本文整理汇总了Python中cqlengine.statements.UpdateStatement.get_context_size方法的典型用法代码示例。如果您正苦于以下问题：Python UpdateStatement.get_context_size方法的具体用法？Python UpdateStatement.get_context_size怎么用？Python UpdateStatement.get_context_size使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类cqlengine.statements.UpdateStatement的用法示例。
在下文中一共展示了UpdateStatement.get_context_size方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Python代码示例。
示例1: update
# 需要导入模块: from cqlengine.statements import UpdateStatement [as 别名]
# 或者: from cqlengine.statements.UpdateStatement import get_context_size [as 别名]
def update(self):
"""
updates a row.
This is a blind update call.
All validation and cleaning needs to happen
prior to calling this.
"""
if self.instance is None:
raise CQLEngineException("DML Query intance attribute is None")
assert type(self.instance) == self.model
static_update_only = True
statement = UpdateStatement(self.column_family_name, ttl=self._ttl,
timestamp=self._timestamp, transactions=self._transaction)
#get defined fields and their column names
for name, col in self.model._columns.items():
if not col.is_primary_key:
val = getattr(self.instance, name, None)
val_mgr = self.instance._values[name]
# don't update something that is null
if val is None:
continue
# don't update something if it hasn't changed
if not val_mgr.changed and not isinstance(col, Counter):
continue
static_update_only = (static_update_only and col.static)
if isinstance(col, (BaseContainerColumn, Counter)):
# get appropriate clause
if isinstance(col, List): klass = ListUpdateClause
elif isinstance(col, Map): klass = MapUpdateClause
elif isinstance(col, Set): klass = SetUpdateClause
elif isinstance(col, Counter): klass = CounterUpdateClause
else: raise RuntimeError
# do the stuff
clause = klass(col.db_field_name, val,
previous=val_mgr.previous_value, column=col)
if clause.get_context_size() > 0:
statement.add_assignment_clause(clause)
else:
statement.add_assignment_clause(AssignmentClause(
col.db_field_name,
col.to_database(val)
))
if statement.get_context_size() > 0 or self.instance._has_counter:
for name, col in self.model._primary_keys.items():
if static_update_only and (not col.partition_key):
continue
statement.add_where_clause(WhereClause(
col.db_field_name,
EqualsOperator(),
col.to_database(getattr(self.instance, name))
))
self._execute(statement)
self._delete_null_columns()