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 A, E, T
 17    from sqlglot.expressions import Expression
 18
 19
 20CAMEL_CASE_PATTERN = re.compile("(?<!^)(?=[A-Z])")
 21PYTHON_VERSION = sys.version_info[:2]
 22logger = logging.getLogger("sqlglot")
 23
 24
 25class AutoName(Enum):
 26    """
 27    This is used for creating Enum classes where `auto()` is the string form
 28    of the corresponding enum's identifier (e.g. FOO.value results in "FOO").
 29
 30    Reference: https://docs.python.org/3/howto/enum.html#using-automatic-values
 31    """
 32
 33    def _generate_next_value_(name, _start, _count, _last_values):
 34        return name
 35
 36
 37class classproperty(property):
 38    """
 39    Similar to a normal property but works for class methods
 40    """
 41
 42    def __get__(self, obj: t.Any, owner: t.Any = None) -> t.Any:
 43        return classmethod(self.fget).__get__(None, owner)()  # type: ignore
 44
 45
 46def seq_get(seq: t.Sequence[T], index: int) -> t.Optional[T]:
 47    """Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds."""
 48    try:
 49        return seq[index]
 50    except IndexError:
 51        return None
 52
 53
 54@t.overload
 55def ensure_list(value: t.Collection[T]) -> t.List[T]:
 56    ...
 57
 58
 59@t.overload
 60def ensure_list(value: T) -> t.List[T]:
 61    ...
 62
 63
 64def ensure_list(value):
 65    """
 66    Ensures that a value is a list, otherwise casts or wraps it into one.
 67
 68    Args:
 69        value: The value of interest.
 70
 71    Returns:
 72        The value cast as a list if it's a list or a tuple, or else the value wrapped in a list.
 73    """
 74    if value is None:
 75        return []
 76    if isinstance(value, (list, tuple)):
 77        return list(value)
 78
 79    return [value]
 80
 81
 82@t.overload
 83def ensure_collection(value: t.Collection[T]) -> t.Collection[T]:
 84    ...
 85
 86
 87@t.overload
 88def ensure_collection(value: T) -> t.Collection[T]:
 89    ...
 90
 91
 92def ensure_collection(value):
 93    """
 94    Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.
 95
 96    Args:
 97        value: The value of interest.
 98
 99    Returns:
100        The value if it's a collection, or else the value wrapped in a list.
101    """
102    if value is None:
103        return []
104    return (
105        value if isinstance(value, Collection) and not isinstance(value, (str, bytes)) else [value]
106    )
107
108
109def csv(*args: str, sep: str = ", ") -> str:
110    """
111    Formats any number of string arguments as CSV.
112
113    Args:
114        args: The string arguments to format.
115        sep: The argument separator.
116
117    Returns:
118        The arguments formatted as a CSV string.
119    """
120    return sep.join(arg for arg in args if arg)
121
122
123def subclasses(
124    module_name: str,
125    classes: t.Type | t.Tuple[t.Type, ...],
126    exclude: t.Type | t.Tuple[t.Type, ...] = (),
127) -> t.List[t.Type]:
128    """
129    Returns all subclasses for a collection of classes, possibly excluding some of them.
130
131    Args:
132        module_name: The name of the module to search for subclasses in.
133        classes: Class(es) we want to find the subclasses of.
134        exclude: Class(es) we want to exclude from the returned list.
135
136    Returns:
137        The target subclasses.
138    """
139    return [
140        obj
141        for _, obj in inspect.getmembers(
142            sys.modules[module_name],
143            lambda obj: inspect.isclass(obj) and issubclass(obj, classes) and obj not in exclude,
144        )
145    ]
146
147
148def apply_index_offset(
149    this: exp.Expression,
150    expressions: t.List[E],
151    offset: int,
152) -> t.List[E]:
153    """
154    Applies an offset to a given integer literal expression.
155
156    Args:
157        this: The target of the index.
158        expressions: The expression the offset will be applied to, wrapped in a list.
159        offset: The offset that will be applied.
160
161    Returns:
162        The original expression with the offset applied to it, wrapped in a list. If the provided
163        `expressions` argument contains more than one expression, it's returned unaffected.
164    """
165    if not offset or len(expressions) != 1:
166        return expressions
167
168    expression = expressions[0]
169
170    from sqlglot import exp
171    from sqlglot.optimizer.annotate_types import annotate_types
172    from sqlglot.optimizer.simplify import simplify
173
174    if not this.type:
175        annotate_types(this)
176
177    if t.cast(exp.DataType, this.type).this not in (
178        exp.DataType.Type.UNKNOWN,
179        exp.DataType.Type.ARRAY,
180    ):
181        return expressions
182
183    if not expression.type:
184        annotate_types(expression)
185    if t.cast(exp.DataType, expression.type).this in exp.DataType.INTEGER_TYPES:
186        logger.warning("Applying array index offset (%s)", offset)
187        expression = simplify(
188            exp.Add(this=expression.copy(), expression=exp.Literal.number(offset))
189        )
190        return [expression]
191
192    return expressions
193
194
195def camel_to_snake_case(name: str) -> str:
196    """Converts `name` from camelCase to snake_case and returns the result."""
197    return CAMEL_CASE_PATTERN.sub("_", name).upper()
198
199
200def while_changing(expression: Expression, func: t.Callable[[Expression], E]) -> E:
201    """
202    Applies a transformation to a given expression until a fix point is reached.
203
204    Args:
205        expression: The expression to be transformed.
206        func: The transformation to be applied.
207
208    Returns:
209        The transformed expression.
210    """
211    while True:
212        for n, *_ in reversed(tuple(expression.walk())):
213            n._hash = hash(n)
214
215        start = hash(expression)
216        expression = func(expression)
217
218        for n, *_ in expression.walk():
219            n._hash = None
220        if start == hash(expression):
221            break
222
223    return expression
224
225
226def tsort(dag: t.Dict[T, t.Set[T]]) -> t.List[T]:
227    """
228    Sorts a given directed acyclic graph in topological order.
229
230    Args:
231        dag: The graph to be sorted.
232
233    Returns:
234        A list that contains all of the graph's nodes in topological order.
235    """
236    result = []
237
238    for node, deps in tuple(dag.items()):
239        for dep in deps:
240            if not dep in dag:
241                dag[dep] = set()
242
243    while dag:
244        current = {node for node, deps in dag.items() if not deps}
245
246        if not current:
247            raise ValueError("Cycle error")
248
249        for node in current:
250            dag.pop(node)
251
252        for deps in dag.values():
253            deps -= current
254
255        result.extend(sorted(current))  # type: ignore
256
257    return result
258
259
260def open_file(file_name: str) -> t.TextIO:
261    """Open a file that may be compressed as gzip and return it in universal newline mode."""
262    with open(file_name, "rb") as f:
263        gzipped = f.read(2) == b"\x1f\x8b"
264
265    if gzipped:
266        import gzip
267
268        return gzip.open(file_name, "rt", newline="")
269
270    return open(file_name, encoding="utf-8", newline="")
271
272
273@contextmanager
274def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
275    """
276    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
277
278    Args:
279        read_csv: A `ReadCSV` function call.
280
281    Yields:
282        A python csv reader.
283    """
284    args = read_csv.expressions
285    file = open_file(read_csv.name)
286
287    delimiter = ","
288    args = iter(arg.name for arg in args)
289    for k, v in zip(args, args):
290        if k == "delimiter":
291            delimiter = v
292
293    try:
294        import csv as csv_
295
296        yield csv_.reader(file, delimiter=delimiter)
297    finally:
298        file.close()
299
300
301def find_new_name(taken: t.Collection[str], base: str) -> str:
302    """
303    Searches for a new name.
304
305    Args:
306        taken: A collection of taken names.
