Edit on GitHub

# sqlglot.helper

View Source

      1from __future__ import annotations
      2
      3import datetime
      4import inspect
      5import logging
      6import re
      7import sys
      8import typing as t
      9from collections.abc import Collection, Set
     10from contextlib import contextmanager
     11from copy import copy
     12from enum import Enum
     13from itertools import count
     14
     15if t.TYPE_CHECKING:
     16    from sqlglot import exp
     17    from sqlglot._typing import A, E, T
     18    from sqlglot.expressions import Expression
     19
     20
     21CAMEL_CASE_PATTERN = re.compile("(?<!^)(?=[A-Z])")
     22PYTHON_VERSION = sys.version_info[:2]
     23logger = logging.getLogger("sqlglot")
     24
     25
     26class AutoName(Enum):
     27    """
     28    This is used for creating Enum classes where `auto()` is the string form
     29    of the corresponding enum's identifier (e.g. FOO.value results in "FOO").
     30
     31    Reference: https://docs.python.org/3/howto/enum.html#using-automatic-values
     32    """
     33
     34    def _generate_next_value_(name, _start, _count, _last_values):
     35        return name
     36
     37
     38class classproperty(property):
     39    """
     40    Similar to a normal property but works for class methods
     41    """
     42
     43    def __get__(self, obj: t.Any, owner: t.Any = None) -> t.Any:
     44        return classmethod(self.fget).__get__(None, owner)()  # type: ignore
     45
     46
     47def seq_get(seq: t.Sequence[T], index: int) -> t.Optional[T]:
     48    """Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds."""
     49    try:
     50        return seq[index]
     51    except IndexError:
     52        return None
     53
     54
     55@t.overload
     56def ensure_list(value: t.Collection[T]) -> t.List[T]: ...
     57
     58
     59@t.overload
     60def ensure_list(value: T) -> t.List[T]: ...
     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@t.overload
     86def ensure_collection(value: T) -> t.Collection[T]: ...
     87
     88
     89def ensure_collection(value):
     90    """
     91    Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.
     92
     93    Args:
     94        value: The value of interest.
     95
     96    Returns:
     97        The value if it's a collection, or else the value wrapped in a list.
     98    """
     99    if value is None:
    100        return []
    101    return (
    102        value if isinstance(value, Collection) and not isinstance(value, (str, bytes)) else [value]
    103    )
    104
    105
    106def csv(*args: str, sep: str = ", ") -> str:
    107    """
    108    Formats any number of string arguments as CSV.
    109
    110    Args:
    111        args: The string arguments to format.
    112        sep: The argument separator.
    113
    114    Returns:
    115        The arguments formatted as a CSV string.
    116    """
    117    return sep.join(arg for arg in args if arg)
    118
    119
    120def subclasses(
    121    module_name: str,
    122    classes: t.Type | t.Tuple[t.Type, ...],
    123    exclude: t.Type | t.Tuple[t.Type, ...] = (),
    124) -> t.List[t.Type]:
    125    """
    126    Returns all subclasses for a collection of classes, possibly excluding some of them.
    127
    128    Args:
    129        module_name: The name of the module to search for subclasses in.
    130        classes: Class(es) we want to find the subclasses of.
    131        exclude: Class(es) we want to exclude from the returned list.
    132
    133    Returns:
    134        The target subclasses.
    135    """
    136    return [
    137        obj
    138        for _, obj in inspect.getmembers(
    139            sys.modules[module_name],
    140            lambda obj: inspect.isclass(obj) and issubclass(obj, classes) and obj not in exclude,
    141        )
    142    ]
    143
    144
    145def apply_index_offset(
    146    this: exp.Expression,
    147    expressions: t.List[E],
    148    offset: int,
    149) -> t.List[E]:
    150    """
    151    Applies an offset to a given integer literal expression.
    152
    153    Args:
    154        this: The target of the index.
    155        expressions: The expression the offset will be applied to, wrapped in a list.
    156        offset: The offset that will be applied.
    157
    158    Returns:
    159        The original expression with the offset applied to it, wrapped in a list. If the provided
    160        `expressions` argument contains more than one expression, it's returned unaffected.
    161    """
    162    if not offset or len(expressions) != 1:
    163        return expressions
    164
    165    expression = expressions[0]
    166
    167    from sqlglot import exp
    168    from sqlglot.optimizer.annotate_types import annotate_types
    169    from sqlglot.optimizer.simplify import simplify
    170
    171    if not this.type:
    172        annotate_types(this)
    173
    174    if t.cast(exp.DataType, this.type).this not in (
    175        exp.DataType.Type.UNKNOWN,
    176        exp.DataType.Type.ARRAY,
    177    ):
    178        return expressions
    179
    180    if not expression.type:
    181        annotate_types(expression)
    182
    183    if t.cast(exp.DataType, expression.type).this in exp.DataType.INTEGER_TYPES:
    184        logger.info("Applying array index offset (%s)", offset)
