137 lines
3.5 KiB
Go
137 lines
3.5 KiB
Go
package cassandra
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import (
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"fmt"
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"reflect"
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"sync"
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"unicode"
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"github.com/scylladb/gocqlx/v3/table"
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)
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var (
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// metadataCache 快取已生成的 Metadata，避免重複反射解析
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// key: tableName + ":" + structType (不包含 keyspace，因為同一個 struct 在不同 keyspace 結構相同)
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metadataCache sync.Map
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)
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type cachedMetadata struct {
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columns []string
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partKeys []string
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sortKeys []string
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err error
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}
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// generateMetadata 根據傳入的 struct 產生 table.Metadata
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// 使用快取機制避免重複反射解析，提升效能
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func generateMetadata[T Table](doc T, keyspace string) (table.Metadata, error) {
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// 取得型別資訊
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t := reflect.TypeOf(doc)
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if t.Kind() == reflect.Ptr {
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t = t.Elem()
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}
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// 取得表名稱
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tableName := doc.TableName()
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if tableName == "" {
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return table.Metadata{}, ErrMissingTableName
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}
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// 構建快取 key: tableName:structType (不包含 keyspace)
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cacheKey := fmt.Sprintf("%s:%s", tableName, t.String())
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// 檢查快取
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if cached, ok := metadataCache.Load(cacheKey); ok {
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cachedMeta := cached.(cachedMetadata)
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if cachedMeta.err != nil {
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return table.Metadata{}, cachedMeta.err
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}
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// 從快取構建 metadata，動態加上 keyspace
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meta := table.Metadata{
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Name: fmt.Sprintf("%s.%s", keyspace, tableName),
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Columns: make([]string, len(cachedMeta.columns)),
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PartKey: make([]string, len(cachedMeta.partKeys)),
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SortKey: make([]string, len(cachedMeta.sortKeys)),
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}
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copy(meta.Columns, cachedMeta.columns)
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copy(meta.PartKey, cachedMeta.partKeys)
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copy(meta.SortKey, cachedMeta.sortKeys)
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return meta, nil
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}
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// 快取未命中，生成 metadata
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columns := make([]string, 0, t.NumField())
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partKeys := make([]string, 0, t.NumField())
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sortKeys := make([]string, 0, t.NumField())
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// 遍歷所有 exported 欄位
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for i := 0; i < t.NumField(); i++ {
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field := t.Field(i)
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// 跳過 unexported 欄位
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if field.PkgPath != "" {
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continue
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}
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// 如果欄位有標記 db:"-" 則跳過
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if tag := field.Tag.Get("db"); tag == "-" {
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continue
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}
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// 取得欄位名稱
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colName := field.Tag.Get("db")
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if colName == "" {
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colName = toSnakeCase(field.Name)
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}
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columns = append(columns, colName)
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// 若有 partition_key:"true" 標記，加入 PartKey
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if field.Tag.Get("partition_key") == "true" {
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partKeys = append(partKeys, colName)
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}
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// 若有 clustering_key:"true" 標記，加入 SortKey
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if field.Tag.Get("clustering_key") == "true" {
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sortKeys = append(sortKeys, colName)
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}
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}
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if len(partKeys) == 0 {
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err := ErrNoPartitionKey
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// 快取錯誤結果
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metadataCache.Store(cacheKey, cachedMetadata{err: err})
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return table.Metadata{}, err
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}
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// 快取成功結果（只存結構資訊，不包含 keyspace）
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cachedMeta := cachedMetadata{
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columns: make([]string, len(columns)),
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partKeys: make([]string, len(partKeys)),
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sortKeys: make([]string, len(sortKeys)),
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}
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copy(cachedMeta.columns, columns)
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copy(cachedMeta.partKeys, partKeys)
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copy(cachedMeta.sortKeys, sortKeys)
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metadataCache.Store(cacheKey, cachedMeta)
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// 組合並返回 Metadata（包含 keyspace）
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meta := table.Metadata{
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Name: fmt.Sprintf("%s.%s", keyspace, tableName),
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Columns: columns,
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PartKey: partKeys,
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SortKey: sortKeys,
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}
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return meta, nil
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}
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// toSnakeCase 將 CamelCase 字串轉換為 snake_case
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func toSnakeCase(s string) string {
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var result []rune
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for i, r := range s {
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if unicode.IsUpper(r) {
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if i > 0 {
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result = append(result, '_')
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}
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result = append(result, unicode.ToLower(r))
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} else {
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result = append(result, r)
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}
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}
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return string(result)
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}
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