"""
This module takes care of the SQLite settings.
"""
from __future__ import annotations
import sqlite3
def _read_settings() -> tuple[dict[str, str | int], dict[str, bool | int | str]]:
"""
Function to read the local SQLite settings at import time.
We mainly care about the SQLite limits, since these play a role
when committing large amounts of data to the DB, but we record
everything for good measures.
Returns:
Two dictionaries, one with the limits, one with all other settings.
If a setting has a value, that value is provided. Else a boolean
indicating wether SQLite was compiled with that option. A missing
option, say, 'FOOBAR' is equivalent to {'FOOBAR': False}.
"""
# For the limits, there are known default values
# (known from https://www.sqlite.org/limits.html)
DEFAULT_LIMITS: dict[str, str | int]
DEFAULT_LIMITS = {'MAX_ATTACHED': 10,
'MAX_COLUMN': 2000,
'MAX_COMPOUND_SELECT': 500,
'MAX_EXPR_DEPTH': 1000,
'MAX_FUNCTION_ARG': 100,
'MAX_LENGTH': 1_000_000_000,
'MAX_LIKE_PATTERN_LENGTH': 50_000,
'MAX_PAGE_COUNT': 1_073_741_823,
'MAX_SQL_LENGTH': 1_000_000,
'MAX_VARIABLE_NUMBER': 999}
conn = sqlite3.connect(':memory:')
c = conn.cursor()
opt_num = 0
resp = ''
limits: dict[str, str | int]
limits = DEFAULT_LIMITS.copy()
settings = {}
c.execute(f'select sqlite_compileoption_get({opt_num});')
resp = c.fetchone()[0]
# SQLite only responds back what options have been changed from
# the default, so we can't know a priori how many responses we'll get
while resp is not None:
opt_num += 1
lst = resp.split('=')
val: str | int | None
if len(lst) == 2:
(param, val_str) = lst
if val_str.isnumeric():
val = int(val_str)
else:
val = val_str
else:
param = lst[0]
val = None
if param in DEFAULT_LIMITS.keys():
# we are only expecting
# None val for a setting
assert val is not None
limits.update({param: val})
elif val:
settings.update({param: val})
else:
settings.update({param: True})
c.execute(f'select sqlite_compileoption_get({opt_num});')
resp = c.fetchone()[0]
c.execute('select sqlite_version();')
resp = c.fetchone()[0]
settings.update({'VERSION': resp})
c.close()
return (limits, settings)
[docs]
class SQLiteSettings:
"""
Class that holds the machine's sqlite options.
Note that the settings are not dynamically updated, so changes
during runtime must be updated manually. But you probably should not
be changing these settings dynamically in the first place.
"""
limits, settings = _read_settings()