    185        expression = simplify(expression + offset)
    186        return [expression]
    187
    188    return expressions
    189
    190
    191def camel_to_snake_case(name: str) -> str:
    192    """Converts `name` from camelCase to snake_case and returns the result."""
    193    return CAMEL_CASE_PATTERN.sub("_", name).upper()
    194
    195
    196def while_changing(expression: Expression, func: t.Callable[[Expression], E]) -> E:
    197    """
    198    Applies a transformation to a given expression until a fix point is reached.
    199
    200    Args:
    201        expression: The expression to be transformed.
    202        func: The transformation to be applied.
    203
    204    Returns:
    205        The transformed expression.
    206    """
    207    while True:
    208        for n in reversed(tuple(expression.walk())):
    209            n._hash = hash(n)
    210
    211        start = hash(expression)
    212        expression = func(expression)
    213
    214        for n in expression.walk():
    215            n._hash = None
    216        if start == hash(expression):
    217            break
    218
    219    return expression
    220
    221
    222def tsort(dag: t.Dict[T, t.Set[T]]) -> t.List[T]:
    223    """
    224    Sorts a given directed acyclic graph in topological order.
    225
    226    Args:
    227        dag: The graph to be sorted.
    228
    229    Returns:
    230        A list that contains all of the graph's nodes in topological order.
    231    """
    232    result = []
    233
    234    for node, deps in tuple(dag.items()):
    235        for dep in deps:
    236            if dep not in dag:
    237                dag[dep] = set()
    238
    239    while dag:
    240        current = {node for node, deps in dag.items() if not deps}
    241
    242        if not current:
    243            raise ValueError("Cycle error")
    244
    245        for node in current:
    246            dag.pop(node)
    247
    248        for deps in dag.values():
    249            deps -= current
    250
    251        result.extend(sorted(current))  # type: ignore
    252
    253    return result
    254
    255
    256def open_file(file_name: str) -> t.TextIO:
    257    """Open a file that may be compressed as gzip and return it in universal newline mode."""
    258    with open(file_name, "rb") as f:
    259        gzipped = f.read(2) == b"\x1f\x8b"
    260
    261    if gzipped:
    262        import gzip
    263
    264        return gzip.open(file_name, "rt", newline="")
    265
    266    return open(file_name, encoding="utf-8", newline="")
    267
    268
    269@contextmanager
    270def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
    271    """
    272    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
    273
    274    Args:
    275        read_csv: A `ReadCSV` function call.
    276
    277    Yields:
    278        A python csv reader.
    279    """
    280    args = read_csv.expressions
    281    file = open_file(read_csv.name)
    282
    283    delimiter = ","
    284    args = iter(arg.name for arg in args)  # type: ignore
    285    for k, v in zip(args, args):
    286        if k == "delimiter":
    287            delimiter = v
    288
    289    try:
    290        import csv as csv_
    291
    292        yield csv_.reader(file, delimiter=delimiter)
    293    finally:
    294        file.close()
    295
    296
    297def find_new_name(taken: t.Collection[str], base: str) -> str:
    298    """
    299    Searches for a new name.
    300
    301    Args:
    302        taken: A collection of taken names.
    303        base: Base name to alter.
    304
    305    Returns:
    306        The new, available name.
    307    """
    308    if base not in taken:
    309        return base
    310
    311    i = 2
    312    new = f"{base}_{i}"
    313    while new in taken:
    314        i += 1
    315        new = f"{base}_{i}"
    316
    317    return new
    318
    319
    320def is_int(text: str) -> bool:
    321    return is_type(text, int)
    322
    323
    324def is_float(text: str) -> bool:
    325    return is_type(text, float)
    326
    327
    328def is_type(text: str, target_type: t.Type) -> bool:
    329    try:
    330        target_type(text)
    331        return True
    332    except ValueError:
    333        return False
    334
    335
    336def name_sequence(prefix: str) -> t.Callable[[], str]:
    337    """Returns a name generator given a prefix (e.g. a0, a1, a2, ... if the prefix is "a")."""
    338    sequence = count()
    339    return lambda: f"{prefix}{next(sequence)}"
    340
    341
    342def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
    343    """Returns a dictionary created from an object's attributes."""
    344    return {
    345        **{k: v.copy() if hasattr(v, "copy") else copy(v) for k, v in vars(obj).items()},
    346        **kwargs,
    347    }
    348
    349
    350def split_num_words(
    351    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
    352) -> t.List[t.Optional[str]]:
    353    """
    354    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
    355
    356    Args:
    357        value: The value to be split.
    358        sep: The value to use to split on.
    359        min_num_words: The minimum number of words that are going to be in the result.
    360        fill_from_start: Indicates that if `None` values should be inserted at the start or end of the list.
