sqlglot.helper

  1from __future__ import annotations
  2
  3import inspect
  4import logging
  5import re
  6import sys
  7import typing as t
  8from collections.abc import Collection
  9from contextlib import contextmanager
 10from copy import copy
 11from enum import Enum
 12from itertools import count
 13
 14if t.TYPE_CHECKING:
 15    from sqlglot import exp
 16    from sqlglot._typing import E, T
 17    from sqlglot.expressions import Expression
 18
 19CAMEL_CASE_PATTERN = re.compile("(?<!^)(?=[A-Z])")
 20PYTHON_VERSION = sys.version_info[:2]
 21logger = logging.getLogger("sqlglot")
 22
 23
 24class AutoName(Enum):
 25    """
 26    This is used for creating Enum classes where `auto()` is the string form
 27    of the corresponding enum's identifier (e.g. FOO.value results in "FOO").
 28
 29    Reference: https://docs.python.org/3/howto/enum.html#using-automatic-values
 30    """
 31
 32    def _generate_next_value_(name, _start, _count, _last_values):
 33        return name
 34
 35
 36class classproperty(property):
 37    """
 38    Similar to a normal property but works for class methods
 39    """
 40
 41    def __get__(self, obj: t.Any, owner: t.Any = None) -> t.Any:
 42        return classmethod(self.fget).__get__(None, owner)()  # type: ignore
 43
 44
 45def seq_get(seq: t.Sequence[T], index: int) -> t.Optional[T]:
 46    """Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds."""
 47    try:
 48        return seq[index]
 49    except IndexError:
 50        return None
 51
 52
 53@t.overload
 54def ensure_list(value: t.Collection[T]) -> t.List[T]:
 55    ...
 56
 57
 58@t.overload
 59def ensure_list(value: T) -> t.List[T]:
 60    ...
 61
 62
 63def ensure_list(value):
 64    """
 65    Ensures that a value is a list, otherwise casts or wraps it into one.
 66
 67    Args:
 68        value: The value of interest.
 69
 70    Returns:
 71        The value cast as a list if it's a list or a tuple, or else the value wrapped in a list.
 72    """
 73    if value is None:
 74        return []
 75    if isinstance(value, (list, tuple)):
 76        return list(value)
 77
 78    return [value]
 79
 80
 81@t.overload
 82def ensure_collection(value: t.Collection[T]) -> t.Collection[T]:
 83    ...
 84
 85
 86@t.overload
 87def ensure_collection(value: T) -> t.Collection[T]:
 88    ...
 89
 90
 91def ensure_collection(value):
 92    """
 93    Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.
 94
 95    Args:
 96        value: The value of interest.
 97
 98    Returns:
 99        The value if it's a collection, or else the value wrapped in a list.
100    """
101    if value is None:
102        return []
103    return (
104        value if isinstance(value, Collection) and not isinstance(value, (str, bytes)) else [value]
105    )
106
107
108def csv(*args: str, sep: str = ", ") -> str:
109    """
110    Formats any number of string arguments as CSV.
111
112    Args:
113        args: The string arguments to format.
114        sep: The argument separator.
115
116    Returns:
117        The arguments formatted as a CSV string.
118    """
119    return sep.join(arg for arg in args if arg)
120
121
122def subclasses(
123    module_name: str,
124    classes: t.Type | t.Tuple[t.Type, ...],
125    exclude: t.Type | t.Tuple[t.Type, ...] = (),
126) -> t.List[t.Type]:
127    """
128    Returns all subclasses for a collection of classes, possibly excluding some of them.
129
130    Args:
131        module_name: The name of the module to search for subclasses in.
132        classes: Class(es) we want to find the subclasses of.
133        exclude: Class(es) we want to exclude from the returned list.
134
135    Returns:
136        The target subclasses.
137    """
138    return [
139        obj
140        for _, obj in inspect.getmembers(
141            sys.modules[module_name],
142            lambda obj: inspect.isclass(obj) and issubclass(obj, classes) and obj not in exclude,
143        )
144    ]
145
146
147def apply_index_offset(
148    this: exp.Expression,
149    expressions: t.List[E],
150    offset: int,
151) -> t.List[E]:
152    """
153    Applies an offset to a given integer literal expression.
154
155    Args:
156        this: The target of the index.
157        expressions: The expression the offset will be applied to, wrapped in a list.
158        offset: The offset that will be applied.
159
160    Returns:
161        The original expression with the offset applied to it, wrapped in a list. If the provided
162        `expressions` argument contains more than one expression, it's returned unaffected.
163    """
164    if not offset or len(expressions) != 1:
165        return expressions
166
167    expression = expressions[0]
168
169    from sqlglot import exp
170    from sqlglot.optimizer.annotate_types import annotate_types
171    from sqlglot.optimizer.simplify import simplify
172
173    if not this.type:
174        annotate_types(this)
175
176    if t.cast(exp.DataType, this.type).this not in (
177        exp.DataType.Type.UNKNOWN,
178        exp.DataType.Type.ARRAY,
179    ):
180        return expressions
181
182    if not expression.type:
183        annotate_types(expression)
184    if t.cast(exp.DataType, expression.type).this in exp.DataType.INTEGER_TYPES:
185        logger.warning("Applying array index offset (%s)", offset)
186        expression = simplify(
187            exp.Add(this=expression.copy(), expression=exp.Literal.number(offset))
188        )
189        return [expression]
190
191    return expressions
192
193
194def camel_to_snake_case(name: str) -> str:
195    """Converts `name` from camelCase to snake_case and returns the result."""
196    return CAMEL_CASE_PATTERN.sub("_", name).upper()
197
198
199def while_changing(expression: Expression, func: t.Callable[[Expression], E]) -> E:
200    """
201    Applies a transformation to a given expression until a fix point is reached.
202
203    Args:
204        expression: The expression to be transformed.
