text: import re
  from collections import defaultdict, namedtuple
  
  from packaging.version import Version
  import pkg_resources
  import sqlalchemy as sa
  from sqlalchemy import inspect
  from sqlalchemy.dialects.postgresql.base import (
      PGCompiler, PGDDLCompiler, PGIdentifierPreparer, PGTypeCompiler,
      PGExecutionContext, PGDialect
  )
  from sqlalchemy.dialects.postgresql.psycopg2 import PGDialect_psycopg2
  from sqlalchemy.dialects.postgresql.psycopg2cffi import PGDialect_psycopg2cffi
  from sqlalchemy.engine.default import DefaultDialect
  from sqlalchemy.sql.type_api import TypeEngine
  from sqlalchemy.engine import reflection
  from sqlalchemy.ext.compiler import compiles
  from sqlalchemy.sql.expression import (
      BinaryExpression, BooleanClauseList, Delete
  )
  from sqlalchemy.types import (
      VARCHAR, NullType, SMALLINT, INTEGER, BIGINT,
      DECIMAL, REAL, BOOLEAN, CHAR, DATE, TIMESTAMP)
  from sqlalchemy.dialects.postgresql import DOUBLE_PRECISION
  
  from .commands import (
      CopyCommand, UnloadFromSelect, Format, Compression, Encoding,
      CreateLibraryCommand, AlterTableAppendCommand, RefreshMaterializedView
  )
  from .ddl import (
      CreateMaterializedView, DropMaterializedView, get_table_attributes
  )
  import importlib
  import json
  
  sa_version = Version(sa.__version__)
  
  try:
      import alembic
  except ImportError:
      pass
  else:
      from alembic.ddl import postgresql
  
      from alembic.ddl.base import RenameTable
      compiles(RenameTable, 'redshift')(postgresql.visit_rename_table)
  
      if Version(alembic.__version__) >= Version('1.0.6'):
          from alembic.ddl.base import ColumnComment
          compiles(ColumnComment, 'redshift')(postgresql.visit_column_comment)
  
      class RedshiftImpl(postgresql.PostgresqlImpl):
          __dialect__ = 'redshift'
  
  # "Each dialect provides the full set of typenames supported by that backend
  # with its __all__ collection
  # https://docs.sqlalchemy.org/en/13/core/type_basics.html#vendor-specific-types
  __all__ = (
      'SMALLINT',
      'INTEGER',
      'BIGINT',
      'DECIMAL',
      'REAL',
      'BOOLEAN',
      'CHAR',
      'DATE',
      'TIMESTAMP',
      'VARCHAR',
      'DOUBLE_PRECISION',
      'GEOMETRY',
      'SUPER',
      'TIMESTAMPTZ',
      'TIMETZ',
      'HLLSKETCH',
  
      'RedshiftDialect', 'RedshiftDialect_psycopg2',
      'RedshiftDialect_psycopg2cffi', 'RedshiftDialect_redshift_connector',
  
      'CopyCommand', 'UnloadFromSelect', 'Compression',
      'Encoding', 'Format', 'CreateLibraryCommand', 'AlterTableAppendCommand',
      'RefreshMaterializedView',
  
      'CreateMaterializedView', 'DropMaterializedView'
  )
  
  
  # Regex for parsing and identity constraint out of adsrc, e.g.:
  #   "identity"(445178, 0, '1,1'::text)
  IDENTITY_RE = re.compile(r"""
      "identity" \(
        (?P<current>-?\d+)
        ,\s
        (?P<base>-?\d+)
        ,\s
        '(?P<seed>-?\d+),(?P<step>-?\d+)'
        .*
      \)
  """, re.VERBOSE)
  
  # Regex for SQL identifiers (valid table and column names)
  SQL_IDENTIFIER_RE = re.compile(r"""
     [_a-zA-Z][\w$]*  # SQL standard identifier
     |                # or
     (?:"[^"]+")+     # SQL delimited (quoted) identifier
  """, re.VERBOSE)
  
  # Regex for foreign key constraints, e.g.:
  #   FOREIGN KEY(col1) REFERENCES othertable (col2)
  # See https://docs.aws.amazon.com/redshift/latest/dg/r_names.html
  # for a definition of valid SQL identifiers.
  FOREIGN_KEY_RE = re.compile(r"""
    ^FOREIGN\ KEY \s* \(   # FOREIGN KEY, arbitrary whitespace, literal '('
      (?P<columns>         # Start a group to capture the referring columns
        (?:                # Start a non-capturing group
          \s*              # Arbitrary whitespace
          ([_a-zA-Z][\w$]* | ("[^"]+")+)   # SQL identifier
          \s*              # Arbitrary whitespace
          ,?               # There will be a colon if this isn't the last one
        )+                 # Close the non-capturing group; require at least one
      )                    # Close the 'columns' group
    \s* \)                 # Arbitrary whitespace and literal ')'
    \s* REFERENCES \s*
      ((?P<referred_schema>([_a-zA-Z][\w$]* | ("[^"]*")+))\.)? # SQL identifier
      (?P<referred_table>[_a-zA-Z][\w$]* | ("[^"]*")+)         # SQL identifier
    \s* \(   # FOREIGN KEY, arbitrary whitespace, literal '('
      (?P<referred_columns> # Start a group to capture the referring columns
        (?:                # Start a non-capturing group
          \s*              # Arbitrary whitespace
          ([_a-zA-Z][\w$]* | ("[^"]+")+)   # SQL identifier
          \s*              # Arbitrary whitespace
          ,?               # There will be a colon if this isn't the last one
        )+                 # Close the non-capturing group; require at least one
      )                    # Close the 'columns' group
    \s* \)                 # Arbitrary whitespace and literal ')'
  """, re.VERBOSE)
  
