Added support for searching large amount of indices (#412)

**Description:**
When searching the catalog with the `/search`-endpoint, a `GET
/<indices>/_search` request is done with all indices listed in the URL
path. However when doing such a search on a large amount of indices, it
is possible that the size of the endpoint exceeds Elasticsearch’s
maximum allowed HTTP line length (4096 bytes), resulting in the
following error:

`{"code":"RequestError","description":"RequestError(400,
'too_long_http_line_exception', 'An HTTP line is larger than 4096
bytes.')"}`

The solution in this commit moves the indices from the endpoint to the
body of the request once the amount of indices passes a certain
threshold. The indices of the endpoint will be replaced by
`ITEM_INDICES`. Since the query still filters on the correct indices,
this change preserves the behavior while avoiding the URL length
limitation.

**PR Checklist:**

- [x] Code is formatted and linted (run `pre-commit run --all-files`)
- [x] Tests pass (run `make test`)
- [ ] Documentation has been updated to reflect changes, if applicable
- [x] Changes are added to the changelog

---------

Co-authored-by: Stijn Caerts <stijn.caerts@vito.be>

Author: simonvb00

CHANGELOG.md

@@ -12,6 +12,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Added the ability to set timeout for Opensearch and Elasticsearch clients by setting the environmental variable `ES_TIMEOUT` [#408](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/408)
 
+### Changed
+
+- Updated collection to index logic to support searching a large amount of indices [#412](https://github.com/stac-utils/stac-fastapi-elasticsearch-opensearch/pull/412)
+
 ## [v6.0.0] - 2025-06-22
 
 ### Added

stac_fastapi/elasticsearch/stac_fastapi/elasticsearch/database_logic.py

@@ -43,6 +43,10 @@
     return_date,
     validate_refresh,
 )
+from stac_fastapi.sfeos_helpers.database.query import (
+    ES_MAX_URL_LENGTH,
+    add_collections_to_body,
+)
 from stac_fastapi.sfeos_helpers.database.utils import (
     merge_to_operations,
     operations_to_script,
@@ -520,6 +524,9 @@ async def execute_search(
         query = search.query.to_dict() if search.query else None
 
         index_param = indices(collection_ids)
+        if len(index_param) > ES_MAX_URL_LENGTH - 300:
+            index_param = ITEM_INDICES
+            query = add_collections_to_body(collection_ids, query)
 
         max_result_window = MAX_LIMIT
 

stac_fastapi/opensearch/stac_fastapi/opensearch/database_logic.py

@@ -42,6 +42,10 @@
     return_date,
     validate_refresh,
 )
+from stac_fastapi.sfeos_helpers.database.query import (
+    ES_MAX_URL_LENGTH,
+    add_collections_to_body,
+)
 from stac_fastapi.sfeos_helpers.database.utils import (
     merge_to_operations,
     operations_to_script,
@@ -532,6 +536,12 @@ async def execute_search(
         """
         search_body: Dict[str, Any] = {}
         query = search.query.to_dict() if search.query else None
+
+        index_param = indices(collection_ids)
+        if len(index_param) > ES_MAX_URL_LENGTH - 300:
+            index_param = ITEM_INDICES
+            query = add_collections_to_body(collection_ids, query)
+
         if query:
             search_body["query"] = query
 
@@ -544,8 +554,6 @@ async def execute_search(
 
         search_body["sort"] = sort if sort else DEFAULT_SORT
 
-        index_param = indices(collection_ids)
-
         max_result_window = MAX_LIMIT
 
         size_limit = min(limit + 1, max_result_window)

stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/database/query.py

@@ -7,6 +7,8 @@
 
 from stac_fastapi.sfeos_helpers.mappings import Geometry
 
+ES_MAX_URL_LENGTH = 4096
+
 
 def apply_free_text_filter_shared(
     search: Any, free_text_queries: Optional[List[str]]
@@ -83,3 +85,33 @@ def populate_sort_shared(sortby: List) -> Optional[Dict[str, Dict[str, str]]]:
         return {s.field: {"order": s.direction} for s in sortby}
     else:
         return None
+
+
+def add_collections_to_body(
+    collection_ids: List[str], query: Optional[Dict[str, Any]]
+) -> Dict[str, Any]:
+    """Add a list of collection ids to the body of a query.
+
+    Args:
+        collection_ids (List[str]): A list of collections ids.
+        query (Optional[Dict[str, Any]]): The query to add collections to. If none, create a query that filters
+        the collection ids.
+
+    Returns:
+        Dict[str, Any]: A query that contains a filter on the given collection ids.
+
+    Notes:
+        This function is needed in the execute_search function when the size of the URL path will exceed the maximum of ES.
+    """
+    index_filter = {"terms": {"collection": collection_ids}}
+    if query is None:
+        query = {"query": {}}
+    if "bool" not in query:
+        query["bool"] = {}
+    if "filter" not in query["bool"]:
+        query["bool"]["filter"] = []
+
+    filters = query["bool"]["filter"]
+    if index_filter not in filters:
+        filters.append(index_filter)
+    return query