synapse/scripts/synapse_port_db

#!/usr/bin/env python
# Copyright 2015, 2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
# Copyright 2019 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import argparse
import curses
import logging
import sys
import time
import traceback
from typing import Dict, Iterable, Optional, Set

import yaml

from twisted.internet import defer, reactor

import synapse
from synapse.config.database import DatabaseConnectionConfig
from synapse.config.homeserver import HomeServerConfig
from synapse.logging.context import (
    LoggingContext,
    make_deferred_yieldable,
    run_in_background,
)
from synapse.storage.database import DatabasePool, make_conn
from synapse.storage.databases.main.client_ips import ClientIpBackgroundUpdateStore
from synapse.storage.databases.main.deviceinbox import DeviceInboxBackgroundUpdateStore
from synapse.storage.databases.main.devices import DeviceBackgroundUpdateStore
from synapse.storage.databases.main.end_to_end_keys import EndToEndKeyBackgroundStore
from synapse.storage.databases.main.events_bg_updates import (
    EventsBackgroundUpdatesStore,
)
from synapse.storage.databases.main.media_repository import (
    MediaRepositoryBackgroundUpdateStore,
)
from synapse.storage.databases.main.profile import ProfileStore
from synapse.storage.databases.main.pusher import PusherWorkerStore
from synapse.storage.databases.main.registration import (
    RegistrationBackgroundUpdateStore,
    find_max_generated_user_id_localpart,
)
from synapse.storage.databases.main.room import RoomBackgroundUpdateStore
from synapse.storage.databases.main.roommember import RoomMemberBackgroundUpdateStore
from synapse.storage.databases.main.search import SearchBackgroundUpdateStore
from synapse.storage.databases.main.state import MainStateBackgroundUpdateStore
from synapse.storage.databases.main.stats import StatsStore
from synapse.storage.databases.main.user_directory import (
    UserDirectoryBackgroundUpdateStore,
)
from synapse.storage.databases.state.bg_updates import StateBackgroundUpdateStore
from synapse.storage.engines import create_engine
from synapse.storage.prepare_database import prepare_database
from synapse.util import Clock
from synapse.util.versionstring import get_version_string

logger = logging.getLogger("synapse_port_db")


BOOLEAN_COLUMNS = {
    "events": ["processed", "outlier", "contains_url"],
    "rooms": ["is_public", "has_auth_chain_index"],
    "event_edges": ["is_state"],
    "presence_list": ["accepted"],
    "presence_stream": ["currently_active"],
    "public_room_list_stream": ["visibility"],
    "devices": ["hidden"],
    "device_lists_outbound_pokes": ["sent"],
    "users_who_share_rooms": ["share_private"],
    "groups": ["is_public"],
    "group_rooms": ["is_public"],
    "group_users": ["is_public", "is_admin"],
    "group_summary_rooms": ["is_public"],
    "group_room_categories": ["is_public"],
    "group_summary_users": ["is_public"],
    "group_roles": ["is_public"],
    "local_group_membership": ["is_publicised", "is_admin"],
    "e2e_room_keys": ["is_verified"],
    "account_validity": ["email_sent"],
    "redactions": ["have_censored"],
    "room_stats_state": ["is_federatable"],
    "local_media_repository": ["safe_from_quarantine"],
    "users": ["shadow_banned"],
    "e2e_fallback_keys_json": ["used"],
}


APPEND_ONLY_TABLES = [
    "event_reference_hashes",
    "events",
    "event_json",
    "state_events",
    "room_memberships",
    "topics",
    "room_names",
    "rooms",
    "local_media_repository",
    "local_media_repository_thumbnails",
    "remote_media_cache",
    "remote_media_cache_thumbnails",
    "redactions",
    "event_edges",
    "event_auth",
    "received_transactions",
    "sent_transactions",
    "transaction_id_to_pdu",
    "users",
    "state_groups",
    "state_groups_state",
    "event_to_state_groups",
    "rejections",
    "event_search",
    "presence_stream",
    "push_rules_stream",
    "ex_outlier_stream",
    "cache_invalidation_stream_by_instance",
    "public_room_list_stream",
    "state_group_edges",
    "stream_ordering_to_exterm",
]


