606 lines
19 KiB
Python
606 lines
19 KiB
Python
# sql/util.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""High level utilities which build upon other modules here.
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"""
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from .. import exc, util
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from .base import _from_objects, ColumnSet
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from . import operators, visitors
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from itertools import chain
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from collections import deque
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from .elements import BindParameter, ColumnClause, ColumnElement, \
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Null, UnaryExpression, literal_column, Label
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from .selectable import ScalarSelect, Join, FromClause, FromGrouping
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from .schema import Column
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join_condition = util.langhelpers.public_factory(
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Join._join_condition,
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".sql.util.join_condition")
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# names that are still being imported from the outside
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from .annotation import _shallow_annotate, _deep_annotate, _deep_deannotate
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from .elements import _find_columns
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from .ddl import sort_tables
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def find_join_source(clauses, join_to):
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"""Given a list of FROM clauses and a selectable,
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return the first index and element from the list of
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clauses which can be joined against the selectable. returns
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None, None if no match is found.
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e.g.::
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clause1 = table1.join(table2)
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clause2 = table4.join(table5)
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join_to = table2.join(table3)
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find_join_source([clause1, clause2], join_to) == clause1
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"""
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selectables = list(_from_objects(join_to))
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for i, f in enumerate(clauses):
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for s in selectables:
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if f.is_derived_from(s):
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return i, f
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else:
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return None, None
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def visit_binary_product(fn, expr):
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"""Produce a traversal of the given expression, delivering
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column comparisons to the given function.
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The function is of the form::
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def my_fn(binary, left, right)
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For each binary expression located which has a
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comparison operator, the product of "left" and
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"right" will be delivered to that function,
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in terms of that binary.
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Hence an expression like::
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and_(
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(a + b) == q + func.sum(e + f),
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j == r
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)
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would have the traversal::
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a <eq> q
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a <eq> e
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a <eq> f
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b <eq> q
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b <eq> e
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b <eq> f
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j <eq> r
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That is, every combination of "left" and
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"right" that doesn't further contain
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a binary comparison is passed as pairs.
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"""
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stack = []
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def visit(element):
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if isinstance(element, ScalarSelect):
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# we don't want to dig into correlated subqueries,
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# those are just column elements by themselves
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yield element
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elif element.__visit_name__ == 'binary' and \
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operators.is_comparison(element.operator):
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stack.insert(0, element)
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for l in visit(element.left):
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for r in visit(element.right):
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fn(stack[0], l, r)
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stack.pop(0)
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for elem in element.get_children():
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visit(elem)
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else:
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if isinstance(element, ColumnClause):
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yield element
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for elem in element.get_children():
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for e in visit(elem):
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yield e
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list(visit(expr))
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def find_tables(clause, check_columns=False,
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include_aliases=False, include_joins=False,
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include_selects=False, include_crud=False):
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"""locate Table objects within the given expression."""
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tables = []
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_visitors = {}
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if include_selects:
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_visitors['select'] = _visitors['compound_select'] = tables.append
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if include_joins:
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_visitors['join'] = tables.append
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if include_aliases:
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_visitors['alias'] = tables.append
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if include_crud:
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_visitors['insert'] = _visitors['update'] = \
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_visitors['delete'] = lambda ent: tables.append(ent.table)
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if check_columns:
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def visit_column(column):
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tables.append(column.table)
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_visitors['column'] = visit_column
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_visitors['table'] = tables.append
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visitors.traverse(clause, {'column_collections': False}, _visitors)
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return tables
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def unwrap_order_by(clause):
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"""Break up an 'order by' expression into individual column-expressions,
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without DESC/ASC/NULLS FIRST/NULLS LAST"""
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cols = util.column_set()
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stack = deque([clause])
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while stack:
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t = stack.popleft()
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if isinstance(t, ColumnElement) and \
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(
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not isinstance(t, UnaryExpression) or
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not operators.is_ordering_modifier(t.modifier)
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):
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cols.add(t)
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else:
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for c in t.get_children():
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stack.append(c)
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return cols
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def clause_is_present(clause, search):
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"""Given a target clause and a second to search within, return True
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if the target is plainly present in the search without any
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subqueries or aliases involved.
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Basically descends through Joins.
