# sqlglot.helper API documentation

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# sqlglot.helper

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      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    if t.cast(exp.DataType, expression.type).this in exp.DataType.INTEGER_TYPES:
    183        logger.warning("Applying array index offset (%s)", offset)
    184        expression = simplify(expression + offset)
    185        return [expression]
    186
    187    return expressions
    188
    189
    190def camel_to_snake_case(name: str) -> str:
    191    """Converts `name` from camelCase to snake_case and returns the result."""
    192    return CAMEL_CASE_PATTERN.sub("_", name).upper()
    193
    194
    195def while_changing(expression: Expression, func: t.Callable[[Expression], E]) -> E:
    196    """
    197    Applies a transformation to a given expression until a fix point is reached.
    198
    199    Args:
    200        expression: The expression to be transformed.
    201        func: The transformation to be applied.
    202
    203    Returns:
    204        The transformed expression.
    205    """
    206    while True:
    207        for n in reversed(tuple(expression.walk())):
    208            n._hash = hash(n)
    209
    210        start = hash(expression)
    211        expression = func(expression)
    212
    213        for n in expression.walk():
    214            n._hash = None
    215        if start == hash(expression):
    216            break
    217
    218    return expression
    219
    220
    221def tsort(dag: t.Dict[T, t.Set[T]]) -> t.List[T]:
    222    """
    223    Sorts a given directed acyclic graph in topological order.
    224
    225    Args:
    226        dag: The graph to be sorted.
    227
    228    Returns:
    229        A list that contains all of the graph's nodes in topological order.
    230    """
    231    result = []
    232
    233    for node, deps in tuple(dag.items()):
    234        for dep in deps:
    235            if dep not in dag:
    236                dag[dep] = set()
    237
    238    while dag:
    239        current = {node for node, deps in dag.items() if not deps}
    240
    241        if not current:
    242            raise ValueError("Cycle error")
    243
    244        for node in current:
    245            dag.pop(node)
    246
    247        for deps in dag.values():
    248            deps -= current
    249
    250        result.extend(sorted(current))  # type: ignore
    251
    252    return result
    253
    254
    255def open_file(file_name: str) -> t.TextIO:
    256    """Open a file that may be compressed as gzip and return it in universal newline mode."""
    257    with open(file_name, "rb") as f:
    258        gzipped = f.read(2) == b"\x1f\x8b"
    259
    260    if gzipped:
    261        import gzip
    262
    263        return gzip.open(file_name, "rt", newline="")
    264
    265    return open(file_name, encoding="utf-8", newline="")
    266
    267
    268@contextmanager
    269def csv_reader(read_csv: exp.ReadCSV) -> t.Any:
    270    """
    271    Returns a csv reader given the expression `READ_CSV(name, ['delimiter', '|', ...])`.
    272
    273    Args:
    274        read_csv: A `ReadCSV` function call.
    275
    276    Yields:
    277        A python csv reader.
    278    """
    279    args = read_csv.expressions
    280    file = open_file(read_csv.name)
    281
    282    delimiter = ","
    283    args = iter(arg.name for arg in args)  # type: ignore
    284    for k, v in zip(args, args):
    285        if k == "delimiter":
    286            delimiter = v
    287
    288    try:
    289        import csv as csv_
    290
    291        yield csv_.reader(file, delimiter=delimiter)
    292    finally:
    293        file.close()
    294
    295
    296def find_new_name(taken: t.Collection[str], base: str) -> str:
    297    """
    298    Searches for a new name.
    299
    300    Args:
    301        taken: A collection of taken names.
    302        base: Base name to alter.
    303
    304    Returns:
    305        The new, available name.
    306    """
    307    if base not in taken:
    308        return base
    309
    310    i = 2
    311    new = f"{base}_{i}"
    312    while new in taken:
    313        i += 1
    314        new = f"{base}_{i}"
    315
    316    return new
    317
    318
    319def is_int(text: str) -> bool:
    320    return is_type(text, int)
    321
    322
    323def is_float(text: str) -> bool:
    324    return is_type(text, float)
    325
    326
    327def is_type(text: str, target_type: t.Type) -> bool:
    328    try:
    329        target_type(text)
    330        return True
    331    except ValueError:
    332        return False
    333
    334
    335def name_sequence(prefix: str) -> t.Callable[[], str]:
    336    """Returns a name generator given a prefix (e.g. a0, a1, a2, ... if the prefix is "a")."""
