scan

Overview ¶

Package scan has useful functions for handling rows from Query, QueryRow, Exec:

• CollectRows - collects slice of items
• CollectRowsKV - collects map of items
• CollectRow - collects single item

These functions require special row handler row (RowColsCollector, RowColsCollectorKV or RowCollector) that accepts row and should return required type. Basic generic implementation are:

• Direct scanning: DirectCollectorRowCols, DirectCollectorRowColsKV, DirectCollectorRow
• Struct fields by position: StructPosCollectorRowCols, StructPosCollectorRow, StructPosCollectorRowColsKV
• Struct fields by tag: StructTagCollectorRowCols, StructTagCollectorRowColsKV

Examples:

DirectCollectorRowCols:

var ids []int64
rows, _ = db.Query("SELECT id FROM users")
ids, _ = CollectRows(rows, DirectCollectorRowCols[int64])

DirectCollectorRowColsKV:

 var users map[int]string
	rows, _ = db.Query("SELECT id, name FROM users")
	users, _ = CollectRowsKV(rows, DirectCollectorRowColsKV[int64, string])

DirectCollectorRow:

 var name string
	var ok bool
	row = db.QueryRow("SELECT name FROM users where id = $1")
	name, ok, _ = CollectRow(row, DirectCollectorRow[string])

StructTagCollectorRowCols:

 type User struct {
	    Id    int64  `scan:"id"`
	    Name  string `scan:"name"`
	    Email string `scan:"email"`
 }
	var users []User
	rows, _ = db.Query("SELECT id, name, email FROM users")
	users, _ = CollectRows(rows, StructTagCollectorRowCols[User])

StructTagCollectorRowColsKV:

 type User struct {
	    Name  string `scan:"name"`
	    Email string `scan:"email"`
	}
	var users map[int64]User
	rows, _ = db.Query("SELECT id, name, email FROM users")
	users, _ = CollectRowsKV(rows, StructTagCollectorRowColsKV[int64, User])

And so on ...

Package also has Slice for scanning SQL arrays. Example:

 var arr []int
	db.QueryRow(`SELECT ARRAY[1, 2, 3]`).Scan(scan.NewSlice(&arr))

Now arr is [1, 2, 3]