Inheritance diagram for lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra:
Public Member Functions | |
| __init__ (self, Any session, str table_name, str keyspace, str read_profile, str write_profile) | |
| str|None | get (self, str key, str|None default=None) |
| None | set (self, str key, str value, *bool force=False) |
| bool | delete (self, str key) |
| Generator[tuple[str, str], None, None] | items (self) |
| bool | empty (self) |
| bool | table_exists (self) |
Protected Attributes | |
| _session | |
| _read_profile | |
| _write_profile | |
| _part | |
| _preparer | |
| _table_clause | |
Detailed Description
Implementation of `ApdbMetadata` for Cassandra backend.
Parameters
----------
session : `cassandra.cluster.Session`
Cassandra session instance.
schema : `ApdbSqlSchema`
Object providing access to schema details.
Definition at line 33 of file apdbMetadataCassandra.py.
Constructor & Destructor Documentation
◆ __init__()
| lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.__init__ | ( | self, | |
| Any | session, | ||
| str | table_name, | ||
| str | keyspace, | ||
| str | read_profile, | ||
| str | write_profile ) |
Definition at line 44 of file apdbMetadataCassandra.py.
44 def __init__(self, session: Any, table_name: str, keyspace: str, read_profile: str, write_profile: str):
45 self._session = session
46 self._read_profile = read_profile
47 self._write_profile = write_profile
48 self._part = 0 # Partition for all rows
49 self._preparer = PreparedStatementCache(session)
50 # _table_clause will be None when metadata table is not configured
51 self._table_clause: str | None = None
52
53 query = "SELECT count(*) FROM system_schema.tables WHERE keyspace_name = %s and table_name = %s"
54 result = self._session.execute(query, (keyspace, table_name), execution_profile=read_profile)
55 exists = bool(result.one()[0])
56 if exists:
57 self._table_clause = f"{quote_id(keyspace)}.{quote_id(table_name)}"
58
Member Function Documentation
◆ delete()
| bool lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.delete | ( | self, | |
| str | key ) |
Delete metadata record.
Parameters
----------
key : `str`
Metadata key, arbitrary non-empty string.
Returns
-------
existed : `bool`
`True` is returned if attribute existed before it was deleted.
Reimplemented from lsst.dax.apdb.apdbMetadata.ApdbMetadata.
Definition at line 86 of file apdbMetadataCassandra.py.
86 def delete(self, key: str) -> bool:
87 # Docstring is inherited.
88 if self._table_clause is None:
89 # Missing table means nothing to delete.
90 return False
91 if not key:
92 raise ValueError("name cannot be empty")
93 query = f"DELETE FROM {self._table_clause} WHERE meta_part = ? AND name = ?"
94 # Cassandra cannot tell how many rows are deleted, just check if row
95 # exists now.
96 exists = self.get(key) is not None
97 # Race is still possible between check and remove.
98 self._session.execute(
99 self._preparer.prepare(query), (self._part, key), execution_profile=self._write_profile
100 )
101 return exists
102
◆ empty()
| bool lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.empty | ( | self | ) |
Check whether attributes set is empty.
Returns
-------
empty : `bool`
`True` if there are no any attributes defined. `True` is also
returned if metadata table is missing.
Reimplemented from lsst.dax.apdb.apdbMetadata.ApdbMetadata.
Definition at line 115 of file apdbMetadataCassandra.py.
115 def empty(self) -> bool:
116 # Docstring is inherited.
117 if self._table_clause is None:
118 # Missing table means empty.
119 return True
120 query = f"SELECT count(*) FROM {self._table_clause} WHERE meta_part = ?"
121 result = self._session.execute(
122 self._preparer.prepare(query), (self._part,), execution_profile=self._read_profile
123 )
124 row = result.one()
125 return row[0] == 0
126
◆ get()
| str | None lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.get | ( | self, | |
| str | key, | ||
| str | None | default = None ) |
Retrieve value of a given metadata record.
Parameters
----------
key : `str`
Metadata key, arbitrary non-empty string.
default : `str`, optional
Default value returned when key does not exist, can be string
or `None`.