  # Regex for primary key constraints, e.g.:
  #   PRIMARY KEY (col1, col2)
  PRIMARY_KEY_RE = re.compile(r"""
    ^PRIMARY \s* KEY \s* \(  # FOREIGN KEY, arbitrary whitespace, literal '('
      (?P<columns>         # Start a group to capture column names
        (?:
          \s*                # Arbitrary whitespace
          # SQL identifier or delimited identifier
          ( [_a-zA-Z][\w$]* | ("[^"]*")+ )
          \s*                # Arbitrary whitespace
          ,?                 # There will be a colon if this isn't the last one
        )+                  # Close the non-capturing group; require at least one
      )
    \s* \) \s*                # Arbitrary whitespace and literal ')'
  """, re.VERBOSE)
  
  # Reserved words as extracted from Redshift docs.
  # See pull_reserved_words.sh at the top level of this repository
  # for the code used to generate this set.
  RESERVED_WORDS = set([
      "aes128", "aes256", "all", "allowoverwrite", "analyse", "analyze",
      "and", "any", "array", "as", "asc", "authorization", "az64",
      "backup", "between", "binary", "blanksasnull", "both", "bytedict",
      "bzip2", "case", "cast", "check", "collate", "column", "constraint",
      "create", "credentials", "cross", "current_date", "current_time",
      "current_timestamp", "current_user", "current_user_id", "default",
      "deferrable", "deflate", "defrag", "delta", "delta32k", "desc",
      "disable", "distinct", "do", "else", "emptyasnull", "enable",
      "encode", "encrypt", "encryption", "end", "except", "explicit",
      "false", "for", "foreign", "freeze", "from", "full", "globaldict256",
      "globaldict64k", "grant", "group", "gzip", "having", "identity",
      "ignore", "ilike", "in", "initially", "inner", "intersect", "into",
      "is", "isnull", "join", "language", "leading", "left", "like",
      "limit", "localtime", "localtimestamp", "lun", "luns", "lzo", "lzop",
      "minus", "mostly16", "mostly32", "mostly8", "natural", "new", "not",
      "notnull", "null", "nulls", "off", "offline", "offset", "oid", "old",
      "on", "only", "open", "or", "order", "outer", "overlaps", "parallel",
      "partition", "percent", "permissions", "pivot", "placing", "primary",
      "raw", "readratio", "recover", "references", "respect", "rejectlog",
      "resort", "restore", "right", "select", "session_user", "similar",
      "snapshot", "some", "sysdate", "system", "table", "tag", "tdes",
      "text255", "text32k", "then", "timestamp", "to", "top", "trailing",
      "true", "truncatecolumns", "union", "unique", "unnest", "unpivot",
      "user", "using", "verbose", "wallet", "when", "where", "with",
      "without",
  ])
  
  
  class RedshiftTypeEngine(TypeEngine):
  
      def _default_dialect(self, default=None):
          """
          Returns the default dialect used for TypeEngine compilation yielding
          String result.
  
          :meth:`~sqlalchemy.sql.type_api.TypeEngine.compile`
          """
          return RedshiftDialectMixin()
  
  
  class TIMESTAMPTZ(RedshiftTypeEngine, sa.dialects.postgresql.TIMESTAMP):
      """
      Redshift defines a TIMTESTAMPTZ column type as an alias
      of TIMESTAMP WITH TIME ZONE.
      https://docs.aws.amazon.com/redshift/latest/dg/c_Supported_data_types.html
  
      Adding an explicit type to the RedshiftDialect allows us follow the
      SqlAlchemy conventions for "vendor-specific types."
  
      https://docs.sqlalchemy.org/en/13/core/type_basics.html#vendor-specific-types
      """
  
      __visit_name__ = 'TIMESTAMPTZ'
  
      def __init__(self, timezone=True, precision=None):
          # timezone param must be present as it's provided in base class so the
          # object can be instantiated with kwargs. see
          # :meth:`~sqlalchemy.dialects.postgresql.base.PGDialect._get_column_info`
          super(TIMESTAMPTZ, self).__init__(timezone=True, precision=precision)
  
  
  class TIMETZ(RedshiftTypeEngine, sa.dialects.postgresql.TIME):
      """
      Redshift defines a TIMTETZ column type as an alias
      of TIME WITH TIME ZONE.
      https://docs.aws.amazon.com/redshift/latest/dg/c_Supported_data_types.html
  
      Adding an explicit type to the RedshiftDialect allows us follow the
      SqlAlchemy conventions for "vendor-specific types."
  
      https://docs.sqlalchemy.org/en/13/core/type_basics.html#vendor-specific-types
      """
  
      __visit_name__ = 'TIMETZ'
  
      def __init__(self, timezone=True, precision=None):
          # timezone param must be present as it's provided in base class so the
          # object can be instantiated with kwargs. see
          # :meth:`~sqlalchemy.dialects.postgresql.base.PGDialect._get_column_info`
          super(TIMETZ, self).__init__(timezone=True, precision=precision)
  
  
  class GEOMETRY(RedshiftTypeEngine, sa.dialects.postgresql.TEXT):
      """
      Redshift defines a GEOMETRY column type
      https://docs.aws.amazon.com/redshift/latest/dg/c_Supported_data_types.html
  
      Adding an explicit type to the RedshiftDialect allows us follow the
      SqlAlchemy conventions for "vendor-specific types."
  
      https://docs.sqlalchemy.org/en/13/core/type_basics.html#vendor-specific-types
      """
      __visit_name__ = 'GEOMETRY'
  
      def __init__(self):
          super(GEOMETRY, self).__init__()
  
      def get_dbapi_type(self, dbapi):
          return dbapi.GEOMETRY
  
  
  class SUPER(RedshiftTypeEngine, sa.dialects.postgresql.TEXT):
      """
      Redshift defines a SUPER column type
      https://docs.aws.amazon.com/redshift/latest/dg/c_Supported_data_types.html
  
