redis: got %d elements in the VSIM array, wanted a multiple

Error message

redis: got %d elements in the VSIM array, wanted a multiple of 2

What it means

VSIM replies parsed into VectorAttrib values must be name/attribute pairs, so the top-level array length must be a multiple of 2. An odd count means the reply does not contain the expected pairs and parsing stops before allocating the result slice.

Source

Thrown at command.go:8825

			name, err := rd.ReadString()
			if err != nil {
				return err
			}
			attrib, err := readVectorAttribStringOrNil(rd)
			if err != nil {
				return err
			}
			cmd.val[i] = VectorAttrib{Name: name, Attribs: attrib}
		}
		return nil
	}

	n, err := rd.ReadArrayLen()
	if err != nil {
		return err
	}
	if n%2 != 0 {
		return fmt.Errorf("redis: got %d elements in the VSIM array, wanted a multiple of 2", n)
	}
	cmd.val = make([]VectorAttrib, n/2)
	for i := range cmd.val {
		name, err := rd.ReadString()
		if err != nil {
			return err
		}
		attrib, err := readVectorAttribStringOrNil(rd)
		if err != nil {
			return err
		}
		cmd.val[i] = VectorAttrib{Name: name, Attribs: attrib}
	}
	return nil
}

func (cmd *VectorAttribSliceCmd) Clone() Cmder {
	return &VectorAttribSliceCmd{

View on GitHub (pinned to c5cad058c7)

Solutions

Ensure you use the command variant whose option flags match the parser (WITHATTRIBS only, not mixed WITHSCORES).
Use RESP3 (Protocol: 3) for well-structured vector replies.
Upgrade go-redis and Redis to current matching versions.
Compare with redis-cli VSIM output to inspect the raw array.

Example fix

// before: mixed flags yield odd field counts
res, err := rdb.VSimWithAttrib(ctx, "pts", vector)

// after: keep option flags consistent with the parser
// and use RESP3
rdb := redis.NewClient(&redis.Options{Protocol: 3})
res, err := rdb.VSimWithAttrib(ctx, "pts", vector)

Defensive patterns

Strategy: try-catch

Validate before calling

// ensure flags match the parser
// VSIM key vector WITHATTRIBS -> use VSimWithAttrib, 2 fields per element

Try / catch

cmd := rdb.VSimWithAttrib(ctx, "pts", vec)
if err := cmd.Err(); err != nil {
    if strings.Contains(err.Error(), "VSIM array, wanted a multiple of 2") {
        // fall back to raw Do() or the score-only variant
    }
    return err
}

Prevention

Use the command variant matching your option flags exactly
Prefer RESP3 for vector-set commands
Verify the reply via redis-cli when adding new options
Keep client/server versions aligned

When it happens

Trigger: Calling VSIM with the WITHATTRIBS option (via the attrib-parsing command at command.go:~8825) and receiving an array whose length is not divisible by 2.

Common situations: Server/client version skew on VSIM reply format; requesting the wrong combination of WITHSCORES/WITHATTRIBS flags so fields per element mismatch; proxies rewriting the reply.

Related errors

AI-assisted analysis of redis/go-redis@c5cad058c7 (2026-09-01). Data as JSON: /api/errors/31763848b1152740. Report an issue: GitHub.