IGNORED_TABLES = {
    # We don't port these tables, as they're a faff and we can regenerate
    # them anyway.
    "user_directory",
    "user_directory_search",
    "user_directory_search_content",
    "user_directory_search_docsize",
    "user_directory_search_segdir",
    "user_directory_search_segments",
    "user_directory_search_stat",
    "user_directory_search_pos",
    "users_who_share_private_rooms",
    "users_in_public_room",
    # UI auth sessions have foreign keys so additional care needs to be taken,
    # the sessions are transient anyway, so ignore them.
    "ui_auth_sessions",
    "ui_auth_sessions_credentials",
    "ui_auth_sessions_ips",
}


# Error returned by the run function. Used at the top-level part of the script to
# handle errors and return codes.
end_error = None  # type: Optional[str]
# The exec_info for the error, if any. If error is defined but not exec_info the script
# will show only the error message without the stacktrace, if exec_info is defined but
# not the error then the script will show nothing outside of what's printed in the run
# function. If both are defined, the script will print both the error and the stacktrace.
end_error_exec_info = None


class Store(
    ClientIpBackgroundUpdateStore,
    DeviceInboxBackgroundUpdateStore,
    DeviceBackgroundUpdateStore,
    EventsBackgroundUpdatesStore,
    MediaRepositoryBackgroundUpdateStore,
    ProfileStore,
    RegistrationBackgroundUpdateStore,
    RoomBackgroundUpdateStore,
    RoomMemberBackgroundUpdateStore,
    SearchBackgroundUpdateStore,
    StateBackgroundUpdateStore,
    MainStateBackgroundUpdateStore,
    UserDirectoryBackgroundUpdateStore,
    EndToEndKeyBackgroundStore,
    StatsStore,
    PusherWorkerStore,
):
    def execute(self, f, *args, **kwargs):
        return self.db_pool.runInteraction(f.__name__, f, *args, **kwargs)

    def execute_sql(self, sql, *args):
        def r(txn):
            txn.execute(sql, args)
            return txn.fetchall()

        return self.db_pool.runInteraction("execute_sql", r)

    def insert_many_txn(self, txn, table, headers, rows):
        sql = "INSERT INTO %s (%s) VALUES (%s)" % (
            table,
            ", ".join(k for k in headers),
            ", ".join("%s" for _ in headers),
        )

        try:
            txn.executemany(sql, rows)
        except Exception:
            logger.exception("Failed to insert: %s", table)
            raise

    def set_room_is_public(self, room_id, is_public):
        raise Exception(
            "Attempt to set room_is_public during port_db: database not empty?"
        )


class MockHomeserver:
    def __init__(self, config):
        self.clock = Clock(reactor)
        self.config = config
        self.hostname = config.server_name
        self.version_string = "Synapse/" + get_version_string(synapse)

    def get_clock(self):
        return self.clock

    def get_reactor(self):
        return reactor

    def get_instance_name(self):
        return "master"


class Porter(object):
    def __init__(self, **kwargs):
        self.__dict__.update(kwargs)

    async def setup_table(self, table):
        if table in APPEND_ONLY_TABLES:
            # It's safe to just carry on inserting.
            row = await self.postgres_store.db_pool.simple_select_one(
                table="port_from_sqlite3",
                keyvalues={"table_name": table},
                retcols=("forward_rowid", "backward_rowid"),
                allow_none=True,
            )

            total_to_port = None
            if row is None:
                if table == "sent_transactions":
                    (
                        forward_chunk,
                        already_ported,
                        total_to_port,
                    ) = await self._setup_sent_transactions()
                    backward_chunk = 0
                else:
                    await self.postgres_store.db_pool.simple_insert(
                        table="port_from_sqlite3",
                        values={
                            "table_name": table,
                            "forward_rowid": 1,
                            "backward_rowid": 0,
                        },
                    )

                    forward_chunk = 1
                    backward_chunk = 0
                    already_ported = 0
            else:
                forward_chunk = row["forward_rowid"]
                backward_chunk = row["backward_rowid"]

            if total_to_port is None:
                already_ported, total_to_port = await self._get_total_count_to_port(
                    table, forward_chunk, backward_chunk
                )
        else:

            def delete_all(txn):
                txn.execute(
                    "DELETE FROM port_from_sqlite3 WHERE table_name = %s", (table,)
                )
                txn.execute("TRUNCATE %s CASCADE" % (table,))

            await self.postgres_store.execute(delete_all)

            await self.postgres_store.db_pool.simple_insert(
                table="port_from_sqlite3",
                values={"table_name": table, "forward_rowid": 1, "backward_rowid": 0},
            )

            forward_chunk = 1
            backward_chunk = 0

            already_ported, total_to_port = await self._get_total_count_to_port(
                table, forward_chunk, backward_chunk
            )

        return table, already_ported, total_to_port, forward_chunk, backward_chunk

    async def get_table_constraints(self) -> Dict[str, Set[str]]:
        """Returns a map of tables that have foreign key constraints to tables they depend on."""