    361
    362    Examples:
    363        >>> split_num_words("db.table", ".", 3)
    364        [None, 'db', 'table']
    365        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
    366        ['db', 'table', None]
    367        >>> split_num_words("db.table", ".", 1)
    368        ['db', 'table']
    369
    370    Returns:
    371        The list of words returned by `split`, possibly augmented by a number of `None` values.
    372    """
    373    words = value.split(sep)
    374    if fill_from_start:
    375        return [None] * (min_num_words - len(words)) + words
    376    return words + [None] * (min_num_words - len(words))
    377
    378
    379def is_iterable(value: t.Any) -> bool:
    380    """
    381    Checks if the value is an iterable, excluding the types `str` and `bytes`.
    382
    383    Examples:
    384        >>> is_iterable([1,2])
    385        True
    386        >>> is_iterable("test")
    387        False
    388
    389    Args:
    390        value: The value to check if it is an iterable.
    391
    392    Returns:
    393        A `bool` value indicating if it is an iterable.
    394    """
    395    from sqlglot import Expression
    396
    397    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes, Expression))
    398
    399
    400def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
    401    """
    402    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
    403    type `str` and `bytes` are not regarded as iterables.
    404
    405    Examples:
    406        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
    407        [1, 2, 3, 4, 5, 'bla']
    408        >>> list(flatten([1, 2, 3]))
    409        [1, 2, 3]
    410
    411    Args:
    412        values: The value to be flattened.
    413
    414    Yields:
    415        Non-iterable elements in `values`.
    416    """
    417    for value in values:
    418        if is_iterable(value):
    419            yield from flatten(value)
    420        else:
    421            yield value
    422
    423
    424def dict_depth(d: t.Dict) -> int:
    425    """
    426    Get the nesting depth of a dictionary.
    427
    428    Example:
    429        >>> dict_depth(None)
    430        0
    431        >>> dict_depth({})
    432        1
    433        >>> dict_depth({"a": "b"})
    434        1
    435        >>> dict_depth({"a": {}})
    436        2
    437        >>> dict_depth({"a": {"b": {}}})
    438        3
    439    """
    440    try:
    441        return 1 + dict_depth(next(iter(d.values())))
    442    except AttributeError:
    443        # d doesn't have attribute "values"
    444        return 0
    445    except StopIteration:
    446        # d.values() returns an empty sequence
    447        return 1
    448
    449
    450def first(it: t.Iterable[T]) -> T:
    451    """Returns the first element from an iterable (useful for sets)."""
    452    return next(i for i in it)
    453
    454
    455def merge_ranges(ranges: t.List[t.Tuple[A, A]]) -> t.List[t.Tuple[A, A]]:
    456    """
    457    Merges a sequence of ranges, represented as tuples (low, high) whose values
    458    belong to some totally-ordered set.
    459
    460    Example:
    461        >>> merge_ranges([(1, 3), (2, 6)])
    462        [(1, 6)]
    463    """
    464    if not ranges:
    465        return []
    466
    467    ranges = sorted(ranges)
    468
    469    merged = [ranges[0]]
    470
    471    for start, end in ranges[1:]:
    472        last_start, last_end = merged[-1]
    473
    474        if start <= last_end:
    475            merged[-1] = (last_start, max(last_end, end))
    476        else:
    477            merged.append((start, end))
    478
    479    return merged
    480
    481
    482def is_iso_date(text: str) -> bool:
    483    try:
    484        datetime.date.fromisoformat(text)
    485        return True
    486    except ValueError:
    487        return False
    488
    489
    490def is_iso_datetime(text: str) -> bool:
    491    try:
    492        datetime.datetime.fromisoformat(text)
    493        return True
    494    except ValueError:
    495        return False
    496
    497
    498# Interval units that operate on date components
    499DATE_UNITS = {"day", "week", "month", "quarter", "year", "year_month"}
    500
    501
    502def is_date_unit(expression: t.Optional[exp.Expression]) -> bool:
    503    return expression is not None and expression.name.lower() in DATE_UNITS
    504
    505
    506K = t.TypeVar("K")
    507V = t.TypeVar("V")
    508
    509
    510class SingleValuedMapping(t.Mapping[K, V]):
    511    """
    512    Mapping where all keys return the same value.
    513
    514    This rigamarole is meant to avoid copying keys, which was originally intended
    515    as an optimization while qualifying columns for tables with lots of columns.
    516    """
    517
    518    def __init__(self, keys: t.Collection[K], value: V):
    519        self._keys = keys if isinstance(keys, Set) else set(keys)
    520        self._value = value
    521
    522    def __getitem__(self, key: K) -> V:
    523        if key in self._keys:
    524            return self._value
    525        raise KeyError(key)
    526
    527    def __len__(self) -> int:
    528        return len(self._keys)
    529
    530    def __iter__(self) -> t.Iterator[K]:
    531        return iter(self._keys)