    337    sequence = count()
    338    return lambda: f"{prefix}{next(sequence)}"
    339
    340
    341def object_to_dict(obj: t.Any, **kwargs) -> t.Dict:
    342    """Returns a dictionary created from an object's attributes."""
    343    return {
    344        **{k: v.copy() if hasattr(v, "copy") else copy(v) for k, v in vars(obj).items()},
    345        **kwargs,
    346    }
    347
    348
    349def split_num_words(
    350    value: str, sep: str, min_num_words: int, fill_from_start: bool = True
    351) -> t.List[t.Optional[str]]:
    352    """
    353    Perform a split on a value and return N words as a result with `None` used for words that don't exist.
    354
    355    Args:
    356        value: The value to be split.
    357        sep: The value to use to split on.
    358        min_num_words: The minimum number of words that are going to be in the result.
    359        fill_from_start: Indicates that if `None` values should be inserted at the start or end of the list.
    360
    361    Examples:
    362        >>> split_num_words("db.table", ".", 3)
    363        [None, 'db', 'table']
    364        >>> split_num_words("db.table", ".", 3, fill_from_start=False)
    365        ['db', 'table', None]
    366        >>> split_num_words("db.table", ".", 1)
    367        ['db', 'table']
    368
    369    Returns:
    370        The list of words returned by `split`, possibly augmented by a number of `None` values.
    371    """
    372    words = value.split(sep)
    373    if fill_from_start:
    374        return [None] * (min_num_words - len(words)) + words
    375    return words + [None] * (min_num_words - len(words))
    376
    377
    378def is_iterable(value: t.Any) -> bool:
    379    """
    380    Checks if the value is an iterable, excluding the types `str` and `bytes`.
    381
    382    Examples:
    383        >>> is_iterable([1,2])
    384        True
    385        >>> is_iterable("test")
    386        False
    387
    388    Args:
    389        value: The value to check if it is an iterable.
    390
    391    Returns:
    392        A `bool` value indicating if it is an iterable.
    393    """
    394    from sqlglot import Expression
    395
    396    return hasattr(value, "__iter__") and not isinstance(value, (str, bytes, Expression))
    397
    398
    399def flatten(values: t.Iterable[t.Iterable[t.Any] | t.Any]) -> t.Iterator[t.Any]:
    400    """
    401    Flattens an iterable that can contain both iterable and non-iterable elements. Objects of
    402    type `str` and `bytes` are not regarded as iterables.
    403
    404    Examples:
    405        >>> list(flatten([[1, 2], 3, {4}, (5, "bla")]))
    406        [1, 2, 3, 4, 5, 'bla']
    407        >>> list(flatten([1, 2, 3]))
    408        [1, 2, 3]
    409
    410    Args:
    411        values: The value to be flattened.
    412
    413    Yields:
    414        Non-iterable elements in `values`.
    415    """
    416    for value in values:
    417        if is_iterable(value):
    418            yield from flatten(value)
    419        else:
    420            yield value
    421
    422
    423def dict_depth(d: t.Dict) -> int:
    424    """
    425    Get the nesting depth of a dictionary.
    426
    427    Example:
    428        >>> dict_depth(None)
    429        0
    430        >>> dict_depth({})
    431        1
    432        >>> dict_depth({"a": "b"})
    433        1
    434        >>> dict_depth({"a": {}})
    435        2
    436        >>> dict_depth({"a": {"b": {}}})
    437        3
    438    """
    439    try:
    440        return 1 + dict_depth(next(iter(d.values())))
    441    except AttributeError:
    442        # d doesn't have attribute "values"
    443        return 0
    444    except StopIteration:
    445        # d.values() returns an empty sequence
    446        return 1
    447
    448
    449def first(it: t.Iterable[T]) -> T:
    450    """Returns the first element from an iterable (useful for sets)."""
    451    return next(i for i in it)
    452
    453
    454def merge_ranges(ranges: t.List[t.Tuple[A, A]]) -> t.List[t.Tuple[A, A]]:
    455    """
    456    Merges a sequence of ranges, represented as tuples (low, high) whose values
    457    belong to some totally-ordered set.
    458
    459    Example:
    460        >>> merge_ranges([(1, 3), (2, 6)])
    461        [(1, 6)]
    462    """
    463    if not ranges:
    464        return []
    465
    466    ranges = sorted(ranges)
    467
    468    merged = [ranges[0]]
    469
    470    for start, end in ranges[1:]:
    471        last_start, last_end = merged[-1]
    472
    473        if start <= last_end:
    474            merged[-1] = (last_start, max(last_end, end))
    475        else:
    476            merged.append((start, end))
    477
    478    return merged
    479
    480
    481def is_iso_date(text: str) -> bool:
    482    try:
    483        datetime.date.fromisoformat(text)
    484        return True
    485    except ValueError:
    486        return False
    487
    488
    489def is_iso_datetime(text: str) -> bool:
    490    try:
    491        datetime.datetime.fromisoformat(text)
    492        return True
    493    except ValueError:
    494        return False
    495
    496
    497# Interval units that operate on date components
    498DATE_UNITS = {"day", "week", "month", "quarter", "year", "year_month"}
    499
    500
    501def is_date_unit(expression: t.Optional[exp.Expression]) -> bool:
    502    return expression is not None and expression.name.lower() in DATE_UNITS
    503
    504
    505K = t.TypeVar("K")
    506V = t.TypeVar("V")
    507
    508
    509class SingleValuedMapping(t.Mapping[K, V]):
    510    """
    511    Mapping where all keys return the same value.
    512
    513    This rigamarole is meant to avoid copying keys, which was originally intended
    514    as an optimization while qualifying columns for tables with lots of columns.
    515    """
    516
    517    def __init__(self, keys: t.Collection[K], value: V):
    518        self._keys = keys if isinstance(keys, Set) else set(keys)
    519        self._value = value
    520
    521    def __getitem__(self, key: K) -> V:
    522        if key in self._keys:
    523            return self._value
    524        raise KeyError(key)
    525
    526    def __len__(self) -> int:
    527        return len(self._keys)
    528
    529    def __iter__(self) -> t.Iterator[K]:
    530        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    if t.cast(exp.DataType, expression.type).this in exp.DataType.INTEGER_TYPES:
    184        logger.warning("Applying array index offset (%s)", offset)
    185        expression = simplify(expression + offset)
    186        return [expression]
    187
    188    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

    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()

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

    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

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

    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

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

    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="")

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

    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()

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

    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

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

    320def is_int(text: str) -> bool:
    321    return is_type(text, int)

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

    324def is_float(text: str) -> bool:
    325    return is_type(text, float)

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

    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

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

    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)}"

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

    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    }

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

    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))

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

    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))

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

    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

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

    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

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

    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)

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

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

    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

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

    482def is_iso_date(text: str) -> bool:
    483    try:
    484        datetime.date.fromisoformat(text)
    485        return True
    486    except ValueError:
    487        return False

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

    490def is_iso_datetime(text: str) -> bool:
    491    try:
    492        datetime.datetime.fromisoformat(text)
    493        return True
    494    except ValueError:
    495        return False

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

    502def is_date_unit(expression: t.Optional[exp.Expression]) -> bool:
    503    return expression is not None and expression.name.lower() in DATE_UNITS

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

    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)

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

    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

##### Inherited Members

collections.abc.Mapping
  get
  keys
  items
  values