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"""
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for elem in surface_selectables(search):
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if clause == elem: # use == here so that Annotated's compare
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return True
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else:
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return False
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def surface_selectables(clause):
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stack = [clause]
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while stack:
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elem = stack.pop()
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yield elem
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if isinstance(elem, Join):
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stack.extend((elem.left, elem.right))
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elif isinstance(elem, FromGrouping):
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stack.append(elem.element)
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def selectables_overlap(left, right):
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"""Return True if left/right have some overlapping selectable"""
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return bool(
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set(surface_selectables(left)).intersection(
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surface_selectables(right)
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)
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)
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def bind_values(clause):
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"""Return an ordered list of "bound" values in the given clause.
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E.g.::
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>>> expr = and_(
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... table.c.foo==5, table.c.foo==7
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... )
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>>> bind_values(expr)
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[5, 7]
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"""
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v = []
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def visit_bindparam(bind):
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v.append(bind.effective_value)
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visitors.traverse(clause, {}, {'bindparam': visit_bindparam})
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return v
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def _quote_ddl_expr(element):
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if isinstance(element, util.string_types):
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element = element.replace("'", "''")
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return "'%s'" % element
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else:
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return repr(element)
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class _repr_params(object):
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"""A string view of bound parameters, truncating
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display to the given number of 'multi' parameter sets.
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"""
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def __init__(self, params, batches):
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self.params = params
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self.batches = batches
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def __repr__(self):
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if isinstance(self.params, (list, tuple)) and \
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len(self.params) > self.batches and \
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isinstance(self.params[0], (list, dict, tuple)):
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msg = " ... displaying %i of %i total bound parameter sets ... "
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return ' '.join((
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repr(self.params[:self.batches - 2])[0:-1],
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msg % (self.batches, len(self.params)),
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repr(self.params[-2:])[1:]
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))
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else:
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return repr(self.params)
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def adapt_criterion_to_null(crit, nulls):
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"""given criterion containing bind params, convert selected elements
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to IS NULL.
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"""
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def visit_binary(binary):
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if isinstance(binary.left, BindParameter) \
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and binary.left._identifying_key in nulls:
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# reverse order if the NULL is on the left side
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binary.left = binary.right
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binary.right = Null()
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binary.operator = operators.is_
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binary.negate = operators.isnot
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elif isinstance(binary.right, BindParameter) \
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and binary.right._identifying_key in nulls:
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binary.right = Null()
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binary.operator = operators.is_
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binary.negate = operators.isnot
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return visitors.cloned_traverse(crit, {}, {'binary': visit_binary})
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def splice_joins(left, right, stop_on=None):
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if left is None:
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return right
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stack = [(right, None)]
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adapter = ClauseAdapter(left)
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ret = None
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while stack:
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(right, prevright) = stack.pop()
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if isinstance(right, Join) and right is not stop_on:
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right = right._clone()
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right._reset_exported()
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right.onclause = adapter.traverse(right.onclause)
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stack.append((right.left, right))
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else:
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right = adapter.traverse(right)
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if prevright is not None:
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prevright.left = right
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if ret is None:
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ret = right
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return ret
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def reduce_columns(columns, *clauses, **kw):
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"""given a list of columns, return a 'reduced' set based on natural
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equivalents.
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the set is reduced to the smallest list of columns which have no natural
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equivalent present in the list. A "natural equivalent" means that two
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columns will ultimately represent the same value because they are related
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by a foreign key.
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\*clauses is an optional list of join clauses which will be traversed
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to further identify columns that are "equivalent".
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\**kw may specify 'ignore_nonexistent_tables' to ignore foreign keys
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whose tables are not yet configured, or columns that aren't yet present.
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This function is primarily used to determine the most minimal "primary
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key" from a selectable, by reducing the set of primary key columns present
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in the selectable to just those that are not repeated.
