Class: DynamicMigrations::Postgres::Generator

Inherits:
Object
  • Object
show all
Includes:
Column, Enum, Extension, ForeignKeyConstraint, Function, Index, PrimaryKey, Schema, Table, Trigger, UniqueConstraint, Validation
Defined in:
lib/dynamic_migrations/postgres/generator.rb,
lib/dynamic_migrations/postgres/generator/enum.rb,
lib/dynamic_migrations/postgres/generator/index.rb,
lib/dynamic_migrations/postgres/generator/table.rb,
lib/dynamic_migrations/postgres/generator/column.rb,
lib/dynamic_migrations/postgres/generator/schema.rb,
lib/dynamic_migrations/postgres/generator/trigger.rb,
lib/dynamic_migrations/postgres/generator/fragment.rb,
lib/dynamic_migrations/postgres/generator/function.rb,
lib/dynamic_migrations/postgres/generator/extension.rb,
lib/dynamic_migrations/postgres/generator/migration.rb,
lib/dynamic_migrations/postgres/generator/validation.rb,
lib/dynamic_migrations/postgres/generator/primary_key.rb,
lib/dynamic_migrations/postgres/generator/table_migration.rb,
lib/dynamic_migrations/postgres/generator/schema_migration.rb,
lib/dynamic_migrations/postgres/generator/unique_constraint.rb,
lib/dynamic_migrations/postgres/generator/database_migration.rb,
lib/dynamic_migrations/postgres/generator/trigger_template_base.rb,
lib/dynamic_migrations/postgres/generator/foreign_key_constraint.rb,
lib/dynamic_migrations/postgres/generator/validation_template_base.rb,
lib/dynamic_migrations/postgres/generator/migration_dependency_sorter.rb

Defined Under Namespace

Modules: Column, Enum, Extension, ForeignKeyConstraint, Function, Index, PrimaryKey, Schema, Table, Trigger, UniqueConstraint, Validation Classes: DatabaseMigration, DeferrableOptionsError, ExpectedSymbolError, Fragment, Migration, MigrationDependencySorter, MissingDescriptionError, NoDifferenceError, SchemaMigration, TableMigration, TableMigrationNotFound, TriggerTemplateBase, UnprocessableFragmentError, ValidationTemplateBase

Instance Method Summary collapse

Methods included from Extension

#disable_extension, #enable_extension

Methods included from Enum

#create_enum, #drop_enum, #optional_enum_table, #remove_enum_comment, #set_enum_comment, #update_enum

Methods included from Trigger

add_template, #add_trigger, has_template?, #recreate_trigger, #remove_trigger, #remove_trigger_comment, #set_trigger_comment, template

Methods included from Function

#create_function, #drop_function, #optional_function_table, #remove_function_comment, #set_function_comment, #update_function

Methods included from Validation

add_template, #add_validation, has_template?, #recreate_validation, #remove_validation, #remove_validation_comment, #set_validation_comment, template

Methods included from UniqueConstraint

#add_unique_constraint, #recreate_unique_constraint, #remove_unique_constraint, #remove_unique_constraint_comment, #set_unique_constraint_comment

Methods included from PrimaryKey

#add_primary_key, #recreate_primary_key, #remove_primary_key, #remove_primary_key_comment, #set_primary_key_comment

Methods included from Index

#add_index, #recreate_index, #remove_index, #remove_index_comment, #set_index_comment

Methods included from ForeignKeyConstraint

#add_foreign_key_constraint, #recreate_foreign_key_constraint, #remove_foreign_key_constraint, #remove_foreign_key_constraint_comment, #set_foreign_key_constraint_comment

Methods included from Column

#add_column, #change_column, #remove_column, #remove_column_comment, #set_column_comment

Methods included from Table

#create_table, #drop_table, #remove_table_comment, #set_table_comment

Methods included from Schema

#create_schema, #drop_schema

Constructor Details

#initialize ⇒ Generator

Returns a new instance of Generator.



35
36
37
38
 
# File 'lib/dynamic_migrations/postgres/generator.rb', line 35

def initialize
  @fragments = []
  @logger = Logging.logger[self]
end

Instance Method Details

#migrations ⇒ Object

builds the final migrations



41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
 
# File 'lib/dynamic_migrations/postgres/generator.rb', line 41

def migrations
  log.info "Generating migrations"

  # a hash to hold the generated migrations orgnized by their schema and table
  # this makes it easier and faster to work with them within this method
  database_migrations = {}
  # the database_specific_migrations are for migrations which dont belong
  # within a specific schema, they are important enough that we have a
  # dedicated migration for each one
  database_specific_migrations = []

  # Process each fragment, and organize them into migrations. We create a shared
  # Migration for each table, and a single shared migration for any schema migrations
  # which do not relate to a table.
  log.info "  Organizing migration fragments"
  @fragments.each do |fragment|
    # The first time this schema is encountered we create an object to hold the migrations
    # and organize the different migrations.
    schema_migrations = database_migrations[fragment.schema_name] ||= {
      schema_migration: nil,
      table_migrations: {},
      # this array will hold any migrations which were created by splitting apart table
      # migrations to resolve circular dependencies
      additional_migrations: []
    }
    schema_name = fragment.schema_name
    table_name = fragment.table_name
    # If we have a table name, then add the migration fragment to a
    # TableMigration which holds all of the migrations for this table
    if table_name && schema_name
      table_migration = schema_migrations[:table_migrations][table_name] ||= TableMigration.new(schema_name, table_name)
      table_migration.add_fragment fragment

