Method parse_fks

lib/sqlalchemy/dialects/sqlite/base.py:2659–2724

()

        table_data = self._get_table_sql(connection, table_name, schema=schema)

        def parse_fks():
            if table_data is None:
                # system tables, etc.
                return

            # note that we already have the FKs from PRAGMA above.  This whole
            # regexp thing is trying to locate additional detail about the
            # FKs, namely the name of the constraint and other options.
            # so parsing the columns is really about matching it up to what
            # we already have.
            FK_PATTERN = (
                r'(?:CONSTRAINT +(?:"(.+?)"|(\w+)) +)?'
                r"FOREIGN KEY *\( *(.+?) *\) +"
                r'REFERENCES +(?:(?:"(.+?)")|([a-z0-9_]+)) *\( *((?:(?:"[^"]+"|[a-z0-9_]+) *(?:, *)?)+)\) *'  # noqa: E501
                r"((?:ON (?:DELETE|UPDATE) "
                r"(?:SET NULL|SET DEFAULT|CASCADE|RESTRICT|NO ACTION) *)*)"
                r"((?:NOT +)?DEFERRABLE)?"
                r"(?: +INITIALLY +(DEFERRED|IMMEDIATE))?"
            )
            for match in re.finditer(FK_PATTERN, table_data, re.I):
                (
                    constraint_quoted_name,
                    constraint_name,
                    constrained_columns,
                    referred_quoted_name,
                    referred_name,
                    referred_columns,
                    onupdatedelete,
                    deferrable,
                    initially,
                ) = match.group(1, 2, 3, 4, 5, 6, 7, 8, 9)
                constraint_name = constraint_quoted_name or constraint_name
                constrained_columns = list(
                    self._find_cols_in_sig(constrained_columns)
                )
                if not referred_columns:
                    referred_columns = constrained_columns
                else:
                    referred_columns = list(
                        self._find_cols_in_sig(referred_columns)
                    )
                referred_name = referred_quoted_name or referred_name
                options = {}

                for token in re.split(r" *\bON\b *", onupdatedelete.upper()):
                    if token.startswith("DELETE"):
                        ondelete = token[6:].strip()
                        if ondelete and ondelete != "NO ACTION":
                            options["ondelete"] = ondelete
                    elif token.startswith("UPDATE"):
                        onupdate = token[6:].strip()
                        if onupdate and onupdate != "NO ACTION":
                            options["onupdate"] = onupdate

                if deferrable:
                    options["deferrable"] = "NOT" not in deferrable.upper()
                if initially:
                    options["initially"] = initially.upper()