Returns
-------
value : `str` or `None`
Metadata value, if key does not exist then ``default`` is returned.
Reimplemented from lsst.dax.apdb.apdbMetadata.ApdbMetadata.
Definition at line 59 of file apdbMetadataCassandra.py.
59 def get(self, key: str, default: str | None = None) -> str | None:
60 # Docstring is inherited.
61 if self._table_clause is None:
62 return default
63 query = f"SELECT value FROM {self._table_clause} WHERE meta_part = ? AND name = ?"
64 result = self._session.execute(
65 self._preparer.prepare(query), (self._part, key), execution_profile=self._read_profile
66 )
67 if (row := result.one()) is not None:
68 return row[0]
69 else:
70 return default
71
◆ items()
| Generator[tuple[str, str], None, None] lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.items | ( | self | ) |
Iterate over records and yield their keys and values.
Yields
------
key : `str`
Metadata key.
value : `str`
Corresponding metadata value.
Reimplemented from lsst.dax.apdb.apdbMetadata.ApdbMetadata.
Definition at line 103 of file apdbMetadataCassandra.py.
104 # Docstring is inherited.
105 if self._table_clause is None:
106 # Missing table means nothing to return.
107 return
108 query = f"SELECT name, value FROM {self._table_clause} WHERE meta_part = ?"
109 result = self._session.execute(
110 self._preparer.prepare(query), (self._part,), execution_profile=self._read_profile
111 )
112 for row in result:
113 yield tuple(row)
114
◆ set()
| None lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.set | ( | self, | |
| str | key, | ||
| str | value, | ||
| *bool | force = False ) |
Set value for a given metadata record.
Parameters
----------
key : `str`
Metadata key, arbitrary non-empty string.
value : `str`
New metadata value, an arbitrary string. Due to deficiencies of
some database engines we are not allowing empty strings to be
stored in the database, and ``value`` cannot be an empty string.
force : `bool`, optional
Controls handling of existing metadata. With default `False`
value an exception is raised if ``key`` already exists, if `True`
is passed then value of the existing key will be updated.
Raises
------
KeyError
Raised if key already exists but ``force`` option is false.
ValueError
Raised if key or value parameters are empty.
Reimplemented from lsst.dax.apdb.apdbMetadata.ApdbMetadata.
Definition at line 72 of file apdbMetadataCassandra.py.
73 # Docstring is inherited.
74 if self._table_clause is None:
75 raise RuntimeError("Metadata table does not exist")
76 if not key or not value:
77 raise ValueError("name and value cannot be empty")
78 query = f"INSERT INTO {self._table_clause} (meta_part, name, value) VALUES (?, ?, ?)"
79 if not force and self.get(key) is not None:
80 raise KeyError(f"Metadata key {key!r} already exists")
81 # Race is still possible between check and insert.
82 self._session.execute(
83 self._preparer.prepare(query), (self._part, key, value), execution_profile=self._write_profile
84 )
85
◆ table_exists()
| bool lsst.dax.apdb.apdbMetadataCassandra.ApdbMetadataCassandra.table_exists | ( | self | ) |
Return `True` if metadata table exists.
Definition at line 127 of file apdbMetadataCassandra.py.
127 def table_exists(self) -> bool:
128 """Return `True` if metadata table exists."""
129 return self._table_clause is not None
Member Data Documentation
◆ _part
|
protected |
Definition at line 48 of file apdbMetadataCassandra.py.
◆ _preparer
|
protected |
Definition at line 49 of file apdbMetadataCassandra.py.
◆ _read_profile
|
protected |
Definition at line 46 of file apdbMetadataCassandra.py.
◆ _session
|
protected |
Definition at line 45 of file apdbMetadataCassandra.py.
◆ _table_clause
|
protected |
Definition at line 57 of file apdbMetadataCassandra.py.
◆ _write_profile
|
protected |
Definition at line 47 of file apdbMetadataCassandra.py.
The documentation for this class was generated from the following file:
- /j/snowflake/release/lsstsw/stack/lsst-scipipe-8.0.0/Linux64/dax_apdb/gd2a12a3803+f8351bc914/python/lsst/dax/apdb/apdbMetadataCassandra.py
