Re: [I] Feature Request: Support Vector Type [cassandra-gocql-driver]

["rcosnita (via GitHub)" <gi...@apache.org>]

rcosnita commented on issue #1734:
URL: https://github.com/apache/cassandra-gocql-driver/issues/1734#issuecomment-2327419047

   Hello everyone,
   
   For people who are using version 4 of the protocol but need to be able to write vectors from their code base here is a possible idea:
   
   ```go
   package warm
   
   import (
   	"fmt"
   
   	"github.com/gocql/gocql"
   )
   
   func encInt(v int32) []byte {
   	return []byte{byte(v >> 24), byte(v >> 16), byte(v >> 8), byte(v)}
   }
   
   func encFloat(v float32) []byte {
   	return encInt(int32(math.Float32bits(v)))
   }
   
   type Float32Vector struct {
   	value      []float32
   	dimensions int
   }
   
   func (m *Float32Vector) MarshalCQL(info gocql.TypeInfo) ([]byte, error) {
   	if len(m.value) != m.dimensions {
   		return nil, fmt.Errorf("float32vector expects size %d but received size %d",
   			m.dimensions, len(m.value))
   	}
   
   	var results []byte
   	for _, part := range m.value {
   		results = append(results, encFloat(part)...)
   	}
   
   	return results, nil
   }
   
   func (m *Float32Vector) UnmarshalCQL(info gocql.TypeInfo, data []byte) error {
   	panic("unmarshalling vector is not fully implemented")
   }
   
   func (m *Float32Vector) Value() []float32 {
   	return m.value
   }
   
   func ensureVectorDimension(values []float32, dimensions int) []float32 {
   	if len(values) == dimensions {
   		return values
   	}
   
   	delta := dimensions - len(values)
   	result := make([]float32, dimensions)
   	for idx, v := range values {
   		if idx < dimensions {
   			result[idx] = v
   		} else {
                      break
                   }
   	}
   
   	for idx := len(values); idx < delta+len(values); idx++ {
   		result[idx] = 0.0
   	}
   
   	return result
   }
   
   func FromVectorFloat32(value []float32, dimensions int) *Float32Vector {
   	return &Float32Vector{
   		value:      ensureVectorDimension(value, dimensions),
   		dimensions: dimensions,
   	}
   }
   ```
   
   You can opt to skip the padding completely and return an error if that feels more natural for your use case. The encoding functions are extracted from the existing gocql codebase.


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