nilmdb/nilmdb/server/nilmdb.py

# -*- coding: utf-8 -*-

"""NilmDB

Object that represents a NILM database file.

Manages both the SQL database and the table storage backend.
"""

# Need absolute_import so that "import nilmdb" won't pull in
# nilmdb.py, but will pull the parent nilmdb module instead.
from __future__ import absolute_import
import nilmdb
from nilmdb.utils.printf import *
from nilmdb.server.interval import (Interval, DBInterval,
                                    IntervalSet, IntervalError)
from nilmdb.server import bulkdata
from nilmdb.server.errors import NilmDBError, StreamError, OverlapError

import sqlite3
import os
import errno
import bisect

# Note about performance and transactions:
#
# Committing a transaction in the default sync mode (PRAGMA synchronous=FULL)
# takes about 125msec.  sqlite3 will commit transactions at 3 times:
# 1: explicit con.commit()
# 2: between a series of DML commands and non-DML commands, e.g.
#    after a series of INSERT, SELECT, but before a CREATE TABLE or PRAGMA.
# 3: at the end of an explicit transaction, e.g. "with self.con as con:"
#
# To speed up testing, or if this transaction speed becomes an issue,
# the sync=False option to NilmDB.__init__ will set PRAGMA synchronous=OFF.


# Don't touch old entries -- just add new ones.
_sql_schema_updates = {
    0: """
    -- All streams
    CREATE TABLE streams(
    	id INTEGER PRIMARY KEY,		-- stream ID
        path TEXT UNIQUE NOT NULL,	-- path, e.g. '/newton/prep'
        layout TEXT NOT NULL		-- layout name, e.g. float32_8
    );

    -- Individual timestamped ranges in those streams.
    -- For a given start_time and end_time, this tells us that the
    -- data is stored between start_pos and end_pos.
    -- Times are stored as μs since Unix epoch
    -- Positions are opaque: PyTables rows, file offsets, etc.
    --
    -- Note: end_pos points to the row _after_ end_time, so end_pos-1
    -- is the last valid row.
    CREATE TABLE ranges(
        stream_id INTEGER NOT NULL,
        start_time INTEGER NOT NULL,
        end_time INTEGER NOT NULL,
        start_pos INTEGER NOT NULL,
        end_pos INTEGER NOT NULL
    );
    CREATE INDEX _ranges_index ON ranges (stream_id, start_time, end_time);
    """,

    1: """
    -- Generic dictionary-type metadata that can be associated with a stream
    CREATE TABLE metadata(
    	stream_id INTEGER NOT NULL,
        key TEXT NOT NULL,
        value TEXT
    );
    """,
}

@nilmdb.utils.must_close()
class NilmDB(object):
    verbose = 0

    def __init__(self, basepath, sync=True, max_results=None,
                 bulkdata_args=None):
        if bulkdata_args is None:
            bulkdata_args = {}

        # set up path
        self.basepath = os.path.abspath(basepath)

        # Create the database path if it doesn't exist
        try:
            os.makedirs(self.basepath)
        except OSError as e:
            if e.errno != errno.EEXIST:
                raise IOError("can't create tree " + self.basepath)

        # Our data goes inside it
        self.data = bulkdata.BulkData(self.basepath, **bulkdata_args)

        # SQLite database too
        sqlfilename = os.path.join(self.basepath, "data.sql")
        # We use check_same_thread = False, assuming that the rest
        # of the code (e.g. Server) will be smart and not access this
        # database from multiple threads simultaneously.  Otherwise
        # false positives will occur when the database is only opened
        # in one thread, and only accessed in another.
        self.con = sqlite3.connect(sqlfilename, check_same_thread = False)
        self._sql_schema_update()

        # See big comment at top about the performance implications of this
        if sync:
            self.con.execute("PRAGMA synchronous=FULL")
        else:
            self.con.execute("PRAGMA synchronous=OFF")

        # Approximate largest number of elements that we want to send
        # in a single reply (for stream_intervals, stream_extract)
        if max_results:
            self.max_results = max_results
        else:
            self.max_results = 16384

    def get_basepath(self):
        return self.basepath

    def close(self):
        if self.con:
            self.con.commit()
            self.con.close()
        self.data.close()

    def _sql_schema_update(self):
        cur = self.con.cursor()
        version = cur.execute("PRAGMA user_version").fetchone()[0]
        oldversion = version

        while version in _sql_schema_updates:
            cur.executescript(_sql_schema_updates[version])
            version = version + 1
            if self.verbose: # pragma: no cover
                printf("Schema updated to %d\n", version)

        if version != oldversion:
            with self.con:
                cur.execute("PRAGMA user_version = {v:d}".format(v=version))

    def _fill_in_limits(self, start, end):
        if start is None:
            start = -1e12
        if end is None:
            end = 1e12
        return (start, end)

