Fix: prevent redundant backslash escapes in rawstring generator (#5040)

Author: georgesittas

sqlglot/generator.py

@@ -1349,7 +1349,11 @@ def unicodestring_sql(self, expression: exp.UnicodeString) -> str:
         return f"{left_quote}{this}{right_quote}{escape_sql}"
 
     def rawstring_sql(self, expression: exp.RawString) -> str:
-        string = self.escape_str(expression.this.replace("\\", "\\\\"), escape_backslash=False)
+        string = expression.this
+        if "\\" in self.dialect.tokenizer_class.STRING_ESCAPES:
+            string = string.replace("\\", "\\\\")
+
+        string = self.escape_str(string, escape_backslash=False)
         return f"{self.dialect.QUOTE_START}{string}{self.dialect.QUOTE_END}"
 
     def datatypeparam_sql(self, expression: exp.DataTypeParam) -> str:

tests/dialects/test_bigquery.py

@@ -236,6 +236,10 @@ def test_bigquery(self):
         self.validate_identity(
             "CREATE OR REPLACE VIEW test (tenant_id OPTIONS (description='Test description on table creation')) AS SELECT 1 AS tenant_id, 1 AS customer_id",
         )
+        self.validate_identity(
+            'SELECT r"\\t"',
+            "SELECT '\\\\t'",
+        )
         self.validate_identity(
             "ARRAY(SELECT AS STRUCT e.x AS y, e.z AS bla FROM UNNEST(bob))::ARRAY<STRUCT<y STRING, bro NUMERIC>>",
             "CAST(ARRAY(SELECT AS STRUCT e.x AS y, e.z AS bla FROM UNNEST(bob)) AS ARRAY<STRUCT<y STRING, bro NUMERIC>>)",
@@ -1023,8 +1027,8 @@ def test_bigquery(self):
             r'r"""/\*.*\*/"""',
             write={
                 "bigquery": r"'/\\*.*\\*/'",
-                "duckdb": r"'/\\*.*\\*/'",
-                "presto": r"'/\\*.*\\*/'",
+                "duckdb": r"'/\*.*\*/'",
+                "presto": r"'/\*.*\*/'",
                 "hive": r"'/\\*.*\\*/'",
                 "spark": r"'/\\*.*\\*/'",
             },
@@ -1033,8 +1037,8 @@ def test_bigquery(self):
             r'R"""/\*.*\*/"""',
             write={
                 "bigquery": r"'/\\*.*\\*/'",
-                "duckdb": r"'/\\*.*\\*/'",
-                "presto": r"'/\\*.*\\*/'",
+                "duckdb": r"'/\*.*\*/'",
+                "presto": r"'/\*.*\*/'",
                 "hive": r"'/\\*.*\\*/'",
                 "spark": r"'/\\*.*\\*/'",
             },