        def _get_constraints(txn):
            # We can pull the information about foreign key constraints out from
            # the postgres schema tables.
            sql = """
                SELECT DISTINCT
                    tc.table_name,
                    ccu.table_name AS foreign_table_name
                FROM
                    information_schema.table_constraints AS tc
                    INNER JOIN information_schema.constraint_column_usage AS ccu
                    USING (table_schema, constraint_name)
                WHERE tc.constraint_type = 'FOREIGN KEY';
            """
            txn.execute(sql)

            results = {}
            for table, foreign_table in txn:
                results.setdefault(table, set()).add(foreign_table)
            return results

        return await self.postgres_store.db_pool.runInteraction(
            "get_table_constraints", _get_constraints
        )

    async def handle_table(
        self, table, postgres_size, table_size, forward_chunk, backward_chunk
    ):
        logger.info(
            "Table %s: %i/%i (rows %i-%i) already ported",
            table,
            postgres_size,
            table_size,
            backward_chunk + 1,
            forward_chunk - 1,
        )

        if not table_size:
            return

        self.progress.add_table(table, postgres_size, table_size)

        if table == "event_search":
            await self.handle_search_table(
                postgres_size, table_size, forward_chunk, backward_chunk
            )
            return

        if table in IGNORED_TABLES:
            self.progress.update(table, table_size)  # Mark table as done
            return

        if table == "user_directory_stream_pos":
            # We need to make sure there is a single row, `(X, null), as that is
            # what synapse expects to be there.
            await self.postgres_store.db_pool.simple_insert(
                table=table, values={"stream_id": None}
            )
            self.progress.update(table, table_size)  # Mark table as done
            return

        forward_select = (
            "SELECT rowid, * FROM %s WHERE rowid >= ? ORDER BY rowid LIMIT ?" % (table,)
        )

        backward_select = (
            "SELECT rowid, * FROM %s WHERE rowid <= ? ORDER BY rowid LIMIT ?" % (table,)
        )

        do_forward = [True]
        do_backward = [True]

        while True:

            def r(txn):
                forward_rows = []
                backward_rows = []
                if do_forward[0]:
                    txn.execute(forward_select, (forward_chunk, self.batch_size))
                    forward_rows = txn.fetchall()
                    if not forward_rows:
                        do_forward[0] = False

                if do_backward[0]:
                    txn.execute(backward_select, (backward_chunk, self.batch_size))
                    backward_rows = txn.fetchall()
                    if not backward_rows:
                        do_backward[0] = False

                if forward_rows or backward_rows:
                    headers = [column[0] for column in txn.description]
                else:
                    headers = None

                return headers, forward_rows, backward_rows

            headers, frows, brows = await self.sqlite_store.db_pool.runInteraction(
                "select", r
            )

            if frows or brows:
                if frows:
                    forward_chunk = max(row[0] for row in frows) + 1
                if brows:
                    backward_chunk = min(row[0] for row in brows) - 1

                rows = frows + brows
                rows = self._convert_rows(table, headers, rows)

                def insert(txn):
                    self.postgres_store.insert_many_txn(txn, table, headers[1:], rows)

                    self.postgres_store.db_pool.simple_update_one_txn(
                        txn,
                        table="port_from_sqlite3",
                        keyvalues={"table_name": table},
                        updatevalues={
                            "forward_rowid": forward_chunk,
                            "backward_rowid": backward_chunk,
                        },
                    )

                await self.postgres_store.execute(insert)

                postgres_size += len(rows)

                self.progress.update(table, postgres_size)
            else:
                return

    async def handle_search_table(
        self, postgres_size, table_size, forward_chunk, backward_chunk
    ):
        select = (
            "SELECT es.rowid, es.*, e.origin_server_ts, e.stream_ordering"
            " FROM event_search as es"
            " INNER JOIN events AS e USING (event_id, room_id)"
            " WHERE es.rowid >= ?"
            " ORDER BY es.rowid LIMIT ?"
        )

        while True:

            def r(txn):
                txn.execute(select, (forward_chunk, self.batch_size))
                rows = txn.fetchall()
                headers = [column[0] for column in txn.description]

                return headers, rows

            headers, rows = await self.sqlite_store.db_pool.runInteraction("select", r)