    @nilmdb.utils.lru_cache(size = 16)
    def _get_intervals(self, stream_id):
        """
        Return a mutable IntervalSet corresponding to the given stream ID.
        """
        iset = IntervalSet()
        result = self.con.execute("SELECT start_time, end_time, "
                                  "start_pos, end_pos "
                                  "FROM ranges "
                                  "WHERE stream_id=?", (stream_id,))
        try:
            for (start_time, end_time, start_pos, end_pos) in result:
                iset += DBInterval(start_time, end_time,
                                   start_time, end_time,
                                   start_pos, end_pos)
        except IntervalError: # pragma: no cover
            raise NilmDBError("unexpected overlap in ranges table!")

        return iset

    def _sql_interval_insert(self, id, start, end, start_pos, end_pos):
        """Helper that adds interval to the SQL database only"""
        self.con.execute("INSERT INTO ranges "
                         "(stream_id,start_time,end_time,start_pos,end_pos) "
                         "VALUES (?,?,?,?,?)",
                         (id, start, end, start_pos, end_pos))

    def _sql_interval_delete(self, id, start, end, start_pos, end_pos):
        """Helper that removes interval from the SQL database only"""
        self.con.execute("DELETE FROM ranges WHERE "
                         "stream_id=? AND start_time=? AND "
                         "end_time=? AND start_pos=? AND end_pos=?",
                         (id, start, end, start_pos, end_pos))

    def _add_interval(self, stream_id, interval, start_pos, end_pos):
        """
        Add interval to the internal interval cache, and to the database.
        Note: arguments must be ints (not numpy.int64, etc)
        """
        # Load this stream's intervals
        iset = self._get_intervals(stream_id)

        # Check for overlap
        if iset.intersects(interval): # pragma: no cover (gets caught earlier)
            raise NilmDBError("new interval overlaps existing data")

        # Check for adjacency.  If there's a stream in the database
        # that ends exactly when this one starts, and the database
        # rows match up, we can make one interval that covers the
        # time range [adjacent.start -> interval.end)
        # and database rows [ adjacent.start_pos -> end_pos ].
        # Only do this if the resulting interval isn't too large.
        max_merged_rows = 8000 * 60 * 60 * 1.05 # 1.05 hours at 8 KHz
        adjacent = iset.find_end(interval.start)
        if (adjacent is not None and
            start_pos == adjacent.db_endpos and
            (end_pos - adjacent.db_startpos) < max_merged_rows):
            # First delete the old one, both from our iset and the
            # database
            iset -= adjacent
            self._sql_interval_delete(stream_id,
                                      adjacent.db_start, adjacent.db_end,
                                      adjacent.db_startpos, adjacent.db_endpos)

            # Now update our interval so the fallthrough add is
            # correct.
            interval.start = adjacent.start
            start_pos = adjacent.db_startpos

        # Add the new interval to the iset
        iset.iadd_nocheck(DBInterval(interval.start, interval.end,
                                     interval.start, interval.end,
                                     start_pos, end_pos))

        # Insert into the database
        self._sql_interval_insert(stream_id, interval.start, interval.end,
                                  int(start_pos), int(end_pos))

        self.con.commit()

    def _remove_interval(self, stream_id, original, remove):
        """
        Remove an interval from the internal cache and the database.

        stream_id: id of stream
         original: original DBInterval; must be already present in DB
        to_remove: DBInterval to remove; must be subset of 'original'
        """
        # Just return if we have nothing to remove
        if remove.start == remove.end: # pragma: no cover
            return

        # Load this stream's intervals
        iset = self._get_intervals(stream_id)

        # Remove existing interval from the cached set and the database
        iset -= original
        self._sql_interval_delete(stream_id,
                                  original.db_start, original.db_end,
                                  original.db_startpos, original.db_endpos)

        # Add back the intervals that would be left over if the
        # requested interval is removed.  There may be two of them, if
        # the removed piece was in the middle.
        def add(iset, start, end, start_pos, end_pos):
            iset += DBInterval(start, end, start, end, start_pos, end_pos)
            self._sql_interval_insert(stream_id, start, end, start_pos, end_pos)

        if original.start != remove.start:
            # Interval before the removed region
            add(iset, original.start, remove.start,
                original.db_startpos, remove.db_startpos)

        if original.end != remove.end:
            # Interval after the removed region
            add(iset, remove.end, original.end,
                remove.db_endpos, original.db_endpos)

        # Commit SQL changes
        self.con.commit()

        return

    def stream_list(self, path = None, layout = None):
        """Return list of [path, layout] lists of all streams
        in the database.