307        base: Base name to alter.
308
309    Returns:
310        The new, available name.
311    """
312    if base not in taken:
313        return base
314
315    i = 2
316    new = f"{base}_{i}"
317    while new in taken:
318        i += 1
319        new = f"{base}_{i}"
320
321    return new
322
323
324def name_sequence(prefix: str) -> t.Callable[[], str]:
325    """Returns a name generator given a prefix (e.g. a0, a1, a2, ... if the prefix is "a")."""
326    sequence = count()
327    return lambda: f"{prefix}{next(sequence)}"
328
329
330def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
331    """Returns a dictionary created from an object's attributes."""
332    return {
333        **{k: v.copy() if hasattr(v, "copy") else copy(v) for k, v in vars(obj).items()},
334        **kwargs,
335    }
336
337
338def split_num_words(
339    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
340) -> t.List[t.Optional[str]]:
341    """
342    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
343
344    Args:
345        value: The value to be split.
346        sep: The value to use to split on.
347        min_num_words: The minimum number of words that are going to be in the result.
348        fill_from_start: Indicates that if `None` values should be inserted at the start or end of the list.
349
350    Examples:
351        >>> split_num_words("db.table", ".", 3)
352        [None, 'db', 'table']
353        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
354        ['db', 'table', None]
355        >>> split_num_words("db.table", ".", 1)
356        ['db', 'table']
357
358    Returns:
359        The list of words returned by `split`, possibly augmented by a number of `None` values.
360    """
361    words = value.split(sep)
362    if fill_from_start:
363        return [None] * (min_num_words - len(words)) + words
364    return words + [None] * (min_num_words - len(words))
365
366
367def is_iterable(value: t.Any) -> bool:
368    """
369    Checks if the value is an iterable, excluding the types `str` and `bytes`.
370
371    Examples:
372        >>> is_iterable([1,2])
373        True
374        >>> is_iterable("test")
375        False
376
377    Args:
378        value: The value to check if it is an iterable.
379
380    Returns:
381        A `bool` value indicating if it is an iterable.
382    """
383    from sqlglot import Expression
384
385    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes, Expression))
386
387
388def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
389    """
390    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
391    type `str` and `bytes` are not regarded as iterables.
392
393    Examples:
394        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
395        [1, 2, 3, 4, 5, 'bla']
396        >>> list(flatten([1, 2, 3]))
397        [1, 2, 3]
398
399    Args:
400        values: The value to be flattened.
401
402    Yields:
403        Non-iterable elements in `values`.
404    """
405    for value in values:
406        if is_iterable(value):
407            yield from flatten(value)
408        else:
409            yield value
410
411
412def dict_depth(d: t.Dict) -> int:
413    """
414    Get the nesting depth of a dictionary.
415
416    Example:
417        >>> dict_depth(None)
418        0
419        >>> dict_depth({})
420        1
421        >>> dict_depth({"a": "b"})
422        1
423        >>> dict_depth({"a": {}})
424        2
425        >>> dict_depth({"a": {"b": {}}})
426        3
427    """
428    try:
429        return 1 + dict_depth(next(iter(d.values())))
430    except AttributeError:
431        # d doesn't have attribute "values"
432        return 0
433    except StopIteration:
434        # d.values() returns an empty sequence
435        return 1
436
437
438def first(it: t.Iterable[T]) -> T:
439    """Returns the first element from an iterable (useful for sets)."""
440    return next(i for i in it)
441
442
443def merge_ranges(ranges: t.List[t.Tuple[A, A]]) -> t.List[t.Tuple[A, A]]:
444    if not ranges:
445        return []
446
447    ranges = sorted(ranges)
448
449    merged = [ranges[0]]
450
451    for start, end in ranges[1:]:
452        last_start, last_end = merged[-1]
453
454        if start <= last_end:
455            merged[-1] = (last_start, max(last_end, end))
456        else:
457            merged.append((start, end))
458
459    return merged