CAMEL_CASE_PATTERN = re.compile('(?<!^)(?=[A-Z])')
PYTHON_VERSION = (3, 10)
logger = <Logger sqlglot (WARNING)>
class AutoName(enum.Enum): View Source

    27class AutoName(Enum):
    28    """
    29    This is used for creating Enum classes where `auto()` is the string form
    30    of the corresponding enum's identifier (e.g. FOO.value results in "FOO").
    31
    32    Reference: https://docs.python.org/3/howto/enum.html#using-automatic-values
    33    """
    34
    35    def _generate_next_value_(name, _start, _count, _last_values):
    36        return name

This is used for creating Enum classes where `auto()` is the string form of the corresponding enum's identifier (e.g. FOO.value results in "FOO").

Reference: https://docs.python.org/3/howto/enum.html#using-automatic-values

##### Inherited Members

enum.Enum
  name
  value

class classproperty(builtins.property): View Source

    39class classproperty(property):
    40    """
    41    Similar to a normal property but works for class methods
    42    """
    43
    44    def __get__(self, obj: t.Any, owner: t.Any = None) -> t.Any:
    45        return classmethod(self.fget).__get__(None, owner)()  # type: ignore

Similar to a normal property but works for class methods

##### Inherited Members

builtins.property
  property
  getter
  setter
  deleter
  fget
  fset
  fdel

def seq_get(seq: Sequence[~T], index: int) -> Optional[~T]: View Source

    48def seq_get(seq: t.Sequence[T], index: int) -> t.Optional[T]:
    49    """Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds."""
    50    try:
    51        return seq[index]
    52    except IndexError:
    53        return None

Returns the value in `seq` at position `index`, or `None` if `index` is out of bounds.

def ensure_list(value): View Source

    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]

Ensures that a value is a list, otherwise casts or wraps it into one.

###### Arguments:

- value: The value of interest.

###### Returns:

> The value cast as a list if it's a list or a tuple, or else the value wrapped in a list.

def ensure_collection(value): View Source

     90def ensure_collection(value):
     91    """
     92    Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.
     93
     94    Args:
     95        value: The value of interest.
     96
     97    Returns:
     98        The value if it's a collection, or else the value wrapped in a list.
     99    """
    100    if value is None:
    101        return []
    102    return (
    103        value if isinstance(value, Collection) and not isinstance(value, (str, bytes)) else [value]
    104    )

Ensures that a value is a collection (excluding `str` and `bytes`), otherwise wraps it into a list.

###### Arguments:

- value: The value of interest.

###### Returns:

> The value if it's a collection, or else the value wrapped in a list.

def csv(*args: str, sep: str = ', ') -> str: View Source

    107def csv(*args: str, sep: str = ", ") -> str:
    108    """
    109    Formats any number of string arguments as CSV.
    110
    111    Args:
    112        args: The string arguments to format.
    113        sep: The argument separator.
    114
    115    Returns:
    116        The arguments formatted as a CSV string.
    117    """
    118    return sep.join(arg for arg in args if arg)

Formats any number of string arguments as CSV.

