redis/redis-py · error · ValueError

collect sort_by must contain at least one field

Error message

collect sort_by must contain at least one field

What it means

Raised by the collect reducer when sort_by is provided as an iterable but contains no Asc/Desc entries. Sorting within COLLECT requires at least one field directive; an empty iterable is a no-op the library rejects rather than silently dropping the SORTBY clause.

Source

Thrown at redis/commands/search/reducers.py:253

            if not names or any(not n.strip() for n in names):
                raise ValueError(
                    "collect fields must be '*' or a non-empty list of names"
                )
            names = [_ensure_at_prefix(n) for n in names]
            args += ["FIELDS", str(len(names))] + names

        # DISTINCT (optional)
        if distinct:
            args += ["DISTINCT"]

        # SORTBY (optional)
        if sort_by is not None:
            sort_fields = [sort_by] if isinstance(sort_by, (Asc, Desc)) else sort_by
            sort_args: list[str] = []
            for f in sort_fields:
                sort_args += [_ensure_at_prefix(f.field), f.DIRSTRING]
            if not sort_args:
                raise ValueError("collect sort_by must contain at least one field")
            args += ["SORTBY", str(len(sort_args))] + sort_args

        # LIMIT (optional)
        if limit is not None:
            offset, count = limit
            args += ["LIMIT", str(offset), str(count)]

        super().__init__(*args)

View on GitHub (pinned to da03cdc7e8)

Solutions

1. Pass at least one Asc/Desc instance: from redis.commands.search.aggregation import Asc, Desc; collect(fields='*', sort_by=Asc('price')).
2. If sorting is optional, omit sort_by entirely (pass None) when there is nothing to sort by.
3. Guard dynamic inputs: only pass sort_by when the list is non-empty.

Example fix

// before
collect(fields='*', sort_by=sort_dirs or [])
// after
collect(fields='*', sort_by=sort_dirs if sort_dirs else None)

def safe_sort_by(sort_dirs):
    if not sort_dirs:
        return None
    if isinstance(sort_dirs, (Asc, Desc)):
        return sort_dirs
    return list(sort_dirs) if len(list(sort_dirs)) else None

# usage: collect(fields='*', sort_by=safe_sort_by(dirs))

from redis.commands.search.aggregation import Asc, Desc

def has_sort_entries(sort_by) -> bool:
    if sort_by is None:
        return True
    if isinstance(sort_by, (Asc, Desc)):
        return True
    return len(list(sort_by)) > 0

try:
    collect(fields='*', sort_by=dirs)
except ValueError:
    collect(fields='*', sort_by=None)

When it happens

Trigger: collect(fields='*', sort_by=[]) or collect(fields='*', sort_by=sort_dirs) where sort_dirs is an empty list/generator.

Common situations: Building sort directives dynamically from user choices that resolved to none; unpacking an empty list into sort_by; refactoring that left a default empty list.

Related errors

• collect fields must be '*' or a non-empty list of names
• Did not receive a SortByField.
• index_type must be one of {list(IndexType)}
• prefix must be provided
• Did not receive a Filter object.

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/e177c6e184b3d5ca.json. Report an issue: GitHub.