✨ Add feature to transfer DDL only (#23)

Author: techouse

README.md

@@ -42,16 +42,21 @@ Options:
                                   separated table names). Implies --without-
                                   foreign-keys which inhibits the transfer of
                                   foreign keys.
+
   -L, --limit-rows INTEGER        Transfer only a limited number of rows from
                                   each table.
+
   -C, --collation [BINARY|NOCASE|RTRIM]
                                   Create datatypes of TEXT affinity using a
                                   specified collation sequence.  [default:
                                   BINARY]
+
   -K, --prefix-indices            Prefix indices with their corresponding
                                   tables. This ensures that their names remain
                                   unique across the SQLite database.
+
   -X, --without-foreign-keys      Do not transfer foreign keys.
+  -W, --without-data              Do not transfer table data, DDL only.
   -h, --mysql-host TEXT           MySQL host. Defaults to localhost.
   -P, --mysql-port INTEGER        MySQL port. Defaults to 3306.
   -S, --skip-ssl                  Disable MySQL connection encryption.
@@ -61,11 +66,13 @@ Options:
   -V, --vacuum                    Use the VACUUM command to rebuild the SQLite
                                   database file, repacking it into a minimal
                                   amount of disk space
+
   --use-buffered-cursors          Use MySQLCursorBuffered for reading the
                                   MySQL database. This can be useful in
                                   situations where multiple queries, with
                                   small result sets, need to be combined or
                                   computed with each other.
+
   -q, --quiet                     Quiet. Display only errors.
   --version                       Show the version and exit.
   --help                          Show this message and exit.

mysql_to_sqlite3/cli.py

@@ -73,6 +73,12 @@
 @click.option(
     "-X", "--without-foreign-keys", is_flag=True, help="Do not transfer foreign keys."
 )
+@click.option(
+    "-W",
+    "--without-data",
+    is_flag=True,
+    help="Do not transfer table data, DDL only.",
+)
 @click.option(
     "-h", "--mysql-host", default="localhost", help="MySQL host. Defaults to localhost."
 )
@@ -120,6 +126,7 @@ def cli(
     collation,
     prefix_indices,
     without_foreign_keys,
+    without_data,
     mysql_host,
     mysql_port,
     skip_ssl,
@@ -143,6 +150,7 @@ def cli(
             prefix_indices=prefix_indices,
             without_foreign_keys=without_foreign_keys
             or (mysql_tables is not None and len(mysql_tables) > 0),
+            without_data=without_data,
             mysql_host=mysql_host,
             mysql_port=mysql_port,
             mysql_ssl_disabled=skip_ssl,

mysql_to_sqlite3/transporter.py

@@ -70,6 +70,8 @@ def __init__(self, **kwargs):
             else (kwargs.get("without_foreign_keys") or False)
         )
 
+        self._without_data = kwargs.get("without_data") or False
+
         self._mysql_user = str(kwargs.get("mysql_user"))
 
         self._mysql_password = (
@@ -520,58 +522,68 @@ def transfer(self):
             self._sqlite_cur.execute("PRAGMA foreign_keys=OFF")
 
             for table_name in tables:
+                self._logger.info(
+                    "%sTransferring table %s",
+                    "[WITHOUT DATA] " if self._without_data else "",
+                    table_name,
+                )
+
                 # reset the chunk
                 self._current_chunk_number = 0
 
                 # create the table
                 self._create_table(table_name)
 
-                # get the size of the data
-                if self._limit_rows > 0:
-                    # limit to the requested number of rows
-                    self._mysql_cur_dict.execute(
-                        """
-                            SELECT COUNT(*) AS `total_records`
-                            FROM (SELECT * FROM `{table_name}` LIMIT {limit}) AS `table`
-                        """.format(
-                            table_name=table_name, limit=self._limit_rows
+                if not self._without_data:
+                    # get the size of the data
+                    if self._limit_rows > 0:
+                        # limit to the requested number of rows
+                        self._mysql_cur_dict.execute(
+                            """
+                                SELECT COUNT(*) AS `total_records`
+                                FROM (SELECT * FROM `{table_name}` LIMIT {limit}) AS `table`
+                            """.format(
+                                table_name=table_name, limit=self._limit_rows
+                            )
                         )
-                    )
-                else:
-                    # get all rows
-                    self._mysql_cur_dict.execute(
-                        "SELECT COUNT(*) AS `total_records` FROM `{table_name}`".format(
-                            table_name=table_name
+                    else:
+                        # get all rows
+                        self._mysql_cur_dict.execute(
+                            "SELECT COUNT(*) AS `total_records` FROM `{table_name}`".format(
+                                table_name=table_name
+                            )
                         )
+                    total_records = int(
+                        self._mysql_cur_dict.fetchone()["total_records"]
                     )
-                total_records = int(self._mysql_cur_dict.fetchone()["total_records"])
-
-                # only continue if there is anything to transfer
-                if total_records > 0:
-                    # populate it
-                    self._logger.info("Transferring table %s", table_name)
-                    self._mysql_cur.execute(
-                        "SELECT * FROM `{table_name}` {limit}".format(
-                            table_name=table_name,
-                            limit="LIMIT {}".format(self._limit_rows)
-                            if self._limit_rows > 0
-                            else "",
+
+                    # only continue if there is anything to transfer
+                    if total_records > 0:
+                        # populate it
+                        self._mysql_cur.execute(
+                            "SELECT * FROM `{table_name}` {limit}".format(
+                                table_name=table_name,
+                                limit="LIMIT {}".format(self._limit_rows)
+                                if self._limit_rows > 0
+                                else "",
+                            )
+                        )
+                        columns = [column[0] for column in self._mysql_cur.description]
+                        # build the SQL string
+                        sql = """
+                            INSERT OR IGNORE
+                            INTO "{table}" ({fields})
+                            VALUES ({placeholders})
+                        """.format(
+                            table=table_name,
+                            fields=('"{}", ' * len(columns))
+                            .rstrip(" ,")
+                            .format(*columns),
+                            placeholders=("?, " * len(columns)).rstrip(" ,"),
+                        )
+                        self._transfer_table_data(
+                            table_name=table_name, sql=sql, total_records=total_records
                         )
-                    )
-                    columns = [column[0] for column in self._mysql_cur.description]
-                    # build the SQL string
-                    sql = """
-                        INSERT OR IGNORE
-                        INTO "{table}" ({fields})
-                        VALUES ({placeholders})
-                    """.format(
-                        table=table_name,
-                        fields=('"{}", ' * len(columns)).rstrip(" ,").format(*columns),
-                        placeholders=("?, " * len(columns)).rstrip(" ,"),
-                    )
-                    self._transfer_table_data(
-                        table_name=table_name, sql=sql, total_records=total_records
-                    )
         except Exception:  # pylint: disable=W0706
             raise
         finally: