diff options
Diffstat (limited to 'lib/sqlalchemy/sql/compiler.py')
| -rw-r--r-- | lib/sqlalchemy/sql/compiler.py | 126 |
1 files changed, 92 insertions, 34 deletions
diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py index 9a7646743..8eae0ab7d 100644 --- a/lib/sqlalchemy/sql/compiler.py +++ b/lib/sqlalchemy/sql/compiler.py @@ -28,6 +28,7 @@ import contextlib import itertools import operator import re +import time from . import base from . import coercions @@ -380,6 +381,54 @@ class Compiled(object): sub-elements of the statement can modify these. """ + compile_state = None + """Optional :class:`.CompileState` object that maintains additional + state used by the compiler. + + Major executable objects such as :class:`_expression.Insert`, + :class:`_expression.Update`, :class:`_expression.Delete`, + :class:`_expression.Select` will generate this + state when compiled in order to calculate additional information about the + object. For the top level object that is to be executed, the state can be + stored here where it can also have applicability towards result set + processing. + + .. versionadded:: 1.4 + + """ + + _rewrites_selected_columns = False + """if True, indicates the compile_state object rewrites an incoming + ReturnsRows (like a Select) so that the columns we compile against in the + result set are not what were expressed on the outside. this is a hint to + the execution context to not link the statement.selected_columns to the + columns mapped in the result object. + + That is, when this flag is False:: + + stmt = some_statement() + + result = conn.execute(stmt) + row = result.first() + + # selected_columns are in a 1-1 relationship with the + # columns in the result, and are targetable in mapping + for col in stmt.selected_columns: + assert col in row._mapping + + When True:: + + # selected columns are not what are in the rows. the context + # rewrote the statement for some other set of selected_columns. + for col in stmt.selected_columns: + assert col not in row._mapping + + + """ + + cache_key = None + _gen_time = None + def __init__( self, dialect, @@ -433,6 +482,7 @@ class Compiled(object): self.string = self.preparer._render_schema_translates( self.string, schema_translate_map ) + self._gen_time = time.time() def _execute_on_connection( self, connection, multiparams, params, execution_options @@ -637,28 +687,6 @@ class SQLCompiler(Compiled): insert_prefetch = update_prefetch = () - compile_state = None - """Optional :class:`.CompileState` object that maintains additional - state used by the compiler. - - Major executable objects such as :class:`_expression.Insert`, - :class:`_expression.Update`, :class:`_expression.Delete`, - :class:`_expression.Select` will generate this - state when compiled in order to calculate additional information about the - object. For the top level object that is to be executed, the state can be - stored here where it can also have applicability towards result set - processing. - - .. versionadded:: 1.4 - - """ - - compile_state_factories = util.immutabledict() - """Dictionary of alternate :class:`.CompileState` factories for given - classes, identified by their visit_name. - - """ - def __init__( self, dialect, @@ -667,7 +695,6 @@ class SQLCompiler(Compiled): column_keys=None, inline=False, linting=NO_LINTING, - compile_state_factories=None, **kwargs ): """Construct a new :class:`.SQLCompiler` object. @@ -734,9 +761,6 @@ class SQLCompiler(Compiled): # dialect.label_length or dialect.max_identifier_length self.truncated_names = {} - if compile_state_factories: - self.compile_state_factories = compile_state_factories - Compiled.__init__(self, dialect, statement, **kwargs) if ( @@ -1542,7 +1566,7 @@ class SQLCompiler(Compiled): compile_state = cs._compile_state_factory(cs, self, **kwargs) - if toplevel: + if toplevel and not self.compile_state: self.compile_state = compile_state entry = self._default_stack_entry if toplevel else self.stack[-1] @@ -2541,6 +2565,13 @@ class SQLCompiler(Compiled): ) return froms + translate_select_structure = None + """if none None, should be a callable which accepts (select_stmt, **kw) + and returns a select object. this is used for structural changes + mostly to accommodate for LIMIT/OFFSET schemes + + """ + def visit_select( self, select_stmt, @@ -2552,7 +2583,17 @@ class SQLCompiler(Compiled): from_linter=None, **kwargs ): + assert select_wraps_for is None, ( + "SQLAlchemy 1.4 requires use of " + "the translate_select_structure hook for structural " + "translations of SELECT objects" + ) + # initial setup of SELECT. the compile_state_factory may now + # be creating a totally different SELECT from the one that was + # passed in. for ORM use this will convert from an ORM-state + # SELECT to a regular "Core" SELECT. other composed operations + # such as computation of joins will be performed. compile_state = select_stmt._compile_state_factory( select_stmt, self, **kwargs ) @@ -2560,9 +2601,29 @@ class SQLCompiler(Compiled): toplevel = not self.stack - if toplevel: + if toplevel and not self.compile_state: self.compile_state = compile_state + # translate step for Oracle, SQL Server which often need to + # restructure the SELECT to allow for LIMIT/OFFSET and possibly + # other conditions + if self.translate_select_structure: + new_select_stmt = self.translate_select_structure( + select_stmt, asfrom=asfrom, **kwargs + ) + + # if SELECT was restructured, maintain a link to the originals + # and assemble a new compile state + if new_select_stmt is not select_stmt: + compile_state_wraps_for = compile_state + select_wraps_for = select_stmt + select_stmt = new_select_stmt + + compile_state = select_stmt._compile_state_factory( + select_stmt, self, **kwargs + ) + select_stmt = compile_state.statement + entry = self._default_stack_entry if toplevel else self.stack[-1] populate_result_map = need_column_expressions = ( @@ -2624,13 +2685,9 @@ class SQLCompiler(Compiled): ] if populate_result_map and select_wraps_for is not None: - # if this select is a compiler-generated wrapper, + # if this select was generated from translate_select, # rewrite the targeted columns in the result map - compile_state_wraps_for = select_wraps_for._compile_state_factory( - select_wraps_for, self, **kwargs - ) - translate = dict( zip( [ @@ -3013,7 +3070,8 @@ class SQLCompiler(Compiled): if toplevel: self.isinsert = True - self.compile_state = compile_state + if not self.compile_state: + self.compile_state = compile_state self.stack.append( { |