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"""
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ignore_nonexistent_tables = kw.pop('ignore_nonexistent_tables', False)
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only_synonyms = kw.pop('only_synonyms', False)
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columns = util.ordered_column_set(columns)
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omit = util.column_set()
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for col in columns:
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for fk in chain(*[c.foreign_keys for c in col.proxy_set]):
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for c in columns:
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if c is col:
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continue
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try:
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fk_col = fk.column
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except exc.NoReferencedColumnError:
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# TODO: add specific coverage here
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# to test/sql/test_selectable ReduceTest
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if ignore_nonexistent_tables:
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continue
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else:
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raise
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except exc.NoReferencedTableError:
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# TODO: add specific coverage here
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# to test/sql/test_selectable ReduceTest
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if ignore_nonexistent_tables:
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continue
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else:
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raise
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if fk_col.shares_lineage(c) and \
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(not only_synonyms or
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c.name == col.name):
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omit.add(col)
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break
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if clauses:
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def visit_binary(binary):
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if binary.operator == operators.eq:
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cols = util.column_set(
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chain(*[c.proxy_set for c in columns.difference(omit)]))
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if binary.left in cols and binary.right in cols:
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for c in reversed(columns):
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if c.shares_lineage(binary.right) and \
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(not only_synonyms or
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c.name == binary.left.name):
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omit.add(c)
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break
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for clause in clauses:
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if clause is not None:
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visitors.traverse(clause, {}, {'binary': visit_binary})
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return ColumnSet(columns.difference(omit))
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def criterion_as_pairs(expression, consider_as_foreign_keys=None,
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consider_as_referenced_keys=None, any_operator=False):
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"""traverse an expression and locate binary criterion pairs."""
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if consider_as_foreign_keys and consider_as_referenced_keys:
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raise exc.ArgumentError("Can only specify one of "
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"'consider_as_foreign_keys' or "
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"'consider_as_referenced_keys'")
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def col_is(a, b):
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# return a is b
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return a.compare(b)
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def visit_binary(binary):
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if not any_operator and binary.operator is not operators.eq:
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return
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if not isinstance(binary.left, ColumnElement) or \
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not isinstance(binary.right, ColumnElement):
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return
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if consider_as_foreign_keys:
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if binary.left in consider_as_foreign_keys and \
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(col_is(binary.right, binary.left) or
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binary.right not in consider_as_foreign_keys):
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pairs.append((binary.right, binary.left))
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elif binary.right in consider_as_foreign_keys and \
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(col_is(binary.left, binary.right) or
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binary.left not in consider_as_foreign_keys):
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pairs.append((binary.left, binary.right))
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elif consider_as_referenced_keys:
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if binary.left in consider_as_referenced_keys and \
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(col_is(binary.right, binary.left) or
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binary.right not in consider_as_referenced_keys):
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pairs.append((binary.left, binary.right))
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elif binary.right in consider_as_referenced_keys and \
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(col_is(binary.left, binary.right) or
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binary.left not in consider_as_referenced_keys):
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pairs.append((binary.right, binary.left))
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else:
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if isinstance(binary.left, Column) and \
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isinstance(binary.right, Column):
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if binary.left.references(binary.right):
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pairs.append((binary.right, binary.left))
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elif binary.right.references(binary.left):
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pairs.append((binary.left, binary.right))
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pairs = []
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visitors.traverse(expression, {}, {'binary': visit_binary})
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return pairs
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class AliasedRow(object):
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"""Wrap a RowProxy with a translation map.
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This object allows a set of keys to be translated
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to those present in a RowProxy.
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"""
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def __init__(self, row, map):
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# AliasedRow objects don't nest, so un-nest
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# if another AliasedRow was passed
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if isinstance(row, AliasedRow):
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self.row = row.row
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else:
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self.row = row
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self.map = map
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def __contains__(self, key):
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return self.map[key] in self.row
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def has_key(self, key):
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return key in self
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def __getitem__(self, key):
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return self.row[self.map[key]]
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def keys(self):
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return self.row.keys()
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class ClauseAdapter(visitors.ReplacingCloningVisitor):
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"""Clones and modifies clauses based on column correspondence.