            if rows:
                forward_chunk = rows[-1][0] + 1

                # We have to treat event_search differently since it has a
                # different structure in the two different databases.
                def insert(txn):
                    sql = (
                        "INSERT INTO event_search (event_id, room_id, key,"
                        " sender, vector, origin_server_ts, stream_ordering)"
                        " VALUES (?,?,?,?,to_tsvector('english', ?),?,?)"
                    )

                    rows_dict = []
                    for row in rows:
                        d = dict(zip(headers, row))
                        if "\0" in d["value"]:
                            logger.warning("dropping search row %s", d)
                        else:
                            rows_dict.append(d)

                    txn.executemany(
                        sql,
                        [
                            (
                                row["event_id"],
                                row["room_id"],
                                row["key"],
                                row["sender"],
                                row["value"],
                                row["origin_server_ts"],
                                row["stream_ordering"],
                            )
                            for row in rows_dict
                        ],
                    )

                    self.postgres_store.db_pool.simple_update_one_txn(
                        txn,
                        table="port_from_sqlite3",
                        keyvalues={"table_name": "event_search"},
                        updatevalues={
                            "forward_rowid": forward_chunk,
                            "backward_rowid": backward_chunk,
                        },
                    )

                await self.postgres_store.execute(insert)

                postgres_size += len(rows)

                self.progress.update("event_search", postgres_size)

            else:
                return

    def build_db_store(
        self,
        db_config: DatabaseConnectionConfig,
        allow_outdated_version: bool = False,
    ):
        """Builds and returns a database store using the provided configuration.

        Args:
            db_config: The database configuration
            allow_outdated_version: True to suppress errors about the database server
                version being too old to run a complete synapse

        Returns:
            The built Store object.
        """
        self.progress.set_state("Preparing %s" % db_config.config["name"])

        engine = create_engine(db_config.config)

        hs = MockHomeserver(self.hs_config)

        with make_conn(db_config, engine, "portdb") as db_conn:
            engine.check_database(
                db_conn, allow_outdated_version=allow_outdated_version
            )
            prepare_database(db_conn, engine, config=self.hs_config)
            store = Store(DatabasePool(hs, db_config, engine), db_conn, hs)
            db_conn.commit()

        return store

    async def run_background_updates_on_postgres(self):
        # Manually apply all background updates on the PostgreSQL database.
        postgres_ready = (
            await self.postgres_store.db_pool.updates.has_completed_background_updates()
        )

        if not postgres_ready:
            # Only say that we're running background updates when there are background
            # updates to run.
            self.progress.set_state("Running background updates on PostgreSQL")

        while not postgres_ready:
            await self.postgres_store.db_pool.updates.do_next_background_update(100)
            postgres_ready = await (
                self.postgres_store.db_pool.updates.has_completed_background_updates()
            )

    async def run(self):
        """Ports the SQLite database to a PostgreSQL database.

        When a fatal error is met, its message is assigned to the global "end_error"
        variable. When this error comes with a stacktrace, its exec_info is assigned to
        the global "end_error_exec_info" variable.
        """
        global end_error

        try:
            # we allow people to port away from outdated versions of sqlite.
            self.sqlite_store = self.build_db_store(
                DatabaseConnectionConfig("master-sqlite", self.sqlite_config),
                allow_outdated_version=True,
            )

            # Check if all background updates are done, abort if not.
            updates_complete = (
                await self.sqlite_store.db_pool.updates.has_completed_background_updates()
            )
            if not updates_complete:
                end_error = (
                    "Pending background updates exist in the SQLite3 database."
                    " Please start Synapse again and wait until every update has finished"
                    " before running this script.\n"
                )
                return

            self.postgres_store = self.build_db_store(
                self.hs_config.get_single_database()
            )

            await self.run_background_updates_on_postgres()

            self.progress.set_state("Creating port tables")

            def create_port_table(txn):
                txn.execute(
                    "CREATE TABLE IF NOT EXISTS port_from_sqlite3 ("
                    " table_name varchar(100) NOT NULL UNIQUE,"
                    " forward_rowid bigint NOT NULL,"
                    " backward_rowid bigint NOT NULL"
                    ")"
                )