      Adding an explicit type to the RedshiftDialect allows us follow the
      SqlAlchemy conventions for "vendor-specific types."
  
      https://docs.sqlalchemy.org/en/13/core/type_basics.html#vendor-specific-types
      """
  
      __visit_name__ = 'SUPER'
  
      def __init__(self):
          super(SUPER, self).__init__()
  
      def get_dbapi_type(self, dbapi):
          return dbapi.SUPER
  
      def bind_expression(self, bindvalue):
          return sa.func.json_parse(bindvalue)
  
      def process_bind_param(self, value, dialect):
          if not isinstance(value, str):
              return json.dumps(value)
          return value
  
  
  class HLLSKETCH(RedshiftTypeEngine, sa.dialects.postgresql.TEXT):
      """
      Redshift defines a HLLSKETCH column type
      https://docs.aws.amazon.com/redshift/latest/dg/c_Supported_data_types.html
  
      Adding an explicit type to the RedshiftDialect allows us follow the
      SqlAlchemy conventions for "vendor-specific types."
  
      https://docs.sqlalchemy.org/en/13/core/type_basics.html#vendor-specific-types
      """
      __visit_name__ = 'HLLSKETCH'
  
      def __init__(self):
          super(HLLSKETCH, self).__init__()
  
      def get_dbapi_type(self, dbapi):
          return dbapi.HLLSKETCH
  
  
  # Mapping for database schema inspection of Amazon Redshift datatypes
  REDSHIFT_ISCHEMA_NAMES = {
      "geometry": GEOMETRY,
      "super": SUPER,
      "time with time zone": TIMETZ,
      "timestamp with time zone": TIMESTAMPTZ,
      "hllsketch": HLLSKETCH,
  }
  
  
  class RelationKey(namedtuple('RelationKey', ('name', 'schema'))):
      """
      Structured tuple of table/view name and schema name.
      """
      __slots__ = ()
  
      def __new__(cls, name, schema=None, connection=None):
          """
          Construct a new RelationKey with an explicit schema name.
          """
          if schema is None and connection is None:
              raise ValueError("Must specify either schema or connection")
          if schema is None:
              schema = inspect(connection).default_schema_name
          return super(RelationKey, cls).__new__(cls, name, schema)
  
      def __str__(self):
          if self.schema is None:
              return self.name
          else:
              return self.schema + "." + self.name
  
      @staticmethod
      def _unquote(part):
          if (
                  part is not None and part.startswith('"') and
                  part.endswith('"')
          ):
              return part[1:-1]
          return part
  
      def unquoted(self):
          """
          Return *key* with one level of double quotes removed.
  
          Redshift stores some identifiers without quotes in internal tables,
          even though the name must be quoted elsewhere.
          In particular, this happens for tables named as a keyword.
          """
          return RelationKey(
              RelationKey._unquote(self.name),
              RelationKey._unquote(self.schema)
          )
  
  
  class RedshiftCompiler(PGCompiler):
  
      def visit_now_func(self, fn, **kw):
          return "SYSDATE"
  
  
  class RedshiftDDLCompiler(PGDDLCompiler):
      """
      Handles Redshift-specific ``CREATE TABLE`` syntax.
  
      Users can specify the `diststyle`, `distkey`, `sortkey` and `encode`
      properties per table and per column.
  
      Table level properties can be set using the dialect specific syntax. For
      example, to specify a distribution key and style you apply the following:
  
      >>> import sqlalchemy as sa
      >>> from sqlalchemy.schema import CreateTable
      >>> engine = sa.create_engine('redshift+psycopg2://example')
      >>> metadata = sa.MetaData()
      >>> user = sa.Table(
      ...     'user',
      ...     metadata,
      ...     sa.Column('id', sa.Integer, primary_key=True),
      ...     sa.Column('name', sa.String),
      ...     redshift_diststyle='KEY',
      ...     redshift_distkey='id',
      ...     redshift_interleaved_sortkey=['id', 'name'],
      ... )
      >>> print(CreateTable(user).compile(engine))
      <BLANKLINE>
      CREATE TABLE "user" (
          id INTEGER NOT NULL,
          name VARCHAR,
          PRIMARY KEY (id)
      ) DISTSTYLE KEY DISTKEY (id) INTERLEAVED SORTKEY (id, name)
      <BLANKLINE>
      <BLANKLINE>
  
      A single sort key can be applied without a wrapping list:
  
      >>> customer = sa.Table(
      ...     'customer',
      ...     metadata,
      ...     sa.Column('id', sa.Integer, primary_key=True),
      ...     sa.Column('name', sa.String),
      ...     redshift_sortkey='id',
      ... )
      >>> print(CreateTable(customer).compile(engine))
      <BLANKLINE>
      CREATE TABLE customer (
          id INTEGER NOT NULL,
          name VARCHAR,
          PRIMARY KEY (id)
      ) SORTKEY (id)
      <BLANKLINE>
      <BLANKLINE>
  
      Column-level special syntax can also be applied using Redshift dialect
      specific keyword arguments.
      For example, we can specify the ENCODE for a column:
  
      >>> product = sa.Table(
      ...     'product',
      ...     metadata,
      ...     sa.Column('id', sa.Integer, primary_key=True),
      ...     sa.Column('name', sa.String, redshift_encode='lzo')
      ... )
      >>> print(CreateTable(product).compile(engine))
      <BLANKLINE>
      CREATE TABLE product (
          id INTEGER NOT NULL,
          name VARCHAR ENCODE lzo,
          PRIMARY KEY (id)
      )
      <BLANKLINE>
      <BLANKLINE>
  
      The TIMESTAMPTZ and TIMETZ column types are also supported in the DDL.
  
