讓 SimpleDB 支援 paging (offset)

在 implement page 的時候通常會用到 SQL 語法的"offset"
取第一頁:

SELECT * FORM `article` OFFSET LIMIT 10

取第二頁:

SELECT * FORM `article` OFFSET LIMIT 10 OFFSET 10

取第三頁:

SELECT * FORM `article` OFFSET LIMIT 10 OFFSET 20

但 AWS SimpleDB 並不支援 offset 這個與法，必須要用 next_token 方式來取
以下用python boto library做個示例：

sdb_conn = SDBConnection(...)

# Skip first 20 items
query = "SELECT COUNT(*) FORM `article` OFFSET LIMIT 20"
rs = sdb_conn.select(sdb_domain, query=query)

# Get target page
query = "SELECT * FORM `article` OFFSET LIMIT 10"
rs2 = sdb_conn.select(sdb_domain, query=query, next_token=rs.next_token)
for item in rs2:
    ...

"SELECT COUNT(*)" 是最有效率的略過方法，如果用"SELECT * "則會有 return 2500 rows 的限制！


 參考資料

• Chris Moyer: Paging SDB results in boto
• AWS Developer Forums: There is LIMIT, but is there LIMIT 40, ...