#!/usr/bin/env python
# cardinal_pythonlib/sql/literals.py
"""
===============================================================================
Original code copyright (C) 2009-2022 Rudolf Cardinal (rudolf@pobox.com).
This file is part of cardinal_pythonlib.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
https://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
===============================================================================
**Functions to manipulate raw SQL.**
"""
from typing import Generator
from cardinal_pythonlib.datetimefunc import DateLikeType, DateTimeLikeType
COMMA = ","
SQUOTE = "'"
DOUBLE_SQUOTE = "''"
# =============================================================================
# SQL elements: literals
# =============================================================================
[docs]def sql_string_literal(text: str) -> str:
"""
Transforms text into its ANSI SQL-quoted version, e.g. (in Python
``repr()`` format):
.. code-block:: none
"some string" -> "'some string'"
"Jack's dog" -> "'Jack''s dog'"
"""
# ANSI SQL: http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt
# <character string literal>
return SQUOTE + text.replace(SQUOTE, DOUBLE_SQUOTE) + SQUOTE
sql_quote_string = sql_string_literal # synonym
[docs]def sql_date_literal(dt: DateLikeType) -> str:
"""
Transforms a Python object that is of duck type ``datetime.date`` into
an ANSI SQL literal string, like '2000-12-31'.
"""
# ANSI SQL: http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt
# <date string>
return dt.strftime("'%Y-%m-%d'")
[docs]def sql_datetime_literal(dt: DateTimeLikeType, subsecond: bool = False) -> str:
"""
Transforms a Python object that is of duck type ``datetime.datetime`` into
an ANSI SQL literal string, like ``'2000-12-31 23:59:59'``, or if
``subsecond=True``, into the (non-ANSI) format
``'2000-12-31 23:59:59.123456'`` or similar.
"""
# ANSI SQL: http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt
# <timestamp string>
# ... the subsecond part is non-ANSI
fmt = "'%Y-%m-%d %H:%M:%S{}'".format(".%f" if subsecond else "")
return dt.strftime(fmt)
# =============================================================================
# Reversing the operations above
# =============================================================================
[docs]def sql_dequote_string(s: str) -> str:
"""
Reverses :func:`sql_quote_string`.
"""
if len(s) < 2 or s[0] != SQUOTE or s[-1] != SQUOTE:
raise ValueError("Not an SQL string literal")
s = s[1:-1] # strip off the surrounding quotes
return s.replace(DOUBLE_SQUOTE, SQUOTE)
# =============================================================================
# Processing SQL CSV values
# =============================================================================
[docs]def gen_items_from_sql_csv(s: str) -> Generator[str, None, None]:
"""
Splits a comma-separated list of quoted SQL values, with ``'`` as the quote
character. Allows escaping of the quote character by doubling it. Returns
the quotes (and escaped quotes) as part of the result. Allows newlines etc.
within the string passed.
"""
# csv.reader will not both process the quotes and return the quotes;
# we need them to distinguish e.g. NULL from 'NULL'.
# log.warning('gen_items_from_sql_csv: s = {0!r}', s)
if not s:
return
n = len(s)
startpos = 0
pos = 0
in_quotes = False
while pos < n:
if not in_quotes:
if s[pos] == COMMA:
# end of chunk
chunk = s[startpos:pos] # does not include s[pos]
result = chunk.strip()
# log.warning('yielding: {0!r}', result)
yield result
startpos = pos + 1
elif s[pos] == SQUOTE:
# start of quote
in_quotes = True
else:
if pos < n - 1 and s[pos] == SQUOTE and s[pos + 1] == SQUOTE:
# double quote, '', is an escaped quote, not end of quote
pos += 1 # skip one more than we otherwise would
elif s[pos] == SQUOTE:
# end of quote
in_quotes = False
pos += 1
# Last chunk
result = s[startpos:].strip()
# log.warning('yielding last: {0!r}', result)
yield result