###### Arguments:

- args: The string arguments to format.
- sep: The argument separator.

###### Returns:

> The arguments formatted as a CSV string.

def subclasses( module_name: str, classes: Union[Type, Tuple[Type, ...]], exclude: Union[Type, Tuple[Type, ...]] = ()) -> List[Type]: View Source

    121def subclasses(
    122    module_name: str,
    123    classes: t.Type | t.Tuple[t.Type, ...],
    124    exclude: t.Type | t.Tuple[t.Type, ...] = (),
    125) -> t.List[t.Type]:
    126    """
    127    Returns all subclasses for a collection of classes, possibly excluding some of them.
    128
    129    Args:
    130        module_name: The name of the module to search for subclasses in.
    131        classes: Class(es) we want to find the subclasses of.
    132        exclude: Class(es) we want to exclude from the returned list.
    133
    134    Returns:
    135        The target subclasses.
    136    """
    137    return [
    138        obj
    139        for _, obj in inspect.getmembers(
    140            sys.modules[module_name],
    141            lambda obj: inspect.isclass(obj) and issubclass(obj, classes) and obj not in exclude,
    142        )
    143    ]

Returns all subclasses for a collection of classes, possibly excluding some of them.

###### Arguments:

- module_name: The name of the module to search for subclasses in.
- classes: Class(es) we want to find the subclasses of.
- exclude: Class(es) we want to exclude from the returned list.

###### Returns:

> The target subclasses.

def apply_index_offset( this: sqlglot.expressions.Expression, expressions: List[~E], offset: int) -> List[~E]: View Source

    146def apply_index_offset(
    147    this: exp.Expression,
    148    expressions: t.List[E],
    149    offset: int,
    150) -> t.List[E]:
    151    """
    152    Applies an offset to a given integer literal expression.
    153
    154    Args:
    155        this: The target of the index.
    156        expressions: The expression the offset will be applied to, wrapped in a list.
    157        offset: The offset that will be applied.
    158
    159    Returns:
    160        The original expression with the offset applied to it, wrapped in a list. If the provided
    161        `expressions` argument contains more than one expression, it's returned unaffected.
    162    """
    163    if not offset or len(expressions) != 1:
    164        return expressions
    165
    166    expression = expressions[0]
    167
    168    from sqlglot import exp
    169    from sqlglot.optimizer.annotate_types import annotate_types
    170    from sqlglot.optimizer.simplify import simplify
    171
    172    if not this.type:
    173        annotate_types(this)
    174
    175    if t.cast(exp.DataType, this.type).this not in (
    176        exp.DataType.Type.UNKNOWN,
    177        exp.DataType.Type.ARRAY,
    178    ):
    179        return expressions
    180
    181    if not expression.type:
    182        annotate_types(expression)
    183
    184    if t.cast(exp.DataType, expression.type).this in exp.DataType.INTEGER_TYPES:
    185        logger.info("Applying array index offset (%s)", offset)
    186        expression = simplify(expression + offset)
    187        return [expression]
    188
    189    return expressions

Applies an offset to a given integer literal expression.

###### Arguments:

- this: The target of the index.
- expressions: The expression the offset will be applied to, wrapped in a list.
- offset: The offset that will be applied.

###### Returns:

> The original expression with the offset applied to it, wrapped in a list. If the provided `expressions` argument contains more than one expression, it's returned unaffected.

def camel_to_snake_case(name: str) -> str: View Source

    192def camel_to_snake_case(name: str) -> str:
    193    """Converts `name` from camelCase to snake_case and returns the result."""
    194    return CAMEL_CASE_PATTERN.sub("_", name).upper()

Converts `name` from camelCase to snake_case and returns the result.

def while_changing( expression: sqlglot.expressions.Expression, func: Callable[[sqlglot.expressions.Expression], ~E]) -> ~E: View Source

    197def while_changing(expression: Expression, func: t.Callable[[Expression], E]) -> E:
    198    """
    199    Applies a transformation to a given expression until a fix point is reached.
    200
    201    Args:
    202        expression: The expression to be transformed.
    203        func: The transformation to be applied.
    204
    205    Returns:
    206        The transformed expression.
    207    """
    208    while True:
    209        for n in reversed(tuple(expression.walk())):
    210            n._hash = hash(n)
    211
    212        start = hash(expression)
    213        expression = func(expression)
    214
    215        for n in expression.walk():
    216            n._hash = None
    217        if start == hash(expression):
    218            break
    219
    220    return expression

Applies a transformation to a given expression until a fix point is reached.