            # The old port script created a table with just a "rowid" column.
            # We want people to be able to rerun this script from an old port
            # so that they can pick up any missing events that were not
            # ported across.
            def alter_table(txn):
                txn.execute(
                    "ALTER TABLE IF EXISTS port_from_sqlite3"
                    " RENAME rowid TO forward_rowid"
                )
                txn.execute(
                    "ALTER TABLE IF EXISTS port_from_sqlite3"
                    " ADD backward_rowid bigint NOT NULL DEFAULT 0"
                )

            try:
                await self.postgres_store.db_pool.runInteraction(
                    "alter_table", alter_table
                )
            except Exception:
                # On Error Resume Next
                pass

            await self.postgres_store.db_pool.runInteraction(
                "create_port_table", create_port_table
            )

            # Step 2. Set up sequences
            #
            # We do this before porting the tables so that event if we fail half
            # way through the postgres DB always have sequences that are greater
            # than their respective tables. If we don't then creating the
            # `DataStore` object will fail due to the inconsistency.
            self.progress.set_state("Setting up sequence generators")
            await self._setup_state_group_id_seq()
            await self._setup_user_id_seq()
            await self._setup_events_stream_seqs()
            await self._setup_sequence(
                "device_inbox_sequence", ("device_inbox", "device_federation_outbox")
            )
            await self._setup_sequence(
                "account_data_sequence",
                ("room_account_data", "room_tags_revisions", "account_data"),
            )
            await self._setup_sequence("receipts_sequence", ("receipts_linearized",))
            await self._setup_sequence("presence_stream_sequence", ("presence_stream",))
            await self._setup_auth_chain_sequence()

            # Step 3. Get tables.
            self.progress.set_state("Fetching tables")
            sqlite_tables = await self.sqlite_store.db_pool.simple_select_onecol(
                table="sqlite_master", keyvalues={"type": "table"}, retcol="name"
            )

            postgres_tables = await self.postgres_store.db_pool.simple_select_onecol(
                table="information_schema.tables",
                keyvalues={},
                retcol="distinct table_name",
            )

            tables = set(sqlite_tables) & set(postgres_tables)
            logger.info("Found %d tables", len(tables))

            # Step 4. Figure out what still needs copying
            self.progress.set_state("Checking on port progress")
            setup_res = await make_deferred_yieldable(
                defer.gatherResults(
                    [
                        run_in_background(self.setup_table, table)
                        for table in tables
                        if table not in ["schema_version", "applied_schema_deltas"]
                        and not table.startswith("sqlite_")
                    ],
                    consumeErrors=True,
                )
            )
            # Map from table name to args passed to `handle_table`, i.e. a tuple
            # of: `postgres_size`, `table_size`, `forward_chunk`, `backward_chunk`.
            tables_to_port_info_map = {r[0]: r[1:] for r in setup_res}

            # Step 5. Do the copying.
            #
            # This is slightly convoluted as we need to ensure tables are ported
            # in the correct order due to foreign key constraints.
            self.progress.set_state("Copying to postgres")

            constraints = await self.get_table_constraints()
            tables_ported = set()  # type: Set[str]

            while tables_to_port_info_map:
                # Pulls out all tables that are still to be ported and which
                # only depend on tables that are already ported (if any).
                tables_to_port = [
                    table
                    for table in tables_to_port_info_map
                    if not constraints.get(table, set()) - tables_ported
                ]

                await make_deferred_yieldable(
                    defer.gatherResults(
                        [
                            run_in_background(
                                self.handle_table,
                                table,
                                *tables_to_port_info_map.pop(table),
                            )
                            for table in tables_to_port
                        ],
                        consumeErrors=True,
                    )
                )

                tables_ported.update(tables_to_port)

            self.progress.done()
        except Exception as e:
            global end_error_exec_info
            end_error = str(e)
            end_error_exec_info = sys.exc_info()
            logger.exception("")
        finally:
            reactor.stop()

    def _convert_rows(self, table, headers, rows):
        bool_col_names = BOOLEAN_COLUMNS.get(table, [])

        bool_cols = [i for i, h in enumerate(headers) if h in bool_col_names]

        class BadValueException(Exception):
            pass

        def conv(j, col):
            if j in bool_cols:
                return bool(col)
            if isinstance(col, bytes):
                return bytearray(col)
            elif isinstance(col, str) and "\0" in col:
                logger.warning(
                    "DROPPING ROW: NUL value in table %s col %s: %r",
                    table,
                    headers[j],
                    col,
                )
                raise BadValueException()
            return col

        outrows = []
        for row in rows:
            try:
                outrows.append(
                    tuple(conv(j, col) for j, col in enumerate(row) if j > 0)
                )
            except BadValueException:
                pass

        return outrows

    async def _setup_sent_transactions(self):
        # Only save things from the last day
        yesterday = int(time.time() * 1000) - 86400000