      For SQLAlchemy versions < 1.3.0, passing Redshift dialect options
      as keyword arguments is not supported on the column level.
      Instead, a column info dictionary can be used:
  
      >>> product_pre_1_3_0 = sa.Table(
      ...     'product_pre_1_3_0',
      ...     metadata,
      ...     sa.Column('id', sa.Integer, primary_key=True),
      ...     sa.Column('name', sa.String, info={'encode': 'lzo'})
      ... )
  
      We can also specify the distkey and sortkey options:
  
      >>> sku = sa.Table(
      ...     'sku',
      ...     metadata,
      ...     sa.Column('id', sa.Integer, primary_key=True),
      ...     sa.Column(
      ...         'name',
      ...         sa.String,
      ...         redshift_distkey=True,
      ...         redshift_sortkey=True
      ...     )
      ... )
      >>> print(CreateTable(sku).compile(engine))
      <BLANKLINE>
      CREATE TABLE sku (
          id INTEGER NOT NULL,
          name VARCHAR DISTKEY SORTKEY,
          PRIMARY KEY (id)
      )
      <BLANKLINE>
      <BLANKLINE>
      """
  
      def post_create_table(self, table):
          kwargs = ["diststyle", "distkey", "sortkey", "interleaved_sortkey"]
          info = table.dialect_options['redshift']
          info = {key: info.get(key) for key in kwargs}
          return get_table_attributes(self.preparer, **info)
  
      def get_column_specification(self, column, **kwargs):
          colspec = self.preparer.format_column(column)
  
          colspec += " " + self.dialect.type_compiler.process(column.type)
  
          default = self.get_column_default_string(column)
          if default is not None:
              # Identity constraints show up as *default* when reflected.
              m = IDENTITY_RE.match(default)
              if m:
                  colspec += " IDENTITY({seed},{step})".format(**m.groupdict())
              else:
                  colspec += " DEFAULT " + default
  
          colspec += self._fetch_redshift_column_attributes(column)
  
          if not column.nullable:
              colspec += " NOT NULL"
          return colspec
  
      def _fetch_redshift_column_attributes(self, column):
          text = ""
          if sa_version >= Version('1.3.0'):
              info = column.dialect_options['redshift']
          else:
              if not hasattr(column, 'info'):
                  return text
              info = column.info
  
          identity = info.get('identity')
          if identity:
              text += " IDENTITY({0},{1})".format(identity[0], identity[1])
  
          encode = info.get('encode')
          if encode:
              text += " ENCODE " + encode
  
          distkey = info.get('distkey')
          if distkey:
              text += " DISTKEY"
  
          sortkey = info.get('sortkey')
          if sortkey:
              text += " SORTKEY"
          return text
  
  
  class RedshiftTypeCompiler(PGTypeCompiler):
  
      def visit_GEOMETRY(self, type_, **kw):
          return "GEOMETRY"
  
      def visit_SUPER(self, type_, **kw):
          return "SUPER"
  
      def visit_TIMESTAMPTZ(self, type_, **kw):
          return "TIMESTAMPTZ"
  
      def visit_TIMETZ(self, type_, **kw):
          return "TIMETZ"
  
      def visit_HLLSKETCH(self, type_, **kw):
          return "HLLSKETCH"
  
  
  class RedshiftIdentifierPreparer(PGIdentifierPreparer):
      reserved_words = RESERVED_WORDS
  
  
  class RedshiftDialectMixin(DefaultDialect):
      """
      Define Redshift-specific behavior.
  
      Most public methods are overrides of the underlying interfaces defined in
      :class:`~sqlalchemy.engine.interfaces.Dialect` and
      :class:`~sqlalchemy.engine.Inspector`.
      """
  
      name = 'redshift'
      max_identifier_length = 127
      # explicitly disables statement cache to disable warnings in logs
      # ref: https://docs.sqlalchemy.org/en/14/core/connections.html#caching-for-third-party-dialects  # noqa
      supports_statement_cache = False
  
      statement_compiler = RedshiftCompiler
      ddl_compiler = RedshiftDDLCompiler
      preparer = RedshiftIdentifierPreparer
      type_compiler = RedshiftTypeCompiler
      construct_arguments = [
          (sa.schema.Index, {
              "using": False,
              "where": None,
              "ops": {}
          }),
          (sa.schema.Table, {
              "ignore_search_path": False,
              "diststyle": None,
              "distkey": None,
              "sortkey": None,
              "interleaved_sortkey": None,
          }),
          (sa.schema.Column, {
              "encode": None,
              "distkey": None,
              "sortkey": None,
              "identity": None,
          }),
      ]
  
      def __init__(self, *args, **kw):
          super(RedshiftDialectMixin, self).__init__(*args, **kw)
          # Cache domains, as these will be static;
          # Redshift does not support user-created domains.
          self._domains = None
  
      @property
      def ischema_names(self):
          """
          Returns information about datatypes supported by Amazon Redshift.
  
