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"""
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Code to generate a Python model from a database or differences
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between a model and database.
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Some of this is borrowed heavily from the AutoCode project at:
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http://code.google.com/p/sqlautocode/
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"""
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import sys
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import logging
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import sqlalchemy
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from rhodecode.lib.dbmigrate import migrate
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from rhodecode.lib.dbmigrate.migrate import changeset
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log = logging.getLogger(__name__)
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HEADER = """
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## File autogenerated by genmodel.py
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from sqlalchemy import *
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meta = MetaData()
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"""
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DECLARATIVE_HEADER = """
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## File autogenerated by genmodel.py
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from sqlalchemy import *
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from sqlalchemy.ext import declarative
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Base = declarative.declarative_base()
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"""
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class ModelGenerator(object):
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"""Various transformations from an A, B diff.
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In the implementation, A tends to be called the model and B
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the database (although this is not true of all diffs).
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The diff is directionless, but transformations apply the diff
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in a particular direction, described in the method name.
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"""
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def __init__(self, diff, engine, declarative=False):
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self.diff = diff
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self.engine = engine
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self.declarative = declarative
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def column_repr(self, col):
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kwarg = []
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if col.key != col.name:
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kwarg.append('key')
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if col.primary_key:
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col.primary_key = True # otherwise it dumps it as 1
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kwarg.append('primary_key')
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if not col.nullable:
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kwarg.append('nullable')
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if col.onupdate:
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kwarg.append('onupdate')
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if col.default:
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if col.primary_key:
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# I found that PostgreSQL automatically creates a
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# default value for the sequence, but let's not show
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# that.
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pass
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else:
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kwarg.append('default')
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args = ['%s=%r' % (k, getattr(col, k)) for k in kwarg]
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# crs: not sure if this is good idea, but it gets rid of extra
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# u''
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name = col.name.encode('utf8')
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type_ = col.type
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for cls in col.type.__class__.__mro__:
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if cls.__module__ == 'sqlalchemy.types' and \
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not cls.__name__.isupper():
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if cls is not type_.__class__:
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type_ = cls()
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break
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type_repr = repr(type_)
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if type_repr.endswith('()'):
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type_repr = type_repr[:-2]
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constraints = [repr(cn) for cn in col.constraints]
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data = {
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'name': name,
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'commonStuff': ', '.join([type_repr] + constraints + args),
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}
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if self.declarative:
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return """%(name)s = Column(%(commonStuff)s)""" % data
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else:
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return """Column(%(name)r, %(commonStuff)s)""" % data
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def _getTableDefn(self, table, metaName='meta'):
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out = []
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tableName = table.name
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if self.declarative:
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out.append("class %(table)s(Base):" % {'table': tableName})
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out.append(" __tablename__ = '%(table)s'\n" %
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{'table': tableName})
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for col in table.columns:
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out.append(" %s" % self.column_repr(col))
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out.append('\n')
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else:
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out.append("%(table)s = Table('%(table)s', %(meta)s," %
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{'table': tableName, 'meta': metaName})
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for col in table.columns:
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out.append(" %s," % self.column_repr(col))
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out.append(")\n")
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return out
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def _get_tables(self,missingA=False,missingB=False,modified=False):
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to_process = []
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for bool_,names,metadata in (
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(missingA,self.diff.tables_missing_from_A,self.diff.metadataB),
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(missingB,self.diff.tables_missing_from_B,self.diff.metadataA),
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(modified,self.diff.tables_different,self.diff.metadataA),
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):
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if bool_:
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for name in names:
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yield metadata.tables.get(name)
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def genBDefinition(self):
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"""Generates the source code for a definition of B.
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Assumes a diff where A is empty.
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Was: toPython. Assume database (B) is current and model (A) is empty.
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"""
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out = []
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if self.declarative:
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out.append(DECLARATIVE_HEADER)
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else:
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out.append(HEADER)
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out.append("")
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for table in self._get_tables(missingA=True):
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out.extend(self._getTableDefn(table))
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return '\n'.join(out)
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def genB2AMigration(self, indent=' '):
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"""Generate a migration from B to A.
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Was: toUpgradeDowngradePython
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Assume model (A) is most current and database (B) is out-of-date.
