metadata/mod.rs
+++ b/quickwit/quickwit-metastore/src/metastore/index_metadata/mod.rs
@@ -20,7 +20,7 @@ use std::collections::hash_map::Entry;
 use quickwit_common::uri::Uri;
 use quickwit_config::{
     DocMapping, IndexConfig, IndexingSettings, IngestSettings, RetentionPolicy, SearchSettings,
-    SourceConfig,
+    SourceConfig, prepare_doc_mapping_update,
 };
 use quickwit_proto::metastore::{EntityKind, MetastoreError, MetastoreResult};
 use quickwit_proto::types::{IndexUid, SourceId};
@@ -106,13 +106,16 @@ impl IndexMetadata {
         ingest_settings: IngestSettings,
         search_settings: SearchSettings,
         retention_policy_opt: Option<RetentionPolicy>,
-    ) -> bool {
-        let mut mutation_occurred = false;
-
-        if doc_mapping != self.index_config.doc_mapping {
-            self.index_config.doc_mapping = doc_mapping;
-            mutation_occurred = true;
-        }
+    ) -> MetastoreResult<bool> {
+        let (updated_doc_mapping, mut mutation_occurred) = prepare_doc_mapping_update(
+            doc_mapping,
+            &self.index_config.doc_mapping,
+            &search_settings,
+        )
+        .map_err(|error| MetastoreError::InvalidArgument {
+            message: error.to_string(),
+        })?;
+        self.index_config.doc_mapping = updated_doc_mapping;
         if indexing_settings != self.index_config.indexing_settings {
             self.index_config.indexing_settings = indexing_settings;
             mutation_occurred = true;
@@ -129,7 +132,7 @@ impl IndexMetadata {
             self.index_config.retention_policy_opt = retention_policy_opt;
             mutation_occurred = true;
         }
-        mutation_occurred
+        Ok(mutation_occurred)
     }
 
     /// Adds a source to the index. Returns an error if the source already exists.
@@ -234,3 +237,96 @@ impl quickwit_config::TestableForRegression for IndexMetadata {
         assert_eq!(self.sources, other.sources);
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use quickwit_doc_mapper::Mode;
+    use quickwit_proto::types::DocMappingUid;
+
+    use super::*;
+
+    #[test]
+    fn test_update_index_config() {
+        let current_index_config = IndexConfig::for_test("test-index", "s3://test-index");
+        let mut current_index_metadata = IndexMetadata::new(current_index_config.clone());
+
+        let mutation_occurred = current_index_metadata
+            .update_index_config(
+                current_index_config.doc_mapping.clone(),
+                current_index_config.indexing_settings.clone(),
+                current_index_config.ingest_settings.clone(),
+                current_index_config.search_settings.clone(),
+                current_index_config.retention_policy_opt.clone(),
+            )
+            .unwrap();
+        assert!(!mutation_occurred);
+
+        let new_search_settings = SearchSettings {
+            default_search_fields: vec!["message".to_string(), "status".to_string()],
+        };
+        let mutation_occurred = current_index_metadata
+            .update_index_config(
+                current_index_config.doc_mapping.clone(),
+                current_index_config.indexing_settings.clone(),
+                current_index_config.ingest_settings.clone(),
+                new_search_settings,
+                current_index_config.retention_policy_opt.clone(),
+            )
+            .unwrap();
+        assert!(mutation_occurred);
+        assert_eq!(
+            current_index_metadata
+                .index_config()
+                .search_settings
+                .default_search_fields,
+            ["message", "status"]
+        );
+    }
+
+    #[test]
+    fn test_update_doc_mapping() {
+        let current_index_config = IndexConfig::for_test("test-index", "s3://test-index");
+        let mut current_index_metadata = IndexMetadata::new(current_index_config.clone());
+
+        let mut new_doc_mapping = current_index_config.doc_mapping.clone();
+        new_doc_mapping.doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.timestamp_field = Some("ts".to_string()); // This is set to `timestamp` for the current doc mapping.
+
+        current_index_metadata
+            .update_index_config(
+                new_doc_mapping,
+                current_index_config.indexing_settings.clone(),
+                current_index_config.ingest_settings.clone(),
+                current_index_config.search_settings.clone(),
+                current_index_config.retention_policy_opt.clone(),
+            )
+            .unwrap_err();
+
+        let mut new_doc_mapping = current_index_config.doc_mapping.clone();
+        let new_doc_mapping_uid = DocMappingUid::random();
+        new_doc_mapping.doc_mapping_uid = new_doc_mapping_uid;
+        new_doc_mapping.mode = Mode::Strict;
+
+        let mutation_occurred = current_index_metadata
+            .update_index_config(
+                new_doc_mapping,
+                current_index_config.indexing_settings,
+                current_index_config.ingest_settings,
+                current_index_config.search_settings,
+                current_index_config.retention_policy_opt,
+            )
+            .unwrap();
+        assert!(mutation_occurred);
+        assert_eq!(
+            current_index_metadata
+                .index_config()
+                .doc_mapping
+                .doc_mapping_uid,
+            new_doc_mapping_uid
+        );
+        assert_eq!(
+            current_index_metadata.index_config().doc_mapping.mode,
+            Mode::Strict
+        );
+    }
+}
diff --git a/quickwit/quickwit-metastore/src/metastore/postgres/metastore.rs b/quickwit/quickwit-metastore/src/metastore/postgres/metastore.rs
index e4a00285df0..e63a9400688 100644
--- a/quickwit/quickwit-metastore/src/metastore/postgres/metastore.rs
+++ b/quickwit/quickwit-metastore/src/metastore/postgres/metastore.rs
@@ -431,7 +431,7 @@ impl MetastoreService for PostgresqlMetastore {
                     ingest_settings,
                     search_settings,
                     retention_policy_opt,
-                );
+                )?;
                 Ok(MutationOccurred::from(mutation_occurred))
             })
             .await