          Used in
          :meth:`~sqlalchemy.engine.dialects.postgresql.base.PGDialect._get_column_info`.
          """
          return {
              **super(RedshiftDialectMixin, self).ischema_names,
              **REDSHIFT_ISCHEMA_NAMES
          }
  
      @reflection.cache
      def get_columns(self, connection, table_name, schema=None, **kw):
          """
          Return information about columns in `table_name`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_columns`.
          """
          cols = self._get_redshift_columns(connection, table_name, schema, **kw)
          if not self._domains:
              self._domains = self._load_domains(connection)
          domains = self._domains
          columns = []
          for col in cols:
              column_info = self._get_column_info(
                  name=col.name, format_type=col.format_type,
                  default=col.default, notnull=col.notnull, domains=domains,
                  enums=[], schema=col.schema, encode=col.encode,
                  comment=col.comment)
              columns.append(column_info)
          return columns
  
      @reflection.cache
      def get_pk_constraint(self, connection, table_name, schema=None, **kw):
          """
          Return information about the primary key constraint on `table_name`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_pk_constraint`.
          """
          constraints = self._get_redshift_constraints(connection, table_name,
                                                       schema, **kw)
          pk_constraints = [c for c in constraints if c.contype == 'p']
          if not pk_constraints:
              return {'constrained_columns': [], 'name': ''}
          pk_constraint = pk_constraints[0]
          m = PRIMARY_KEY_RE.match(pk_constraint.condef)
          colstring = m.group('columns')
          constrained_columns = SQL_IDENTIFIER_RE.findall(colstring)
          return {
              'constrained_columns': constrained_columns,
              'name': pk_constraint.conname,
          }
  
      @reflection.cache
      def get_foreign_keys(self, connection, table_name, schema=None, **kw):
          """
          Return information about foreign keys in `table_name`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_pk_constraint`.
          """
          constraints = self._get_redshift_constraints(connection, table_name,
                                                       schema, **kw)
          fk_constraints = [c for c in constraints if c.contype == 'f']
          uniques = defaultdict(lambda: defaultdict(dict))
          for con in fk_constraints:
              uniques[con.conname]["key"] = con.conkey
              uniques[con.conname]["condef"] = con.condef
          fkeys = []
          for conname, attrs in uniques.items():
              m = FOREIGN_KEY_RE.match(attrs['condef'])
              colstring = m.group('referred_columns')
              referred_columns = SQL_IDENTIFIER_RE.findall(colstring)
              referred_table = m.group('referred_table')
              referred_schema = m.group('referred_schema')
              colstring = m.group('columns')
              constrained_columns = SQL_IDENTIFIER_RE.findall(colstring)
              fkey_d = {
                  'name': conname,
                  'constrained_columns': constrained_columns,
                  'referred_schema': referred_schema,
                  'referred_table': referred_table,
                  'referred_columns': referred_columns,
              }
              fkeys.append(fkey_d)
          return fkeys
  
      @reflection.cache
      def get_table_names(self, connection, schema=None, **kw):
          """
          Return a list of table names for `schema`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_table_names`.
          """
          return self._get_table_or_view_names('r', connection, schema, **kw)
  
      @reflection.cache
      def get_view_names(self, connection, schema=None, **kw):
          """
          Return a list of view names for `schema`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_view_names`.
          """
          return self._get_table_or_view_names('v', connection, schema, **kw)
  
      @reflection.cache
      def get_view_definition(self, connection, view_name, schema=None, **kw):
          """Return view definition.
          Given a :class:`.Connection`, a string `view_name`,
          and an optional string `schema`, return the view definition.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_view_definition`.
          """
          view = self._get_redshift_relation(connection, view_name, schema, **kw)
          return sa.text(view.view_definition)
  
      def get_indexes(self, connection, table_name, schema, **kw):
          """
          Return information about indexes in `table_name`.
  
          Because Redshift does not support traditional indexes,
          this always returns an empty list.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_indexes`.
          """
          return []
  
      @reflection.cache
      def get_unique_constraints(self, connection, table_name,
                                 schema=None, **kw):
          """
          Return information about unique constraints in `table_name`.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.get_unique_constraints`.
          """
          constraints = self._get_redshift_constraints(connection,
                                                       table_name, schema, **kw)
          constraints = [c for c in constraints if c.contype == 'u']
          uniques = defaultdict(lambda: defaultdict(dict))
          for con in constraints:
              uniques[con.conname]["key"] = con.conkey
              uniques[con.conname]["cols"][con.attnum] = con.attname
  
          return [
              {'name': name,
               'column_names': [uc["cols"][i] for i in uc["key"]]}
              for name, uc in uniques.items()
          ]
  
      @reflection.cache
      def get_table_options(self, connection, table_name, schema, **kw):
          """
          Return a dictionary of options specified when the table of the
          given name was created.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.Inspector.get_table_options`.
          """
          def keyfunc(column):
              num = int(column.sortkey)
              # If sortkey is interleaved, column numbers alternate
              # negative values, so take abs.
              return abs(num)
          table = self._get_redshift_relation(connection, table_name,
                                              schema, **kw)
          columns = self._get_redshift_columns(connection, table_name,
                                               schema, **kw)
          sortkey_cols = sorted([col for col in columns if col.sortkey],
                                key=keyfunc)
          interleaved = any([int(col.sortkey) < 0 for col in sortkey_cols])
          sortkey = tuple(col.name for col in sortkey_cols)
          interleaved_sortkey = None
          if interleaved:
              interleaved_sortkey = sortkey
              sortkey = None
          distkeys = [col.name for col in columns if col.distkey]
          distkey = distkeys[0] if distkeys else None
          return {
              'redshift_diststyle': table.diststyle,
              'redshift_distkey': distkey,
              'redshift_sortkey': sortkey,
              'redshift_interleaved_sortkey': interleaved_sortkey,
          }
  
      def _get_table_or_view_names(self, relkind, connection, schema=None, **kw):
          default_schema = inspect(connection).default_schema_name
          if not schema:
              schema = default_schema
          info_cache = kw.get('info_cache')
          all_relations = self._get_all_relation_info(connection,
                                                      info_cache=info_cache)
          relation_names = []
          for key, relation in all_relations.items():
              if key.schema == schema and relation.relkind == relkind:
                  relation_names.append(key.name)
          return relation_names
  
      def _get_column_info(self, *args, **kwargs):
          kw = kwargs.copy()
          encode = kw.pop('encode', None)
          if sa_version >= Version('1.3.16'):
              # SQLAlchemy 1.3.16 introduced generated columns,
              # not supported in redshift
              kw['generated'] = ''
  