        # And save the max transaction id from each destination
        select = (
            "SELECT rowid, * FROM sent_transactions WHERE rowid IN ("
            "SELECT max(rowid) FROM sent_transactions"
            " GROUP BY destination"
            ")"
        )

        def r(txn):
            txn.execute(select)
            rows = txn.fetchall()
            headers = [column[0] for column in txn.description]

            ts_ind = headers.index("ts")

            return headers, [r for r in rows if r[ts_ind] < yesterday]

        headers, rows = await self.sqlite_store.db_pool.runInteraction("select", r)

        rows = self._convert_rows("sent_transactions", headers, rows)

        inserted_rows = len(rows)
        if inserted_rows:
            max_inserted_rowid = max(r[0] for r in rows)

            def insert(txn):
                self.postgres_store.insert_many_txn(
                    txn, "sent_transactions", headers[1:], rows
                )

            await self.postgres_store.execute(insert)
        else:
            max_inserted_rowid = 0

        def get_start_id(txn):
            txn.execute(
                "SELECT rowid FROM sent_transactions WHERE ts >= ?"
                " ORDER BY rowid ASC LIMIT 1",
                (yesterday,),
            )

            rows = txn.fetchall()
            if rows:
                return rows[0][0]
            else:
                return 1

        next_chunk = await self.sqlite_store.execute(get_start_id)
        next_chunk = max(max_inserted_rowid + 1, next_chunk)

        await self.postgres_store.db_pool.simple_insert(
            table="port_from_sqlite3",
            values={
                "table_name": "sent_transactions",
                "forward_rowid": next_chunk,
                "backward_rowid": 0,
            },
        )

        def get_sent_table_size(txn):
            txn.execute(
                "SELECT count(*) FROM sent_transactions" " WHERE ts >= ?", (yesterday,)
            )
            (size,) = txn.fetchone()
            return int(size)

        remaining_count = await self.sqlite_store.execute(get_sent_table_size)

        total_count = remaining_count + inserted_rows

        return next_chunk, inserted_rows, total_count

    async def _get_remaining_count_to_port(self, table, forward_chunk, backward_chunk):
        frows = await self.sqlite_store.execute_sql(
            "SELECT count(*) FROM %s WHERE rowid >= ?" % (table,), forward_chunk
        )

        brows = await self.sqlite_store.execute_sql(
            "SELECT count(*) FROM %s WHERE rowid <= ?" % (table,), backward_chunk
        )

        return frows[0][0] + brows[0][0]

    async def _get_already_ported_count(self, table):
        rows = await self.postgres_store.execute_sql(
            "SELECT count(*) FROM %s" % (table,)
        )

        return rows[0][0]

    async def _get_total_count_to_port(self, table, forward_chunk, backward_chunk):
        remaining, done = await make_deferred_yieldable(
            defer.gatherResults(
                [
                    run_in_background(
                        self._get_remaining_count_to_port,
                        table,
                        forward_chunk,
                        backward_chunk,
                    ),
                    run_in_background(self._get_already_ported_count, table),
                ],
            )
        )

        remaining = int(remaining) if remaining else 0
        done = int(done) if done else 0

        return done, remaining + done

    async def _setup_state_group_id_seq(self) -> None:
        curr_id = await self.sqlite_store.db_pool.simple_select_one_onecol(
            table="state_groups", keyvalues={}, retcol="MAX(id)", allow_none=True
        )

        if not curr_id:
            return

        def r(txn):
            next_id = curr_id + 1
            txn.execute("ALTER SEQUENCE state_group_id_seq RESTART WITH %s", (next_id,))

        await self.postgres_store.db_pool.runInteraction("setup_state_group_id_seq", r)

    async def _setup_user_id_seq(self) -> None:
        curr_id = await self.sqlite_store.db_pool.runInteraction(
            "setup_user_id_seq", find_max_generated_user_id_localpart
        )

        def r(txn):
            next_id = curr_id + 1
            txn.execute("ALTER SEQUENCE user_id_seq RESTART WITH %s", (next_id,))

        await self.postgres_store.db_pool.runInteraction("setup_user_id_seq", r)

    async def _setup_events_stream_seqs(self) -> None:
        """Set the event stream sequences to the correct values."""

