93 lines
2.9 KiB
Python
93 lines
2.9 KiB
Python
# -*- coding: utf-8 -*-
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"""SCD2 (Slowly Changing Dimension Type 2) 处理器"""
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from datetime import datetime
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class SCD2Handler:
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"""SCD2历史记录处理器"""
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def __init__(self, db_ops):
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self.db = db_ops
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def upsert(self, table_name: str, natural_key: list, tracked_fields: list,
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record: dict, effective_date: datetime = None) -> str:
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"""
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处理SCD2更新
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Args:
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table_name: 表名
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natural_key: 自然键字段列表
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tracked_fields: 需要跟踪变化的字段列表
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record: 记录数据
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effective_date: 生效日期
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Returns:
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操作类型: 'INSERT', 'UPDATE', 'UNCHANGED'
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"""
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effective_date = effective_date or datetime.now()
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# 查找当前有效记录
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where_clause = " AND ".join([f"{k} = %({k})s" for k in natural_key])
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sql_select = f"""
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SELECT * FROM {table_name}
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WHERE {where_clause}
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AND valid_to IS NULL
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"""
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# 使用 db 的 connection
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current = self.db.conn.cursor()
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current.execute(sql_select, record)
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existing = current.fetchone()
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if not existing:
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# 新记录：直接插入
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record["valid_from"] = effective_date
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record["valid_to"] = None
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record["is_current"] = True
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fields = list(record.keys())
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placeholders = ", ".join([f"%({f})s" for f in fields])
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sql_insert = f"""
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INSERT INTO {table_name} ({', '.join(fields)})
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VALUES ({placeholders})
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"""
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current.execute(sql_insert, record)
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return 'INSERT'
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# 检查是否有变化
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has_changes = any(
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existing.get(field) != record.get(field)
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for field in tracked_fields
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)
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if not has_changes:
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return 'UNCHANGED'
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# 有变化：关闭旧记录，插入新记录
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update_where = " AND ".join([f"{k} = %({k})s" for k in natural_key])
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sql_close = f"""
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UPDATE {table_name}
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SET valid_to = %(effective_date)s,
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is_current = FALSE
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WHERE {update_where}
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AND valid_to IS NULL
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"""
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record["effective_date"] = effective_date
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current.execute(sql_close, record)
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# 插入新记录
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record["valid_from"] = effective_date
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record["valid_to"] = None
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record["is_current"] = True
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fields = list(record.keys())
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if "effective_date" in fields:
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fields.remove("effective_date")
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placeholders = ", ".join([f"%({f})s" for f in fields])
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sql_insert = f"""
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INSERT INTO {table_name} ({', '.join(fields)})
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VALUES ({placeholders})
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"""
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current.execute(sql_insert, record)
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return 'UPDATE'
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