          if sa_version < Version('1.4.0') and 'identity' in kw:
              del kw['identity']
          elif sa_version >= Version('1.4.0') and 'identity' not in kw:
              kw['identity'] = None
  
          column_info = super(RedshiftDialectMixin, self)._get_column_info(
              *args,
              **kw
          )
          if isinstance(column_info['type'], VARCHAR):
              if column_info['type'].length is None:
                  column_info['type'] = NullType()
          if 'info' not in column_info:
              column_info['info'] = {}
          if encode and encode != 'none':
              column_info['info']['encode'] = encode
          return column_info
  
      def _get_redshift_relation(self, connection, table_name,
                                 schema=None, **kw):
          info_cache = kw.get('info_cache')
          all_relations = self._get_all_relation_info(connection,
                                                      info_cache=info_cache)
          key = RelationKey(table_name, schema, connection)
          if key not in all_relations.keys():
              key = key.unquoted()
          try:
              return all_relations[key]
          except KeyError:
              raise sa.exc.NoSuchTableError(key)
  
      def _get_redshift_columns(self, connection, table_name, schema=None, **kw):
          info_cache = kw.get('info_cache')
          all_schema_columns = self._get_schema_column_info(
              connection,
              schema,
              info_cache=info_cache
          )
          key = RelationKey(table_name, schema, connection)
          if key not in all_schema_columns.keys():
              key = key.unquoted()
          return all_schema_columns[key]
  
      def _get_redshift_constraints(self, connection, table_name,
                                    schema=None, **kw):
          info_cache = kw.get('info_cache')
          all_constraints = self._get_all_constraint_info(connection,
                                                          info_cache=info_cache)
          key = RelationKey(table_name, schema, connection)
          if key not in all_constraints.keys():
              key = key.unquoted()
          return all_constraints[key]
  
      @reflection.cache
      def _get_all_relation_info(self, connection, **kw):
          result = connection.execute(sa.text("""
          SELECT
            c.relkind,
            n.oid as "schema_oid",
            n.nspname as "schema",
            c.oid as "rel_oid",
            c.relname,
            CASE c.reldiststyle
              WHEN 0 THEN 'EVEN' WHEN 1 THEN 'KEY' WHEN 8 THEN 'ALL' END
              AS "diststyle",
            c.relowner AS "owner_id",
            u.usename AS "owner_name",
            TRIM(TRAILING ';' FROM pg_catalog.pg_get_viewdef(c.oid, true))
              AS "view_definition",
            pg_catalog.array_to_string(c.relacl, '\n') AS "privileges"
          FROM pg_catalog.pg_class c
               LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
               JOIN pg_catalog.pg_user u ON u.usesysid = c.relowner
          WHERE c.relkind IN ('r', 'v', 'm', 'S', 'f')
            AND n.nspname !~ '^pg_'
          ORDER BY c.relkind, n.oid, n.nspname;
          """))
          relations = {}
          for rel in result:
              key = RelationKey(rel.relname, rel.schema, connection)
              relations[key] = rel
          return relations
  
      # We fetch column info an entire schema at a time to improve performance
      # when reflecting schema for multiple tables at once.
      @reflection.cache
      def _get_schema_column_info(
          self, connection, schema=None, **kw
      ):
          schema_clause = (
              "AND schema = '{schema}'".format(schema=schema) if schema else ""
          )
          all_columns = defaultdict(list)
          result = connection.execute(sa.text("""
          SELECT
            n.nspname as "schema",
            c.relname as "table_name",
            att.attname as "name",
            format_encoding(att.attencodingtype::integer) as "encode",
            format_type(att.atttypid, att.atttypmod) as "type",
            att.attisdistkey as "distkey",
            att.attsortkeyord as "sortkey",
            att.attnotnull as "notnull",
            pg_catalog.col_description(att.attrelid, att.attnum)
              as "comment",
            adsrc,
            attnum,
            pg_catalog.format_type(att.atttypid, att.atttypmod),
            pg_catalog.pg_get_expr(ad.adbin, ad.adrelid) AS DEFAULT,
            n.oid as "schema_oid",
            c.oid as "table_oid"
          FROM pg_catalog.pg_class c
          LEFT JOIN pg_catalog.pg_namespace n
            ON n.oid = c.relnamespace
          JOIN pg_catalog.pg_attribute att
            ON att.attrelid = c.oid
          LEFT JOIN pg_catalog.pg_attrdef ad
            ON (att.attrelid, att.attnum) = (ad.adrelid, ad.adnum)
          WHERE n.nspname !~ '^pg_'
            AND att.attnum > 0
            AND NOT att.attisdropped
            {schema_clause}
          UNION
          SELECT
            view_schema as "schema",
            view_name as "table_name",
            col_name as "name",
            null as "encode",
            col_type as "type",
            null as "distkey",
            0 as "sortkey",
            null as "notnull",
            null as "comment",
            null as "adsrc",
            null as "attnum",
            col_type as "format_type",
            null as "default",
            null as "schema_oid",
            null as "table_oid"
          FROM pg_get_late_binding_view_cols() cols(
            view_schema name,
            view_name name,
            col_name name,
            col_type varchar,
            col_num int)
          WHERE 1 {schema_clause}
          ORDER BY "schema", "table_name", "attnum";
          """.format(schema_clause=schema_clause))
          )
          for col in result:
              key = RelationKey(col.table_name, col.schema, connection)
              all_columns[key].append(col)
  
          return dict(all_columns)
  