###### Arguments:

- expression: The expression to be transformed.
- func: The transformation to be applied.

###### Returns:

> The transformed expression.

def tsort(dag: Dict[~T, Set[~T]]) -> List[~T]: View Source

    223def tsort(dag: t.Dict[T, t.Set[T]]) -> t.List[T]:
    224    """
    225    Sorts a given directed acyclic graph in topological order.
    226
    227    Args:
    228        dag: The graph to be sorted.
    229
    230    Returns:
    231        A list that contains all of the graph's nodes in topological order.
    232    """
    233    result = []
    234
    235    for node, deps in tuple(dag.items()):
    236        for dep in deps:
    237            if dep not in dag:
    238                dag[dep] = set()
    239
    240    while dag:
    241        current = {node for node, deps in dag.items() if not deps}
    242
    243        if not current:
    244            raise ValueError("Cycle error")
    245
    246        for node in current:
    247            dag.pop(node)
    248
    249        for deps in dag.values():
    250            deps -= current
    251
    252        result.extend(sorted(current))  # type: ignore
    253
    254    return result

Sorts a given directed acyclic graph in topological order.

###### Arguments:

- dag: The graph to be sorted.

###### Returns:

> A list that contains all of the graph's nodes in topological order.

def open_file(file_name: str) -> <class 'TextIO'>: View Source

    257def open_file(file_name: str) -> t.TextIO:
    258    """Open a file that may be compressed as gzip and return it in universal newline mode."""
    259    with open(file_name, "rb") as f:
    260        gzipped = f.read(2) == b"\x1f\x8b"
    261
    262    if gzipped:
    263        import gzip
    264
    265        return gzip.open(file_name, "rt", newline="")
    266
    267    return open(file_name, encoding="utf-8", newline="")

Open a file that may be compressed as gzip and return it in universal newline mode.

@contextmanager
def csv_reader(read_csv: sqlglot.expressions.ReadCSV) -> Any: View Source

    270@contextmanager
    271def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
    272    """
    273    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
    274
    275    Args:
    276        read_csv: A `ReadCSV` function call.
    277
    278    Yields:
    279        A python csv reader.
    280    """
    281    args = read_csv.expressions
    282    file = open_file(read_csv.name)
    283
    284    delimiter = ","
    285    args = iter(arg.name for arg in args)  # type: ignore
    286    for k, v in zip(args, args):
    287        if k == "delimiter":
    288            delimiter = v
    289
    290    try:
    291        import csv as csv_
    292
    293        yield csv_.reader(file, delimiter=delimiter)
    294    finally:
    295        file.close()

Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.

###### Arguments:

- read_csv: A `ReadCSV` function call.

###### Yields:

> A python csv reader.

def find_new_name(taken: Collection[str], base: str) -> str: View Source

    298def find_new_name(taken: t.Collection[str], base: str) -> str:
    299    """
    300    Searches for a new name.
    301
    302    Args:
    303        taken: A collection of taken names.
    304        base: Base name to alter.
    305
    306    Returns:
    307        The new, available name.
    308    """
    309    if base not in taken:
    310        return base
    311
    312    i = 2
    313    new = f"{base}_{i}"
    314    while new in taken:
    315        i += 1
    316        new = f"{base}_{i}"
    317
    318    return new

Searches for a new name.

###### Arguments:

- taken: A collection of taken names.
- base: Base name to alter.

###### Returns:

> The new, available name.

def is_int(text: str) -> bool: View Source

    321def is_int(text: str) -> bool:
    322    return is_type(text, int)

def is_float(text: str) -> bool: View Source

    325def is_float(text: str) -> bool:
    326    return is_type(text, float)

def is_type(text: str, target_type: Type) -> bool: View Source

    329def is_type(text: str, target_type: t.Type) -> bool:
    330    try:
    331        target_type(text)
    332        return True
    333    except ValueError:
    334        return False

def name_sequence(prefix: str) -> Callable[[], str]: View Source

    337def name_sequence(prefix: str) -> t.Callable[[], str]:
    338    """Returns a name generator given a prefix (e.g. a0, a1, a2, ... if the prefix is "a")."""
    339    sequence = count()
    340    return lambda: f"{prefix}{next(sequence)}"

