feat(snowflake): support invoking dynamically-resolved functions via IDENTIFIER() (#7796)

* feat(snowflake): support invoking dynamically-resolved functions via IDENTIFIER()

* call unsupported to not naively emit function calls

Author: eruditmorina

sqlglot/expressions/core.py

@@ -10,12 +10,14 @@
 import sys
 import textwrap
 import typing as t
+from builtins import type as Type
 from collections import deque
+from collections.abc import Collection, Iterator, Mapping, MutableMapping, Sequence
 from copy import deepcopy
 from decimal import Decimal
 from functools import reduce
-from collections.abc import Iterator, Sequence, Collection, Mapping, MutableMapping
-from sqlglot._typing import E, T
+
+from sqlglot._typing import E, GeneratorNoDialectArgs, ParserNoDialectArgs, T
 from sqlglot.errors import ParseError
 from sqlglot.helper import (
     camel_to_snake_case,
@@ -24,17 +26,15 @@
     to_bool,
     trait,
 )
-
 from sqlglot.tokenizer_core import Token
-from builtins import type as Type
-from sqlglot._typing import GeneratorNoDialectArgs, ParserNoDialectArgs
 
 if t.TYPE_CHECKING:
-    from typing_extensions import Self, Unpack, Concatenate
+    from typing_extensions import Concatenate, Self, Unpack
+
+    from sqlglot._typing import P
     from sqlglot.dialects.dialect import DialectType
     from sqlglot.expressions.datatypes import DATA_TYPE, DataType, DType, Interval
     from sqlglot.expressions.query import Select
-    from sqlglot._typing import P
 
     R = t.TypeVar("R")
 
@@ -1808,8 +1808,10 @@ def output_name(self) -> str:
 
 
 # https://docs.snowflake.com/en/sql-reference/identifier-literal
+# "expressions" holds the arguments when the resolved identifier is invoked as a
+# function, e.g. `IDENTIFIER('my_func')(1, 2)`
 class DynamicIdentifier(Expression, Func):
-    pass
+    arg_types = {"this": True, "expressions": False}
 
 
 class Opclass(Expression):
@@ -2425,7 +2427,8 @@ def convert(value: t.Any, copy: bool = False) -> Expr:
 
         return _Array(expressions=[convert(v, copy=copy) for v in value])
     if isinstance(value, dict):
-        from sqlglot.expressions.array import Array as _Array, Map as _Map
+        from sqlglot.expressions.array import Array as _Array
+        from sqlglot.expressions.array import Map as _Map
 
         return _Map(
             keys=_Array(expressions=[convert(k, copy=copy) for k in value]),

sqlglot/generator.py

@@ -1960,7 +1960,14 @@ def index_sql(self, expression: exp.Index) -> str:
     def dynamicidentifier_sql(self, expression: exp.DynamicIdentifier) -> str:
         this = expression.this
         if this and this.is_string:
-            return maybe_parse(this.name).sql(self.dialect)
+            resolved = maybe_parse(this.name).sql(self.dialect)
+            if "expressions" in expression.args:
+                # `IDENTIFIER(...)` invoked as a function, e.g. `IDENTIFIER('my_func')(1, 2)`
+                # We can't safely emit the call to other dialects since name/arg semantics may differ
+                self.unsupported(
+                    "Transpiling dynamically-invoked IDENTIFIER() functions is unsupported"
+                )
+            return resolved
         self.unsupported("IDENTIFIER() with non-literal arguments is not supported")
         return self.func("IDENTIFIER", this)
 

sqlglot/generators/snowflake.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import typing as t
+from collections import defaultdict
 
 from sqlglot import exp, generator, transforms
 from sqlglot.dialects.dialect import (
@@ -34,7 +35,6 @@
     build_object_construct,
 )
 from sqlglot.tokens import TokenType
-from collections import defaultdict
 
 if t.TYPE_CHECKING:
     from sqlglot._typing import E
@@ -475,7 +475,6 @@ class SnowflakeGenerator(generator.Generator):
         exp.DayOfWeekIso: rename_func("DAYOFWEEKISO"),
         exp.DayOfYear: rename_func("DAYOFYEAR"),
         exp.DotProduct: rename_func("VECTOR_INNER_PRODUCT"),
-        exp.DynamicIdentifier: rename_func("IDENTIFIER"),
         exp.Explode: rename_func("FLATTEN"),
         exp.Extract: lambda self, e: self.func(
             "DATE_PART", map_date_part(e.this, self.dialect), e.expression
@@ -617,6 +616,13 @@ class SnowflakeGenerator(generator.Generator):
         ),
     }
 
+    def dynamicidentifier_sql(self, expression: exp.DynamicIdentifier) -> str:
+        this = self.func("IDENTIFIER", expression.this)
+        if "expressions" in expression.args:
+            # `IDENTIFIER(...)` invoked as a function, e.g. `IDENTIFIER('my_func')(1, 2)`
+            return self.func(this, *expression.expressions, normalize=False)
+        return this
+
     def sortarray_sql(self, expression: exp.SortArray) -> str:
         asc = expression.args.get("asc")
         nulls_first = expression.args.get("nulls_first")

sqlglot/parsers/snowflake.py

@@ -1156,6 +1156,31 @@ def _parse_table(
 
         return table
 
+    def _parse_function_call(
+        self,
+        functions: dict[str, t.Callable] | None = None,
+        anonymous: bool = False,
+        optional_parens: bool = True,
+        any_token: bool = False,
+    ) -> exp.Expr | None:
+        this = super()._parse_function_call(
+            functions=functions,
+            anonymous=anonymous,
+            optional_parens=optional_parens,
+            any_token=any_token,
+        )
+
+        # Snowflake can invoke a function whose name is dynamically resolved, e.g.
+        # `IDENTIFIER('my_func')(1, 2)`. The trailing argument list is the call's arguments.
+        #
+        # https://docs.snowflake.com/en/sql-reference/identifier-literal
+        if isinstance(this, exp.DynamicIdentifier) and self._match(
+            TokenType.L_PAREN, advance=False
+        ):
+            this.set("expressions", self._parse_wrapped_csv(self._parse_lambda))
+
+        return this
+
     def _parse_id_var(
         self,
         any_token: bool = True,

tests/dialects/test_snowflake.py

@@ -769,6 +769,15 @@ def test_snowflake(self):
         self.validate_identity("SELECT KURTOSIS(x) OVER (PARTITION BY 1)")
         self.validate_identity("WITH x AS (SELECT 1 AS foo) SELECT foo FROM IDENTIFIER('x')")
         self.validate_identity("WITH x AS (SELECT 1 AS foo) SELECT IDENTIFIER('foo') FROM x")
+        self.validate_identity("SELECT IDENTIFIER($my_function_name)()")
+        self.validate_identity("SELECT IDENTIFIER('speed_of_light')()")
+        self.validate_all(
+            "SELECT IDENTIFIER('my_func')(1, 2)",
+            write={
+                "snowflake": "SELECT IDENTIFIER('my_func')(1, 2)",
+                "duckdb": UnsupportedError,
+            },
+        )
         self.validate_identity("INITCAP('iqamqinterestedqinqthisqtopic', 'q')")
         self.validate_identity("OBJECT_CONSTRUCT(*)")
         self.validate_identity("SELECT CAST('2021-01-01' AS DATE) + INTERVAL '1 DAY'")