        # We get called before we've ported the events table, so we need to
        # fetch the current positions from the SQLite store.
        curr_forward_id = await self.sqlite_store.db_pool.simple_select_one_onecol(
            table="events", keyvalues={}, retcol="MAX(stream_ordering)", allow_none=True
        )

        curr_backward_id = await self.sqlite_store.db_pool.simple_select_one_onecol(
            table="events",
            keyvalues={},
            retcol="MAX(-MIN(stream_ordering), 1)",
            allow_none=True,
        )

        def _setup_events_stream_seqs_set_pos(txn):
            if curr_forward_id:
                txn.execute(
                    "ALTER SEQUENCE events_stream_seq RESTART WITH %s",
                    (curr_forward_id + 1,),
                )

            if curr_backward_id:
                txn.execute(
                    "ALTER SEQUENCE events_backfill_stream_seq RESTART WITH %s",
                    (curr_backward_id + 1,),
                )

        await self.postgres_store.db_pool.runInteraction(
            "_setup_events_stream_seqs",
            _setup_events_stream_seqs_set_pos,
        )

    async def _setup_sequence(
        self, sequence_name: str, stream_id_tables: Iterable[str]
    ) -> None:
        """Set a sequence to the correct value."""
        current_stream_ids = []
        for stream_id_table in stream_id_tables:
            max_stream_id = await self.sqlite_store.db_pool.simple_select_one_onecol(
                table=stream_id_table,
                keyvalues={},
                retcol="COALESCE(MAX(stream_id), 1)",
                allow_none=True,
            )
            current_stream_ids.append(max_stream_id)

        next_id = max(current_stream_ids) + 1

        def r(txn):
            sql = "ALTER SEQUENCE %s RESTART WITH" % (sequence_name,)
            txn.execute(sql + " %s", (next_id,))

        await self.postgres_store.db_pool.runInteraction(
            "_setup_%s" % (sequence_name,), r
        )

    async def _setup_auth_chain_sequence(self) -> None:
        curr_chain_id = await self.sqlite_store.db_pool.simple_select_one_onecol(
            table="event_auth_chains",
            keyvalues={},
            retcol="MAX(chain_id)",
            allow_none=True,
        )

        def r(txn):
            txn.execute(
                "ALTER SEQUENCE event_auth_chain_id RESTART WITH %s",
                (curr_chain_id + 1,),
            )

        if curr_chain_id is not None:
            await self.postgres_store.db_pool.runInteraction(
                "_setup_event_auth_chain_id",
                r,
            )


##############################################
# The following is simply UI stuff
##############################################


class Progress(object):
    """Used to report progress of the port"""

    def __init__(self):
        self.tables = {}

        self.start_time = int(time.time())

    def add_table(self, table, cur, size):
        self.tables[table] = {
            "start": cur,
            "num_done": cur,
            "total": size,
            "perc": int(cur * 100 / size),
        }

    def update(self, table, num_done):
        data = self.tables[table]
        data["num_done"] = num_done
        data["perc"] = int(num_done * 100 / data["total"])

    def done(self):
        pass


class CursesProgress(Progress):
    """Reports progress to a curses window"""

    def __init__(self, stdscr):
        self.stdscr = stdscr

        curses.use_default_colors()
        curses.curs_set(0)

        curses.init_pair(1, curses.COLOR_RED, -1)
        curses.init_pair(2, curses.COLOR_GREEN, -1)

        self.last_update = 0

        self.finished = False

        self.total_processed = 0
        self.total_remaining = 0

        super(CursesProgress, self).__init__()

    def update(self, table, num_done):
        super(CursesProgress, self).update(table, num_done)

        self.total_processed = 0
        self.total_remaining = 0
        for data in self.tables.values():
            self.total_processed += data["num_done"] - data["start"]
            self.total_remaining += data["total"] - data["num_done"]

        self.render()

    def render(self, force=False):
        now = time.time()

        if not force and now - self.last_update < 0.2:
            # reactor.callLater(1, self.render)
            return

        self.stdscr.clear()

        rows, cols = self.stdscr.getmaxyx()

        duration = int(now) - int(self.start_time)

        minutes, seconds = divmod(duration, 60)
        duration_str = "%02dm %02ds" % (minutes, seconds)

        if self.finished:
            status = "Time spent: %s (Done!)" % (duration_str,)
        else:

            if self.total_processed > 0:
                left = float(self.total_remaining) / self.total_processed

                est_remaining = (int(now) - self.start_time) * left
                est_remaining_str = "%02dm %02ds remaining" % divmod(est_remaining, 60)
            else:
                est_remaining_str = "Unknown"
            status = "Time spent: %s (est. remaining: %s)" % (
                duration_str,
                est_remaining_str,
            )