        If path is specified, include only streams with a path that
        matches the given string.

        If layout is specified, include only streams with a layout
        that matches the given string.
        """
        where = "WHERE 1=1"
        params = ()
        if layout:
            where += " AND layout=?"
            params += (layout,)
        if path:
            where += " AND path=?"
            params += (path,)
        result = self.con.execute("SELECT path, layout "
                                  "FROM streams " + where, params).fetchall()

        return sorted(list(x) for x in result)

    def stream_intervals(self, path, start = None, end = None):
        """
        Returns (intervals, restart) tuple.

        intervals is a list of [start,end] timestamps of all intervals
        that exist for path, between start and end.

        restart, if nonzero, means that there were too many results to
        return in a single request.  The data is complete from the
        starting timestamp to the point at which it was truncated,
        and a new request with a start time of 'restart' will fetch
        the next block of data.
        """
        stream_id = self._stream_id(path)
        intervals = self._get_intervals(stream_id)
        (start, end) = self._fill_in_limits(start, end)
        requested = Interval(start, end)
        result = []
        for n, i in enumerate(intervals.intersection(requested)):
            if n >= self.max_results:
                restart = i.start
                break
            result.append([i.start, i.end])
        else:
            restart = 0
        return (result, restart)

    def stream_create(self, path, layout_name):
        """Create a new table in the database.

        path: path to the data (e.g. '/newton/prep').
        Paths must contain at least two elements, e.g.:
           /newton/prep
           /newton/raw
           /newton/upstairs/prep
           /newton/upstairs/raw

        layout_name: string for nilmdb.layout.get_named(), e.g. 'float32_8'
        """
        # Create the bulk storage.  Raises ValueError on error, which we
        # pass along.
        self.data.create(path, layout_name)

        # Insert into SQL database once the bulk storage is happy
        with self.con as con:
            con.execute("INSERT INTO streams (path, layout) VALUES (?,?)",
                        (path, layout_name))

    def _stream_id(self, path):
        """Return unique stream ID"""
        result = self.con.execute("SELECT id FROM streams WHERE path=?",
                                  (path,)).fetchone()
        if result is None:
            raise StreamError("No stream at path " + path)
        return result[0]

    def stream_set_metadata(self, path, data):
        """Set stream metadata from a dictionary, e.g.
           { description = 'Downstairs lighting',
             v_scaling = 123.45 }
           This replaces all existing metadata.
           """
        stream_id = self._stream_id(path)
        with self.con as con:
            con.execute("DELETE FROM metadata WHERE stream_id=?", (stream_id,))
            for key in data:
                if data[key] != '':
                    con.execute("INSERT INTO metadata VALUES (?, ?, ?)",
                                (stream_id, key, data[key]))

    def stream_get_metadata(self, path):
        """Return stream metadata as a dictionary."""
        stream_id = self._stream_id(path)
        result = self.con.execute("SELECT metadata.key, metadata.value "
                                  "FROM metadata "
                                  "WHERE metadata.stream_id=?", (stream_id,))
        data = {}
        for (key, value) in result:
            data[key] = value
        return data

    def stream_update_metadata(self, path, newdata):
        """Update stream metadata from a dictionary"""
        data = self.stream_get_metadata(path)
        data.update(newdata)
        self.stream_set_metadata(path, data)

    def stream_destroy(self, path):
        """Fully remove a table and all of its data from the database.
        No way to undo it!  Metadata is removed."""
        stream_id = self._stream_id(path)

        # Delete the cached interval data (if it was cached)
        self._get_intervals.cache_remove(self, stream_id)

        # Delete the data
        self.data.destroy(path)

        # Delete metadata, stream, intervals
        with self.con as con:
            con.execute("DELETE FROM metadata WHERE stream_id=?", (stream_id,))
            con.execute("DELETE FROM ranges WHERE stream_id=?", (stream_id,))
            con.execute("DELETE FROM streams WHERE id=?", (stream_id,))

    def stream_insert(self, path, start, end, data):
        """Insert new data into the database.
           path: Path at which to add the data
           start: Starting timestamp
           end: Ending timestamp
           data: Rows of data, to be passed to bulkdata table.append
                 method.  E.g. nilmdb.layout.Parser.data
           """
        # First check for basic overlap using timestamp info given.
        stream_id = self._stream_id(path)
        iset = self._get_intervals(stream_id)
        interval = Interval(start, end)
        if iset.intersects(interval):
            raise OverlapError("new data overlaps existing data at range: "
                               + str(iset & interval))

