def _read_metadata(self):
""" return the meta table """
self.ensure_bank_path_exists()
with sql_connection(self.index_path) as con:
sql = f'SELECT * FROM "{self._meta_node}";'
out = pd.read_sql(sql, con)
return out
def read_index(self, **kwargs) -> pd.DataFrame:
"""
Read the index and return a dataframe containing the event info.
Parameters
----------
{get_events_params}
"""
self.ensure_bank_path_exists()
# Make sure all times are numpy datetime64
kwargs = _dict_times_to_npdatetimes(kwargs)
# a simple switch to prevent infinite recursion
allow_update = kwargs.pop("_allow_update", True)
# Circular search requires work to be done on the dataframe - we need
# to get the whole dataframe then calculate the distances and search in
# that
circular_kwargs, kwargs = _sanitize_circular_search(**kwargs)
with sql_connection(self.index_path) as con:
try:
df = _read_table(self._index_node, con, **kwargs)
except pd.io.sql.DatabaseError:
# if this database has never been updated, update now
if allow_update and self.last_updated_timestamp < 1:
self.update_index()
return self.read_index(_allow_update=False, **kwargs)
# else return empty index
df = pd.DataFrame(columns=list(EVENT_TYPES_OUTPUT))
df = _ints_to_time_columns(df, columns=INT_COLUMNS).pipe(
self._prepare_dataframe, dtypes=EVENT_TYPES_OUTPUT)
if len(circular_kwargs) >= 3:
# Requires at least latitude, longitude and min or max radius
circular_ids = _get_ids(df, circular_kwargs)
df = df[df.event_id.isin(circular_ids)]
return df
def _write_update(self, df: pd.DataFrame, update_time=None):
""" convert updates to dataframe, then append to index table """
# read in dataframe and cast to correct types
assert not df.duplicated().any(), "update index has duplicate entries"
# set both dfs to use index of event_id
df = df.set_index("event_id")
# get current events, but dont allow it to update again
current = self.read_index(event_id=set(df.index), _allow_update=False)
indicies_to_update = set(current["event_id"]) & set(df.index)
# populate index store and update metadata
with sql_connection(self.index_path) as con:
if indicies_to_update: # delete rows that will be re-entered
_drop_rows(self._index_node, con, event_id=indicies_to_update)
node = self._index_node
df.to_sql(node, con, if_exists="append", index_label="event_id")
tables = _get_tables(con)
if self._meta_node not in tables:
meta = self._make_meta_table()
meta.to_sql(self._meta_node, con, if_exists="replace")
# update timestamp
with suppress_warnings(): # ignore pandas collection warning
if self.allow_update_timestamp:
timestamp = update_time or time.time()
dft = pd.DataFrame(timestamp, index=[0], columns=["time"])
dft.to_sql(self._time_node,
con,
if_exists="replace",
index=False)
self._metadata = meta
self._index = None
def last_updated_timestamp(self):
""" Return the last modified time stored in the index, else 0.0 """
with sql_connection(self.index_path) as con:
try:
return _read_table(self._time_node, con).loc[0, "time"]
except (pd.io.sql.DatabaseError, KeyError): # table is empty
return 0.0