      @reflection.cache
      def _get_all_constraint_info(self, connection, **kw):
          result = connection.execute(sa.text("""
          SELECT
            n.nspname as "schema",
            c.relname as "table_name",
            t.contype,
            t.conname,
            t.conkey,
            a.attnum,
            a.attname,
            pg_catalog.pg_get_constraintdef(t.oid, true) as condef,
            n.oid as "schema_oid",
            c.oid as "rel_oid"
          FROM pg_catalog.pg_class c
          LEFT JOIN pg_catalog.pg_namespace n
            ON n.oid = c.relnamespace
          JOIN pg_catalog.pg_constraint t
            ON t.conrelid = c.oid
          JOIN pg_catalog.pg_attribute a
            ON t.conrelid = a.attrelid AND a.attnum = ANY(t.conkey)
          WHERE n.nspname !~ '^pg_'
          ORDER BY n.nspname, c.relname
          """))
          all_constraints = defaultdict(list)
          for con in result:
              key = RelationKey(con.table_name, con.schema, connection)
              all_constraints[key].append(con)
          return all_constraints
  
  
  class Psycopg2RedshiftDialectMixin(RedshiftDialectMixin):
      """
      Define behavior specific to ``psycopg2``.
  
      Most public methods are overrides of the underlying interfaces defined in
      :class:`~sqlalchemy.engine.interfaces.Dialect` and
      :class:`~sqlalchemy.engine.Inspector`.
      """
      def create_connect_args(self, *args, **kwargs):
          """
          Build DB-API compatible connection arguments.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.create_connect_args`.
          """
          default_args = {
              'sslmode': 'verify-full',
              'sslrootcert': pkg_resources.resource_filename(
                  __name__,
                  'redshift-ca-bundle.crt'
              ),
          }
          cargs, cparams = (
              super(Psycopg2RedshiftDialectMixin, self).create_connect_args(
                  *args, **kwargs
              )
          )
          default_args.update(cparams)
          return cargs, default_args
  
      @classmethod
      def dbapi(cls):
          try:
              return importlib.import_module(cls.driver)
          except ImportError:
              raise ImportError(
                  'No module named {}'.format(cls.driver)
              )
  
  
  class RedshiftDialect_psycopg2(
      Psycopg2RedshiftDialectMixin, PGDialect_psycopg2
  ):
      pass
  
  
  # Add RedshiftDialect synonym for backwards compatibility.
  RedshiftDialect = RedshiftDialect_psycopg2
  
  
  class RedshiftDialect_psycopg2cffi(
      Psycopg2RedshiftDialectMixin, PGDialect_psycopg2cffi
  ):
      pass
  
  
  class RedshiftDialect_redshift_connector(RedshiftDialectMixin, PGDialect):
  
      class RedshiftCompiler_redshift_connector(RedshiftCompiler, PGCompiler):
          def limit_clause(self, select, **kw):
              text = ""
              if select._limit_clause is not None:
                  # an integer value for limit is retrieved
                  text += " \n LIMIT " + str(select._limit)
              if select._offset_clause is not None:
                  if select._limit_clause is None:
                      text += "\n LIMIT ALL"
                  # an integer value for offset is retrieved
                  text += " OFFSET " + str(select._offset)
              return text
  
          def visit_mod_binary(self, binary, operator, **kw):
              return (
                  self.process(binary.left, **kw)
                  + " %% "
                  + self.process(binary.right, **kw)
              )
  
          def post_process_text(self, text):
              from sqlalchemy import util
              if "%%" in text:
                  util.warn(
                      "The SQLAlchemy postgresql dialect "
                      "now automatically escapes '%' in text() "
                      "expressions to '%%'."
                  )
              return text.replace("%", "%%")
  
      class RedshiftExecutionContext_redshift_connector(PGExecutionContext):
          def pre_exec(self):
              if not self.compiled:
                  return
  
      driver = 'redshift_connector'
  
      supports_unicode_statements = True
  
      supports_unicode_binds = True
  
      default_paramstyle = "format"
      supports_sane_multi_rowcount = True
      statement_compiler = RedshiftCompiler_redshift_connector
      execution_ctx_cls = RedshiftExecutionContext_redshift_connector
      description_encoding = "use_encoding"
  
      supports_statement_cache = True
      use_setinputsizes = False  # not implemented in redshift_connector
  
      def __init__(self, client_encoding=None, **kwargs):
          super(
              RedshiftDialect_redshift_connector, self
          ).__init__(client_encoding=client_encoding, **kwargs)
          self.client_encoding = client_encoding
  
      @classmethod
      def dbapi(cls):
          try:
              return importlib.import_module(cls.driver)
          except ImportError:
              raise ImportError(
                  'No module named redshift_connector. Please install '
                  'redshift_connector to use this sqlalchemy dialect.'
              )
  
      def set_client_encoding(self, connection, client_encoding):
          """
          Sets the client-side encoding using the provided connection object.
          """
          # adjust for ConnectionFairy possibly being present
          if hasattr(connection, "connection"):
              connection = connection.connection
  
          cursor = connection.cursor()
          cursor.execute("SET CLIENT_ENCODING TO '" + client_encoding + "'")
          cursor.execute("COMMIT")
          cursor.close()
  
      def set_isolation_level(self, connection, level):
          """
          Sets the isolation level for the current transaction.
  
          Additionally, autocommit can be enabled on the underlying
          db-api connection object via argument level='AUTOCOMMIT'.
  
