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apdbMetadataSql.py
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1# This file is part of dax_apdb.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
13#
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
18#
19# You should have received a copy of the GNU General Public License
20# along with this program. If not, see <http://www.gnu.org/licenses/>.
21
22from __future__ import annotations
23
24__all__ = ["ApdbMetadataSql"]
25
26from collections.abc import Generator
27
28import sqlalchemy
29
30from ..apdbMetadata import ApdbMetadata
31
32
34 """Implementation of `ApdbMetadata` for SQL backend.
35
36 Parameters
37 ----------
38 engine : `sqlalchemy.engine.Engine`
39 Database access engine.
40 table : `sqlalchemy.schema.Table` or `None`
41 Database table holding metadata. If table does not exists then `None`
42 should be specified.
43 """
44
45 def __init__(self, engine: sqlalchemy.engine.Engine, table: sqlalchemy.schema.Table | None):
46 self._engine = engine
47 self._table = table
48
49 def get(self, key: str, default: str | None = None) -> str | None:
50 # Docstring is inherited.
51 if self._table is None:
52 return default
53 sql = sqlalchemy.sql.select(self._table.columns.value).where(self._table.columns.name == key)
54 with self._engine.begin() as conn:
55 result = conn.execute(sql)
56 value = result.scalar()
57 if value is not None:
58 return value
59 return default
60
61 def set(self, key: str, value: str, *, force: bool = False) -> None:
62 # Docstring is inherited.
63 if self._table is None:
64 raise RuntimeError("Metadata table does not exist")
65 if not key or not value:
66 raise ValueError("name and value cannot be empty")
67 try:
68 insert = sqlalchemy.sql.insert(self._table).values(name=key, value=value)
69 with self._engine.begin() as conn:
70 conn.execute(insert)
71 except sqlalchemy.exc.IntegrityError as exc:
72 # Try to update if it exists.
73 if not force:
74 raise KeyError(f"Metadata key {key!r} already exists") from exc
75 update = (
76 sqlalchemy.sql.update(self._table).where(self._table.columns.name == key).values(value=value)
77 )
78 with self._engine.begin() as conn:
79 result = conn.execute(update)
80 if result.rowcount != 1:
81 raise RuntimeError(f"Metadata update failed unexpectedly, count={result.rowcount}")
82
83 def delete(self, key: str) -> bool:
84 # Docstring is inherited.
85 if self._table is None:
86 # Missing table means nothing to delete.
87 return False
88 stmt = sqlalchemy.sql.delete(self._table).where(self._table.columns.name == key)
89 with self._engine.begin() as conn:
90 result = conn.execute(stmt)
91 return result.rowcount > 0
92
93 def items(self) -> Generator[tuple[str, str], None, None]:
94 # Docstring is inherited.
95 if self._table is None:
96 # Missing table means nothing to return.
97 return
98 stmt = sqlalchemy.sql.select(self._table.columns.name, self._table.columns.value)
99 with self._engine.begin() as conn:
100 result = conn.execute(stmt)
101 for row in result:
102 yield row._tuple()
103
104 def empty(self) -> bool:
105 # Docstring is inherited.
106 if self._table is None:
107 # Missing table means empty.
108 return True
109 stmt = sqlalchemy.sql.select(sqlalchemy.sql.func.count()).select_from(self._table)
110 with self._engine.begin() as conn:
111 result = conn.execute(stmt)
112 count = result.scalar()
113 return count == 0
114
115 def table_exists(self) -> bool:
116 """Return `True` if metadata table exists."""
117 return self._table is not None
__init__(self, sqlalchemy.engine.Engine engine, sqlalchemy.schema.Table|None table)
None set(self, str key, str value, *, bool force=False)
str|None get(self, str key, str|None default=None)
Generator[tuple[str, str], None, None] items(self)