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E.g.::
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table1 = Table('sometable', metadata,
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Column('col1', Integer),
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Column('col2', Integer)
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)
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table2 = Table('someothertable', metadata,
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Column('col1', Integer),
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Column('col2', Integer)
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)
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condition = table1.c.col1 == table2.c.col1
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make an alias of table1::
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s = table1.alias('foo')
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calling ``ClauseAdapter(s).traverse(condition)`` converts
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condition to read::
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s.c.col1 == table2.c.col1
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"""
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def __init__(self, selectable, equivalents=None,
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include=None, exclude=None,
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include_fn=None, exclude_fn=None,
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adapt_on_names=False):
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self.__traverse_options__ = {'stop_on': [selectable]}
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self.selectable = selectable
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if include:
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assert not include_fn
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self.include_fn = lambda e: e in include
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else:
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self.include_fn = include_fn
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if exclude:
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assert not exclude_fn
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self.exclude_fn = lambda e: e in exclude
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else:
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self.exclude_fn = exclude_fn
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self.equivalents = util.column_dict(equivalents or {})
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self.adapt_on_names = adapt_on_names
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def _corresponding_column(self, col, require_embedded,
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_seen=util.EMPTY_SET):
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newcol = self.selectable.corresponding_column(
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col,
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require_embedded=require_embedded)
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if newcol is None and col in self.equivalents and col not in _seen:
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for equiv in self.equivalents[col]:
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newcol = self._corresponding_column(
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equiv, require_embedded=require_embedded,
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_seen=_seen.union([col]))
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if newcol is not None:
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return newcol
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if self.adapt_on_names and newcol is None:
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newcol = self.selectable.c.get(col.name)
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return newcol
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magic_flag = False
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def replace(self, col):
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if not self.magic_flag and isinstance(col, FromClause) and \
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self.selectable.is_derived_from(col):
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return self.selectable
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elif not isinstance(col, ColumnElement):
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return None
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elif self.include_fn and not self.include_fn(col):
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return None
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elif self.exclude_fn and self.exclude_fn(col):
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return None
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else:
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return self._corresponding_column(col, True)
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class ColumnAdapter(ClauseAdapter):
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"""Extends ClauseAdapter with extra utility functions.
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Provides the ability to "wrap" this ClauseAdapter
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around another, a columns dictionary which returns
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adapted elements given an original, and an
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adapted_row() factory.
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"""
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def __init__(self, selectable, equivalents=None,
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chain_to=None, include=None,
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exclude=None, adapt_required=False):
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ClauseAdapter.__init__(self, selectable, equivalents,
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include, exclude)
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if chain_to:
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self.chain(chain_to)
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self.columns = util.populate_column_dict(self._locate_col)
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self.adapt_required = adapt_required
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def wrap(self, adapter):
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ac = self.__class__.__new__(self.__class__)
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ac.__dict__ = self.__dict__.copy()
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ac._locate_col = ac._wrap(ac._locate_col, adapter._locate_col)
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|
ac.adapt_clause = ac._wrap(ac.adapt_clause, adapter.adapt_clause)
|
|
ac.adapt_list = ac._wrap(ac.adapt_list, adapter.adapt_list)
|
|
ac.columns = util.populate_column_dict(ac._locate_col)
|
|
return ac
|
|
|
|
adapt_clause = ClauseAdapter.traverse
|
|
adapt_list = ClauseAdapter.copy_and_process
|
|
|
|
def _wrap(self, local, wrapped):
|
|
def locate(col):
|
|
col = local(col)
|
|
return wrapped(col)
|
|
return locate
|
|
|
|
def _locate_col(self, col):
|
|
c = self._corresponding_column(col, True)
|
|
if c is None:
|
|
c = self.adapt_clause(col)
|
|
|
|
# anonymize labels in case they have a hardcoded name
|
|
if isinstance(c, Label):
|
|
c = c.label(None)
|
|
|
|
# adapt_required used by eager loading to indicate that
|
|
# we don't trust a result row column that is not translated.
|
|
# this is to prevent a column from being interpreted as that
|
|
# of the child row in a self-referential scenario, see
|
|
# inheritance/test_basic.py->EagerTargetingTest.test_adapt_stringency
|
|
if self.adapt_required and c is col:
|
|
return None
|
|
|
|
return c
|
|
|
|
def adapted_row(self, row):
|
|
return AliasedRow(row, self.columns)
|
|
|
|
def __getstate__(self):
|
|
d = self.__dict__.copy()
|
|
del d['columns']
|
|
return d
|
|
|
|
def __setstate__(self, state):
|
|
self.__dict__.update(state)
|
|
self.columns = util.PopulateDict(self._locate_col)
|