        self.stdscr.addstr(0, 0, status, curses.A_BOLD)

        max_len = max([len(t) for t in self.tables.keys()])

        left_margin = 5
        middle_space = 1

        items = self.tables.items()
        items = sorted(items, key=lambda i: (i[1]["perc"], i[0]))

        for i, (table, data) in enumerate(items):
            if i + 2 >= rows:
                break

            perc = data["perc"]

            color = curses.color_pair(2) if perc == 100 else curses.color_pair(1)

            self.stdscr.addstr(
                i + 2, left_margin + max_len - len(table), table, curses.A_BOLD | color
            )

            size = 20

            progress = "[%s%s]" % (
                "#" * int(perc * size / 100),
                " " * (size - int(perc * size / 100)),
            )

            self.stdscr.addstr(
                i + 2,
                left_margin + max_len + middle_space,
                "%s %3d%% (%d/%d)" % (progress, perc, data["num_done"], data["total"]),
            )

        if self.finished:
            self.stdscr.addstr(rows - 1, 0, "Press any key to exit...")

        self.stdscr.refresh()
        self.last_update = time.time()

    def done(self):
        self.finished = True
        self.render(True)
        self.stdscr.getch()

    def set_state(self, state):
        self.stdscr.clear()
        self.stdscr.addstr(0, 0, state + "...", curses.A_BOLD)
        self.stdscr.refresh()


class TerminalProgress(Progress):
    """Just prints progress to the terminal"""

    def update(self, table, num_done):
        super(TerminalProgress, self).update(table, num_done)

        data = self.tables[table]

        print(
            "%s: %d%% (%d/%d)" % (table, data["perc"], data["num_done"], data["total"])
        )

    def set_state(self, state):
        print(state + "...")


##############################################
##############################################


if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description="A script to port an existing synapse SQLite database to"
        " a new PostgreSQL database."
    )
    parser.add_argument("-v", action="store_true")
    parser.add_argument(
        "--sqlite-database",
        required=True,
        help="The snapshot of the SQLite database file. This must not be"
        " currently used by a running synapse server",
    )
    parser.add_argument(
        "--postgres-config",
        type=argparse.FileType("r"),
        required=True,
        help="The database config file for the PostgreSQL database",
    )
    parser.add_argument(
        "--curses", action="store_true", help="display a curses based progress UI"
    )

    parser.add_argument(
        "--batch-size",
        type=int,
        default=1000,
        help="The number of rows to select from the SQLite table each"
        " iteration [default=1000]",
    )

    args = parser.parse_args()

    logging_config = {
        "level": logging.DEBUG if args.v else logging.INFO,
        "format": "%(asctime)s - %(name)s - %(lineno)d - %(levelname)s - %(message)s",
    }

    if args.curses:
        logging_config["filename"] = "port-synapse.log"

    logging.basicConfig(**logging_config)

    sqlite_config = {
        "name": "sqlite3",
        "args": {
            "database": args.sqlite_database,
            "cp_min": 1,
            "cp_max": 1,
            "check_same_thread": False,
        },
    }

    hs_config = yaml.safe_load(args.postgres_config)

    if "database" not in hs_config:
        sys.stderr.write("The configuration file must have a 'database' section.\n")
        sys.exit(4)

    postgres_config = hs_config["database"]

    if "name" not in postgres_config:
        sys.stderr.write("Malformed database config: no 'name'\n")
        sys.exit(2)
    if postgres_config["name"] != "psycopg2":
        sys.stderr.write("Database must use the 'psycopg2' connector.\n")
        sys.exit(3)

    config = HomeServerConfig()
    config.parse_config_dict(hs_config, "", "")

    def start(stdscr=None):
        if stdscr:
            progress = CursesProgress(stdscr)
        else:
            progress = TerminalProgress()

        porter = Porter(
            sqlite_config=sqlite_config,
            progress=progress,
            batch_size=args.batch_size,
            hs_config=config,
        )

        @defer.inlineCallbacks
        def run():
            with LoggingContext("synapse_port_db_run"):
                yield defer.ensureDeferred(porter.run())

        reactor.callWhenRunning(run)

        reactor.run()

    if args.curses:
        curses.wrapper(start)
    else:
        start()

    if end_error:
        if end_error_exec_info:
            exc_type, exc_value, exc_traceback = end_error_exec_info
            traceback.print_exception(exc_type, exc_value, exc_traceback)

        sys.stderr.write(end_error)

        sys.exit(5)