    # migration fragments which do have a schema, but do not belong to a specific table are added
    # to a dedicated SchemaMigration object
    elsif schema_name && table_name.nil?
      schema_migration = schema_migrations[:schema_migration] ||= SchemaMigration.new(schema_name)
      schema_migration.add_fragment fragment

    # migrations with no schema or table, are added to a database
    # migration (these are really just creating/dropping schemas and extensions)
    elsif schema_name.nil? && table_name.nil?
      database_specific_migration = DatabaseMigration.new
      database_specific_migration.add_fragment(fragment)
      database_specific_migrations << database_specific_migration

    else
      raise UnprocessableFragmentError
    end
  end

  # Convert the hash of migrations into an array of migrations, this is
  # passed to the `circular_dependency?` method below, and any new migrations
  # required to resolve circular dependencies will be added to this array
  all_table_migrations = database_migrations.values.map { |m| m[:table_migrations].values }.flatten

  # For each migration, we recursively traverse the dependency graph to detect and handle circular
  # dependencies.
  #
  # Initially, all the fragments which pertain to a particular table are grouped together in
  # the same migration. If a circular dependency between migrations is detected, then we simply
  # pop the offending migration fragments out of the dedicated table migration and into a new
  # migration. This allows the migration to be processed later, and resolves the circular dependency.
  log.info "  Resolving circular dependencies between migrations"
  completed_table_migrations = []
  all_table_migrations.each do |table_migration|
    # skip it if it's already been processed
    next if completed_table_migrations.include? table_migration
    # recusrsively resolve the circular dependencies for this migration
    resolve_circular_dependencies table_migration, all_table_migrations, database_migrations, completed_table_migrations
  end

  # Prepare a dependency sorter, this is used to sort the migrations via rubys included Tsort module
  # The object used to sort the migrations is extended from a hash, and takes the form:
  # {
  #   # every migration exists as a key, and its corresponding array is all the
  #   # migrations which it depends on
  #   migration1 => [migration2, migration3],
  #   migration3 => [migration2]
  # }
  log.info "  Preparing migrations for sorting"
  dependency_sorter = MigrationDependencySorter.new
  database_migrations.each do |schema_name, schema_migrations|
    if schema_migrations[:schema_migration]
      # the schema migration never has any dependencies
      dependency_sorter[schema_migrations[:schema_migration]] = []
    end
    # add each table migration, and its dependencies
    schema_migrations[:table_migrations].values.each do |table_migration|
      deps = dependency_sorter[table_migration] = []
      # if there is a schema migration, then it should always come first
      # so make the table migration depend on it
      deps << schema_migrations[:schema_migration] if schema_migrations[:schema_migration]
      # if the table migration has any dependencies on other tables, then add them
      table_migration.table_dependencies.each do |dependency|
        # find the migration which matches the dependency
        dependent_migration = database_migrations[dependency[:schema_name]] && database_migrations[dependency[:schema_name]][:table_migrations][dependency[:table_name]]
        # if the table migration is not found, then it's safe to assume the table was created
        # by an earlier set of migrations
        unless dependent_migration.nil?
          # add the dependent migration to the list of dependencies
          deps << dependent_migration
        end
      end
      # if the table migration has any dependencies on functions or enums, then add them
      (table_migration.function_dependencies + table_migration.enum_dependencies).each do |dependency|
        # functions are always added to a schema specific migration, if it does not exist then
        # we can assume the function was added in a previous set of migrations
        if (dependencies_schema_migration = database_migrations[dependency[:schema_name]] && database_migrations[dependency[:schema_name]][:schema_migration])
          deps << dependencies_schema_migration
        end
      end
    end
    # add each additional migration, and its dependencies
    schema_migrations[:additional_migrations].each do |additional_migration|
      deps = dependency_sorter[additional_migration] = []
      # if there is a schema migration, then it should always come first
      # so make the table migration depend on it
      deps << schema_migrations[:schema_migration] if schema_migrations[:schema_migration]

      # additional migrations are always dependent on the table migration which they came from
      table_migration = schema_migrations[:table_migrations][additional_migration.table_name]
      # if the table migration is not found, then it's safe to assume the table was created
      # by an earlier set of migrations
      unless table_migration.nil?
        deps << table_migration

        # if the table migration has any dependencies on functions or enums, then add them
        (table_migration.function_dependencies + table_migration.enum_dependencies).each do |dependency|
          # functions are always added to a schema specific migration, if it does not exist then
          # we can assume the function was added in a previous set of migrations
          if (dependencies_schema_migration = database_migrations[dependency[:schema_name]] && database_migrations[dependency[:schema_name]][:schema_migration])
            deps << dependencies_schema_migration
          end
        end
      end

      # if the additional_migration has any dependencies on other tables, then add them too
      additional_migration.table_dependencies.each do |dependency|
        # find the table migration which matches the dependency
        dependent_migration = database_migrations[dependency[:schema_name]] && database_migrations[dependency[:schema_name]][:table_migrations][dependency[:table_name]]
        # if the table migration is not found, then it's safe to assume the table was created
        # by an earlier set of migrations
        unless dependent_migration.nil?
          deps << dependent_migration
        end
      end
    end
  end

  # sort the migrations so that they are executed in the correct order
  # the order is determined by their dependencies
  log.info "  Sorting migrations based on their dependencies"
  final_migrations = dependency_sorter.tsort

  # if any database only migrations exist, then add them to the front of the array here
  if database_specific_migrations.any?
    final_migrations = database_specific_migrations + final_migrations
  end

  # return the final migrations in the expected format
  final_migrations.map do |migration|
    {
      schema_name: migration.schema_name,
      name: migration.name,
      content: migration.content
    }
  end
end