          See Amazon Redshift documentation for information on supported
          isolation levels.
          https://docs.aws.amazon.com/redshift/latest/dg/r_BEGIN.html
          """
          level = level.replace("_", " ")
  
          # adjust for ConnectionFairy possibly being present
          if hasattr(connection, "connection"):
              connection = connection.connection
  
          if level == "AUTOCOMMIT":
              connection.autocommit = True
          else:
              connection.autocommit = False
              super(
                  RedshiftDialect_redshift_connector, self
              ).set_isolation_level(connection, level)
  
      def on_connect(self):
          fns = []
  
          def on_connect(conn):
              from sqlalchemy.sql.elements import quoted_name
              from sqlalchemy import util
              conn.py_types[quoted_name] = conn.py_types[util.text_type]
  
          fns.append(on_connect)
  
          if self.client_encoding is not None:
  
              def on_connect(conn):
                  self.set_client_encoding(conn, self.client_encoding)
  
              fns.append(on_connect)
  
          if self.isolation_level is not None:
  
              def on_connect(conn):
                  self.set_isolation_level(conn, self.isolation_level)
  
              fns.append(on_connect)
  
          if len(fns) > 0:
  
              def on_connect(conn):
                  for fn in fns:
                      fn(conn)
  
              return on_connect
          else:
              return None
  
      def create_connect_args(self, *args, **kwargs):
          """
          Build DB-API compatible connection arguments.
  
          Overrides interface
          :meth:`~sqlalchemy.engine.interfaces.Dialect.create_connect_args`.
          """
          default_args = {
              'sslmode': 'verify-full',
              'ssl': True,
              'application_name': 'sqlalchemy-redshift'
          }
          cargs, cparams = super(RedshiftDialectMixin, self).create_connect_args(
              *args, **kwargs
          )
          # set client_encoding so it is picked up by on_connect(), as
          # redshift_connector does not have client_encoding connection parameter
          self.client_encoding = cparams.pop(
              'client_encoding', self.client_encoding
          )
  
          if 'port' in cparams:
              cparams['port'] = int(cparams['port'])
  
          if 'username' in cparams:
              cparams['user'] = cparams['username']
              del cparams['username']
  
          default_args.update(cparams)
          return cargs, default_args
  
  
  def gen_columns_from_children(root):
      """
      Generates columns that are being used in child elements of the delete query
      this will be used to determine tables for the using clause.
      :param root: the delete query
      :return: a generator of columns
      """
      if isinstance(root, (Delete, BinaryExpression, BooleanClauseList)):
          for child in root.get_children():
              yc = gen_columns_from_children(child)
              for it in yc:
                  yield it
      elif isinstance(root, sa.Column):
          yield root
  
  
  @compiles(Delete, 'redshift')
  def visit_delete_stmt(element, compiler, **kwargs):
      """
      Adds redshift-dialect specific compilation rule for the
      delete statement.
  
      Redshift DELETE syntax can be found here:
      https://docs.aws.amazon.com/redshift/latest/dg/r_DELETE.html
  
      .. :code-block: sql
  
          DELETE [ FROM ] table_name
          [ { USING } table_name, ...]
          [ WHERE condition ]
  
      By default, SqlAlchemy compiles DELETE statements with the
      syntax:
  
      .. :code-block: sql
  
          DELETE [ FROM ] table_name
          [ WHERE condition ]
  
      problem illustration:
  
      >>> from sqlalchemy import Table, Column, Integer, MetaData, delete
      >>> from sqlalchemy_redshift.dialect import RedshiftDialect_psycopg2
      >>> meta = MetaData()
      >>> table1 = Table(
      ... 'table_1',
      ... meta,
      ... Column('pk', Integer, primary_key=True)
      ... )
      ...
      >>> table2 = Table(
      ... 'table_2',
      ... meta,
      ... Column('pk', Integer, primary_key=True)
      ... )
      ...
      >>> del_stmt = delete(table1).where(table1.c.pk==table2.c.pk)
      >>> str(del_stmt.compile(dialect=RedshiftDialect_psycopg2()))
      'DELETE FROM table_1 USING table_2 WHERE table_1.pk = table_2.pk'
      >>> str(del_stmt)
      'DELETE FROM table_1 , table_2 WHERE table_1.pk = table_2.pk'
      >>> del_stmt2 = delete(table1)
      >>> str(del_stmt2)
      'DELETE FROM table_1'
      >>> del_stmt3 = delete(table1).where(table1.c.pk > 1000)
      >>> str(del_stmt3)
      'DELETE FROM table_1 WHERE table_1.pk > :pk_1'
      >>> str(del_stmt3.compile(dialect=RedshiftDialect_psycopg2()))
      'DELETE FROM table_1 WHERE table_1.pk >  %(pk_1)s'
      """
  
      # Set empty strings for the default where clause and using clause
      whereclause = ''
      usingclause = ''
  
      # determine if the delete query needs a ``USING`` injected
      # by inspecting the whereclause's children & their children...
      # first, the where clause text is buit, if applicable
      # then, the using clause text is built, if applicable
      # note:
      #   the tables in the using clause are sorted in the order in
      #   which they first appear in the where clause.
      delete_stmt_table = compiler.process(element.table, asfrom=True, **kwargs)
  
      if sa_version >= Version('1.4.0'):
          if element.whereclause is not None:
              clause = compiler.process(element.whereclause, **kwargs)
              if clause:
                  whereclause = ' WHERE {clause}'.format(clause=clause)
      else:
          whereclause_tuple = element.get_children()
          if whereclause_tuple:
              whereclause = ' WHERE {clause}'.format(
                  clause=compiler.process(*whereclause_tuple, **kwargs)
              )
  
      if whereclause:
          usingclause_tables = []
          whereclause_columns = gen_columns_from_children(element)
          for col in whereclause_columns:
              table = compiler.process(col.table, asfrom=True, **kwargs)
              if table != delete_stmt_table and \
                      table not in usingclause_tables:
                  usingclause_tables.append(table)
          if usingclause_tables:
              usingclause = ' USING {clause}'.format(
                  clause=', '.join(usingclause_tables)
              )
  
      return 'DELETE FROM {table}{using}{where}'.format(
          table=delete_stmt_table,
          using=usingclause,
          where=whereclause)
  