205        func: The transformation to be applied.
206
207    Returns:
208        The transformed expression.
209    """
210    while True:
211        for n, *_ in reversed(tuple(expression.walk())):
212            n._hash = hash(n)
213
214        start = hash(expression)
215        expression = func(expression)
216
217        for n, *_ in expression.walk():
218            n._hash = None
219        if start == hash(expression):
220            break
221
222    return expression
223
224
225def tsort(dag: t.Dict[T, t.Set[T]]) -> t.List[T]:
226    """
227    Sorts a given directed acyclic graph in topological order.
228
229    Args:
230        dag: The graph to be sorted.
231
232    Returns:
233        A list that contains all of the graph's nodes in topological order.
234    """
235    result = []
236
237    for node, deps in tuple(dag.items()):
238        for dep in deps:
239            if not dep in dag:
240                dag[dep] = set()
241
242    while dag:
243        current = {node for node, deps in dag.items() if not deps}
244
245        if not current:
246            raise ValueError("Cycle error")
247
248        for node in current:
249            dag.pop(node)
250
251        for deps in dag.values():
252            deps -= current
253
254        result.extend(sorted(current))  # type: ignore
255
256    return result
257
258
259def open_file(file_name: str) -> t.TextIO:
260    """Open a file that may be compressed as gzip and return it in universal newline mode."""
261    with open(file_name, "rb") as f:
262        gzipped = f.read(2) == b"\x1f\x8b"
263
264    if gzipped:
265        import gzip
266
267        return gzip.open(file_name, "rt", newline="")
268
269    return open(file_name, encoding="utf-8", newline="")
270
271
272@contextmanager
273def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
274    """
275    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
276
277    Args:
278        read_csv: A `ReadCSV` function call.
279
280    Yields:
281        A python csv reader.
282    """
283    args = read_csv.expressions
284    file = open_file(read_csv.name)
285
286    delimiter = ","
287    args = iter(arg.name for arg in args)
288    for k, v in zip(args, args):
289        if k == "delimiter":
290            delimiter = v
291
292    try:
293        import csv as csv_
294
295        yield csv_.reader(file, delimiter=delimiter)
296    finally:
297        file.close()
298
299
300def find_new_name(taken: t.Collection[str], base: str) -> str:
301    """
302    Searches for a new name.
303
304    Args:
305        taken: A collection of taken names.
306        base: Base name to alter.
307
308    Returns:
309        The new, available name.
310    """
311    if base not in taken:
312        return base
313
314    i = 2
315    new = f"{base}_{i}"
316    while new in taken:
317        i += 1
318        new = f"{base}_{i}"
319
320    return new
321
322
323def name_sequence(prefix: str) -> t.Callable[[], str]:
324    """Returns a name generator given a prefix (e.g. a0, a1, a2, ... if the prefix is "a")."""
325    sequence = count()
326    return lambda: f"{prefix}{next(sequence)}"
327
328
329def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
330    """Returns a dictionary created from an object's attributes."""
331    return {
332        **{k: v.copy() if hasattr(v, "copy") else copy(v) for k, v in vars(obj).items()},
333        **kwargs,
334    }
335
336
337def split_num_words(
338    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
339) -> t.List[t.Optional[str]]:
340    """
341    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
342
343    Args:
344        value: The value to be split.
345        sep: The value to use to split on.
346        min_num_words: The minimum number of words that are going to be in the result.
347        fill_from_start: Indicates that if `None` values should be inserted at the start or end of the list.
348
349    Examples:
350        >>> split_num_words("db.table", ".", 3)
351        [None, 'db', 'table']
352        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
353        ['db', 'table', None]
354        >>> split_num_words("db.table", ".", 1)
355        ['db', 'table']
356
357    Returns:
358        The list of words returned by `split`, possibly augmented by a number of `None` values.
359    """
360    words = value.split(sep)
361    if fill_from_start:
362        return [None] * (min_num_words - len(words)) + words
363    return words + [None] * (min_num_words - len(words))
364
365
366def is_iterable(value: t.Any) -> bool:
367    """
368    Checks if the value is an iterable, excluding the types `str` and `bytes`.
369
370    Examples:
371        >>> is_iterable([1,2])
372        True
373        >>> is_iterable("test")
374        False
375
376    Args:
377        value: The value to check if it is an iterable.
378
379    Returns:
380        A `bool` value indicating if it is an iterable.
381    """
382    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes))
383
384
385def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
386    """
387    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
388    type `str` and `bytes` are not regarded as iterables.
389
390    Examples:
391        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
392        [1, 2, 3, 4, 5, 'bla']
393        >>> list(flatten([1, 2, 3]))
394        [1, 2, 3]
395
396    Args:
397        values: The value to be flattened.
398
399    Yields:
400        Non-iterable elements in `values`.
401    """
402    for value in values:
403        if is_iterable(value):
404            yield from flatten(value)
405        else:
406            yield value
407
408
409def dict_depth(d: t.Dict) -> int:
410    """
411    Get the nesting depth of a dictionary.
412
413    Example:
414        >>> dict_depth(None)
415        0
416        >>> dict_depth({})
417        1
418        >>> dict_depth({"a": "b"})
419        1
420        >>> dict_depth({"a": {}})
421        2
422        >>> dict_depth({"a": {"b": {}}})
423        3
424    """
425    try:
426        return 1 + dict_depth(next(iter(d.values())))
427    except AttributeError:
428        # d doesn't have attribute "values"
429        return 0
430    except StopIteration:
431        # d.values() returns an empty sequence
432        return 1
433
434
435def first(it: t.Iterable[T]) -> T:
436    """Returns the first element from an iterable (useful for sets)."""
437    return next(i for i in it)