        # Insert the data
        table = self.data.getnode(path)
        row_start = table.nrows
        table.append(data)
        row_end = table.nrows

        # Insert the record into the sql database.
        self._add_interval(stream_id, interval, row_start, row_end)

        # And that's all
        return

    def _find_start(self, table, dbinterval):
        """
        Given a DBInterval, find the row in the database that
        corresponds to the start time.  Return the first database
        position with a timestamp (first element) greater than or
        equal to 'start'.
        """
        # Optimization for the common case where an interval wasn't truncated
        if dbinterval.start == dbinterval.db_start:
            return dbinterval.db_startpos
        return bisect.bisect_left(bulkdata.TimestampOnlyTable(table),
                                  dbinterval.start,
                                  dbinterval.db_startpos,
                                  dbinterval.db_endpos)

    def _find_end(self, table, dbinterval):
        """
        Given a DBInterval, find the row in the database that follows
        the end time.  Return the first database position after the
        row with timestamp (first element) greater than or equal
        to 'end'.
        """
        # Optimization for the common case where an interval wasn't truncated
        if dbinterval.end == dbinterval.db_end:
            return dbinterval.db_endpos
        # Note that we still use bisect_left here, because we don't
        # want to include the given timestamp in the results.  This is
        # so a queries like 1:00 -> 2:00 and 2:00 -> 3:00 return
        # non-overlapping data.
        return bisect.bisect_left(bulkdata.TimestampOnlyTable(table),
                                  dbinterval.end,
                                  dbinterval.db_startpos,
                                  dbinterval.db_endpos)

    def stream_extract(self, path, start = None, end = None, count = False):
        """
        Returns (data, restart) tuple.

        data is a list of raw data from the database, suitable for
        passing to e.g. nilmdb.layout.Formatter to translate into
        textual form.

        restart, if nonzero, means that there were too many results to
        return in a single request.  The data is complete from the
        starting timestamp to the point at which it was truncated,
        and a new request with a start time of 'restart' will fetch
        the next block of data.

        count, if true, means to not return raw data, but just the count
        of rows that would have been returned.  This is much faster
        than actually fetching the data.  It is not limited by
        max_results.
        """
        stream_id = self._stream_id(path)
        table = self.data.getnode(path)
        intervals = self._get_intervals(stream_id)
        (start, end) = self._fill_in_limits(start, end)
        requested = Interval(start, end)
        result = []
        matched = 0
        remaining = self.max_results
        restart = 0
        for interval in intervals.intersection(requested):
            # Reading single rows from the table is too slow, so
            # we use two bisections to find both the starting and
            # ending row for this particular interval, then
            # read the entire range as one slice.
            row_start = self._find_start(table, interval)
            row_end = self._find_end(table, interval)

            if count:
                matched += row_end - row_start
                continue

            # Shorten it if we'll hit the maximum number of results
            row_max = row_start + remaining
            if row_max < row_end:
                row_end = row_max
                restart = table[row_max][0]

            # Gather these results up
            result.extend(table[row_start:row_end])

            # Count them
            remaining -= row_end - row_start

            if restart:
                break

        if count:
            return matched
        return (result, restart)

    def stream_remove(self, path, start = None, end = None):
        """
        Remove data from the specified time interval within a stream.
        Removes all data in the interval [start, end), and intervals
        are truncated or split appropriately.  Returns the number of
        data points removed.
        """
        stream_id = self._stream_id(path)
        table = self.data.getnode(path)
        intervals = self._get_intervals(stream_id)
        (start, end) = self._fill_in_limits(start, end)
        to_remove = Interval(start, end)
        removed = 0

        # Can't remove intervals from within the iterator, so we need to
        # remember what's currently in the intersection now.
        all_candidates = list(intervals.intersection(to_remove, orig = True))

        for (dbint, orig) in all_candidates:
            # Find row start and end
            row_start = self._find_start(table, dbint)
            row_end = self._find_end(table, dbint)

            # Adjust the DBInterval to match the newly found ends
            dbint.db_start = dbint.start
            dbint.db_end = dbint.end
            dbint.db_startpos = row_start
            dbint.db_endpos = row_end

            # Remove interval from the database
            self._remove_interval(stream_id, orig, dbint)

            # Remove data from the underlying table storage
            table.remove(row_start, row_end)

            # Count how many were removed
            removed += row_end - row_start

        return removed