Returns a name generator given a prefix (e.g. a0, a1, a2, ... if the prefix is "a").

def object_to_dict(obj: Any, **kwargs) -> Dict: View Source

    343def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
    344    """Returns a dictionary created from an object's attributes."""
    345    return {
    346        **{k: v.copy() if hasattr(v, "copy") else copy(v) for k, v in vars(obj).items()},
    347        **kwargs,
    348    }

Returns a dictionary created from an object's attributes.

def split_num_words( value: str, sep: str, min_num_words: int, fill_from_start: bool = True) -> List[Optional[str]]: View Source

    351def split_num_words(
    352    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
    353) -> t.List[t.Optional[str]]:
    354    """
    355    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
    356
    357    Args:
    358        value: The value to be split.
    359        sep: The value to use to split on.
    360        min_num_words: The minimum number of words that are going to be in the result.
    361        fill_from_start: Indicates that if `None` values should be inserted at the start or end of the list.
    362
    363    Examples:
    364        >>> split_num_words("db.table", ".", 3)
    365        [None, 'db', 'table']
    366        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
    367        ['db', 'table', None]
    368        >>> split_num_words("db.table", ".", 1)
    369        ['db', 'table']
    370
    371    Returns:
    372        The list of words returned by `split`, possibly augmented by a number of `None` values.
    373    """
    374    words = value.split(sep)
    375    if fill_from_start:
    376        return [None] * (min_num_words - len(words)) + words
    377    return words + [None] * (min_num_words - len(words))

Perform a split on a value and return N words as a result with `None` used for words that don't exist.

###### Arguments:

- value: The value to be split.
- sep: The value to use to split on.
- min_num_words: The minimum number of words that are going to be in the result.
- fill_from_start: Indicates that if `None` values should be inserted at the start or end of the list.

###### Examples:

>     >>> split_num_words("db.table", ".", 3)
>     [None, 'db', 'table']
>     >>> split_num_words("db.table", ".", 3, fill_from_start=False)
>     ['db', 'table', None]
>     >>> split_num_words("db.table", ".", 1)
>     ['db', 'table']

###### Returns:

> The list of words returned by `split`, possibly augmented by a number of `None` values.

def is_iterable(value: Any) -> bool: View Source

    380def is_iterable(value: t.Any) -> bool:
    381    """
    382    Checks if the value is an iterable, excluding the types `str` and `bytes`.
    383
    384    Examples:
    385        >>> is_iterable([1,2])
    386        True
    387        >>> is_iterable("test")
    388        False
    389
    390    Args:
    391        value: The value to check if it is an iterable.
    392
    393    Returns:
    394        A `bool` value indicating if it is an iterable.
    395    """
    396    from sqlglot import Expression
    397
    398    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes, Expression))

Checks if the value is an iterable, excluding the types `str` and `bytes`.

###### Examples:

>     >>> is_iterable([1,2])
>     True
>     >>> is_iterable("test")
>     False

###### Arguments:

- value: The value to check if it is an iterable.

###### Returns:

> A `bool` value indicating if it is an iterable.

def flatten(values: Iterable[Union[Iterable[Any], Any]]) -> Iterator[Any]: View Source

    401def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
    402    """
    403    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
    404    type `str` and `bytes` are not regarded as iterables.
    405
    406    Examples:
    407        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
    408        [1, 2, 3, 4, 5, 'bla']
    409        >>> list(flatten([1, 2, 3]))
    410        [1, 2, 3]
    411
    412    Args:
    413        values: The value to be flattened.
    414
    415    Yields:
    416        Non-iterable elements in `values`.
    417    """
    418    for value in values:
    419        if is_iterable(value):
    420            yield from flatten(value)
    421        else:
    422            yield value

Flattens an iterable that can contain both iterable and non-iterable elements. Objects of type `str` and `bytes` are not regarded as iterables.

###### Examples:

>     >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
>     [1, 2, 3, 4, 5, 'bla']
>     >>> list(flatten([1, 2, 3]))
>     [1, 2, 3]

###### Arguments:

- values: The value to be flattened.