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"""
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decls = ['from migrate.changeset import schema',
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'pre_meta = MetaData()',
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'post_meta = MetaData()',
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]
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upgradeCommands = ['pre_meta.bind = migrate_engine',
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'post_meta.bind = migrate_engine']
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downgradeCommands = list(upgradeCommands)
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for tn in self.diff.tables_missing_from_A:
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pre_table = self.diff.metadataB.tables[tn]
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decls.extend(self._getTableDefn(pre_table, metaName='pre_meta'))
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upgradeCommands.append(
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"pre_meta.tables[%(table)r].drop()" % {'table': tn})
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downgradeCommands.append(
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"pre_meta.tables[%(table)r].create()" % {'table': tn})
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for tn in self.diff.tables_missing_from_B:
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post_table = self.diff.metadataA.tables[tn]
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decls.extend(self._getTableDefn(post_table, metaName='post_meta'))
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upgradeCommands.append(
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"post_meta.tables[%(table)r].create()" % {'table': tn})
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downgradeCommands.append(
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"post_meta.tables[%(table)r].drop()" % {'table': tn})
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for (tn, td) in self.diff.tables_different.iteritems():
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if td.columns_missing_from_A or td.columns_different:
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pre_table = self.diff.metadataB.tables[tn]
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decls.extend(self._getTableDefn(
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pre_table, metaName='pre_meta'))
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if td.columns_missing_from_B or td.columns_different:
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post_table = self.diff.metadataA.tables[tn]
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decls.extend(self._getTableDefn(
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post_table, metaName='post_meta'))
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for col in td.columns_missing_from_A:
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upgradeCommands.append(
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'pre_meta.tables[%r].columns[%r].drop()' % (tn, col))
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downgradeCommands.append(
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'pre_meta.tables[%r].columns[%r].create()' % (tn, col))
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for col in td.columns_missing_from_B:
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upgradeCommands.append(
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'post_meta.tables[%r].columns[%r].create()' % (tn, col))
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downgradeCommands.append(
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'post_meta.tables[%r].columns[%r].drop()' % (tn, col))
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for modelCol, databaseCol, modelDecl, databaseDecl in td.columns_different:
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upgradeCommands.append(
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'assert False, "Can\'t alter columns: %s:%s=>%s"' % (
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tn, modelCol.name, databaseCol.name))
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downgradeCommands.append(
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'assert False, "Can\'t alter columns: %s:%s=>%s"' % (
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tn, modelCol.name, databaseCol.name))
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return (
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'\n'.join(decls),
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'\n'.join('%s%s' % (indent, line) for line in upgradeCommands),
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'\n'.join('%s%s' % (indent, line) for line in downgradeCommands))
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def _db_can_handle_this_change(self,td):
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"""Check if the database can handle going from B to A."""
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if (td.columns_missing_from_B
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and not td.columns_missing_from_A
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and not td.columns_different):
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# Even sqlite can handle column additions.
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return True
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else:
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return not self.engine.url.drivername.startswith('sqlite')
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def runB2A(self):
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"""Goes from B to A.
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Was: applyModel. Apply model (A) to current database (B).
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"""
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meta = sqlalchemy.MetaData(self.engine)
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for table in self._get_tables(missingA=True):
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table = table.tometadata(meta)
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table.drop()
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for table in self._get_tables(missingB=True):
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table = table.tometadata(meta)
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table.create()
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for modelTable in self._get_tables(modified=True):
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tableName = modelTable.name
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modelTable = modelTable.tometadata(meta)
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dbTable = self.diff.metadataB.tables[tableName]
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td = self.diff.tables_different[tableName]
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if self._db_can_handle_this_change(td):
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for col in td.columns_missing_from_B:
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modelTable.columns[col].create()
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for col in td.columns_missing_from_A:
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dbTable.columns[col].drop()
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# XXX handle column changes here.
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else:
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# Sqlite doesn't support drop column, so you have to
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# do more: create temp table, copy data to it, drop
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# old table, create new table, copy data back.
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#
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# I wonder if this is guaranteed to be unique?
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tempName = '_temp_%s' % modelTable.name
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def getCopyStatement():
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preparer = self.engine.dialect.preparer
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commonCols = []
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for modelCol in modelTable.columns:
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if modelCol.name in dbTable.columns:
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commonCols.append(modelCol.name)
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commonColsStr = ', '.join(commonCols)
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return 'INSERT INTO %s (%s) SELECT %s FROM %s' % \
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(tableName, commonColsStr, commonColsStr, tempName)
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# Move the data in one transaction, so that we don't
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# leave the database in a nasty state.
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connection = self.engine.connect()
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trans = connection.begin()
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try:
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connection.execute(
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'CREATE TEMPORARY TABLE %s as SELECT * from %s' % \
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(tempName, modelTable.name))
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# make sure the drop takes place inside our
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# transaction with the bind parameter
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modelTable.drop(bind=connection)
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modelTable.create(bind=connection)
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connection.execute(getCopyStatement())
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connection.execute('DROP TABLE %s' % tempName)
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trans.commit()
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except:
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trans.rollback()
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raise
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