Function schemaToFieldDescriptions

server/doltgres_handler.go:498–554

(ctx *sql.Context, s sql.Schema, formatCodes []int16)

}

func schemaToFieldDescriptions(ctx *sql.Context, s sql.Schema, formatCodes []int16) ([]pgproto3.FieldDescription, error) {
	var err error
	formatCodes, err = extendFormatCodes(len(s), formatCodes)
	if err != nil {
		return nil, err
	}

	fields := make([]pgproto3.FieldDescription, len(s))
	for i, c := range s {
		var oid uint32
		var typmod = int32(-1)

		var err error
		colName := c.Name
		// Translate the internal sentinel aliases set by nodeSelectExprs for unaliased string
		// literals back to Postgres's ?column? placeholder.
		if strings.HasPrefix(colName, ast.UnknownColSentinelPrefix) {
			colName = "?column?"
		}
		dataTypeSize := int16(c.Type.MaxTextResponseByteLength(ctx))
		tableAttributeNumber := uint16(i + 1) // TODO: this should be based on the actual table field index, not the return schema
		if doltgresType, ok := c.Type.(*pgtypes.DoltgresType); ok {
			if doltgresType.ID == pgtypes.Unknown.ID {
				// The `unknown` type is always converted to `text` on output since they're binary coercible.
				// No function or column returns `unknown`, so this is always a raw string literal from the query.
				// Column naming (alias vs ?column?) is handled in nodeSelectExprs; preserve whatever name
				// was set there.
				doltgresType = pgtypes.Text
				dataTypeSize = int16(doltgresType.MaxTextResponseByteLength(ctx))
				tableAttributeNumber = 0
			}
			if doltgresType.TypType == pgtypes.TypeType_Domain {
				oid = id.Cache().ToOID(doltgresType.BaseTypeType.ID.AsId())
			} else {
				oid = id.Cache().ToOID(doltgresType.ID.AsId())
			}
			typmod = doltgresType.GetAttTypMod() // pg_attribute.atttypmod
		} else {
			oid, err = VitessTypeToObjectID(c.Type)
			if err != nil {
				panic(err)
			}
		}

		fields[i] = pgproto3.FieldDescription{
			Name:                 []byte(colName),
			TableOID:             uint32(0),
			TableAttributeNumber: tableAttributeNumber,
			DataTypeOID:          oid,
			DataTypeSize:         dataTypeSize,
			TypeModifier:         typmod,
			Format:               formatCodes[i],
		}
	}

	return fields, nil
}