###### Yields:

> Non-iterable elements in `values`.

def dict_depth(d: Dict) -> int: View Source

    425def dict_depth(d: t.Dict) -> int:
    426    """
    427    Get the nesting depth of a dictionary.
    428
    429    Example:
    430        >>> dict_depth(None)
    431        0
    432        >>> dict_depth({})
    433        1
    434        >>> dict_depth({"a": "b"})
    435        1
    436        >>> dict_depth({"a": {}})
    437        2
    438        >>> dict_depth({"a": {"b": {}}})
    439        3
    440    """
    441    try:
    442        return 1 + dict_depth(next(iter(d.values())))
    443    except AttributeError:
    444        # d doesn't have attribute "values"
    445        return 0
    446    except StopIteration:
    447        # d.values() returns an empty sequence
    448        return 1

Get the nesting depth of a dictionary.

###### Example:

>     >>> dict_depth(None)
>     0
>     >>> dict_depth({})
>     1
>     >>> dict_depth({"a": "b"})
>     1
>     >>> dict_depth({"a": {}})
>     2
>     >>> dict_depth({"a": {"b": {}}})
>     3

def first(it: Iterable[~T]) -> ~T: View Source

    451def first(it: t.Iterable[T]) -> T:
    452    """Returns the first element from an iterable (useful for sets)."""
    453    return next(i for i in it)

Returns the first element from an iterable (useful for sets).

def merge_ranges(ranges: List[Tuple[~A, ~A]]) -> List[Tuple[~A, ~A]]: View Source

    456def merge_ranges(ranges: t.List[t.Tuple[A, A]]) -> t.List[t.Tuple[A, A]]:
    457    """
    458    Merges a sequence of ranges, represented as tuples (low, high) whose values
    459    belong to some totally-ordered set.
    460
    461    Example:
    462        >>> merge_ranges([(1, 3), (2, 6)])
    463        [(1, 6)]
    464    """
    465    if not ranges:
    466        return []
    467
    468    ranges = sorted(ranges)
    469
    470    merged = [ranges[0]]
    471
    472    for start, end in ranges[1:]:
    473        last_start, last_end = merged[-1]
    474
    475        if start <= last_end:
    476            merged[-1] = (last_start, max(last_end, end))
    477        else:
    478            merged.append((start, end))
    479
    480    return merged

Merges a sequence of ranges, represented as tuples (low, high) whose values belong to some totally-ordered set.

###### Example:

>     >>> merge_ranges([(1, 3), (2, 6)])
>     [(1, 6)]

def is_iso_date(text: str) -> bool: View Source

    483def is_iso_date(text: str) -> bool:
    484    try:
    485        datetime.date.fromisoformat(text)
    486        return True
    487    except ValueError:
    488        return False

def is_iso_datetime(text: str) -> bool: View Source

    491def is_iso_datetime(text: str) -> bool:
    492    try:
    493        datetime.datetime.fromisoformat(text)
    494        return True
    495    except ValueError:
    496        return False

DATE_UNITS = {'week', 'year_month', 'day', 'quarter', 'year', 'month'}
def is_date_unit(expression: Optional[sqlglot.expressions.Expression]) -> bool: View Source

    503def is_date_unit(expression: t.Optional[exp.Expression]) -> bool:
    504    return expression is not None and expression.name.lower() in DATE_UNITS

class SingleValuedMapping(typing.Mapping[~K, ~V]): View Source

    511class SingleValuedMapping(t.Mapping[K, V]):
    512    """
    513    Mapping where all keys return the same value.
    514
    515    This rigamarole is meant to avoid copying keys, which was originally intended
    516    as an optimization while qualifying columns for tables with lots of columns.
    517    """
    518
    519    def __init__(self, keys: t.Collection[K], value: V):
    520        self._keys = keys if isinstance(keys, Set) else set(keys)
    521        self._value = value
    522
    523    def __getitem__(self, key: K) -> V:
    524        if key in self._keys:
    525            return self._value
    526        raise KeyError(key)
    527
    528    def __len__(self) -> int:
    529        return len(self._keys)
    530
    531    def __iter__(self) -> t.Iterator[K]:
    532        return iter(self._keys)

Mapping where all keys return the same value.

This rigamarole is meant to avoid copying keys, which was originally intended as an optimization while qualifying columns for tables with lots of columns.

SingleValuedMapping(keys: Collection[~K], value: ~V) View Source

    519    def __init__(self, keys: t.Collection[K], value: V):
    520        self._keys = keys if isinstance(keys, Set) else set(keys)
    521        self._value = value

##### Inherited Members

collections.abc.Mapping
  get
  keys
  items
  values