Feat(presto): transpile 'epoch' to '1970-01-01 00:00:00' in time-like…

… casts (#1726)
tobymao · Jun 6, 2023 · dd29f3f · dd29f3f
1 parent e4b164f
commit dd29f3f
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diff --git a/sqlglot/dialects/presto.py b/sqlglot/dialects/presto.py
@@ -272,6 +272,7 @@ class Generator(generator.Generator):
             exp.BitwiseOr: lambda self, e: f"BITWISE_OR({self.sql(e, 'this')}, {self.sql(e, 'expression')})",
             exp.BitwiseRightShift: lambda self, e: f"BITWISE_ARITHMETIC_SHIFT_RIGHT({self.sql(e, 'this')}, {self.sql(e, 'expression')})",
             exp.BitwiseXor: lambda self, e: f"BITWISE_XOR({self.sql(e, 'this')}, {self.sql(e, 'expression')})",
+            exp.Cast: transforms.preprocess([transforms.epoch_cast_to_ts]),
             exp.CurrentTimestamp: lambda *_: "CURRENT_TIMESTAMP",
             exp.DataType: _datatype_sql,
             exp.DateAdd: lambda self, e: self.func(
@@ -319,6 +320,7 @@ class Generator(generator.Generator):
             exp.TimeStrToUnix: lambda self, e: f"TO_UNIXTIME(DATE_PARSE({self.sql(e, 'this')}, {Presto.time_format}))",
             exp.TimeToStr: lambda self, e: f"DATE_FORMAT({self.sql(e, 'this')}, {self.format_time(e)})",
             exp.TimeToUnix: rename_func("TO_UNIXTIME"),
+            exp.TryCast: transforms.preprocess([transforms.epoch_cast_to_ts]),
             exp.TsOrDiToDi: lambda self, e: f"CAST(SUBSTR(REPLACE(CAST({self.sql(e, 'this')} AS VARCHAR), '-', ''), 1, 8) AS INT)",
             exp.TsOrDsAdd: _ts_or_ds_add_sql,
             exp.TsOrDsToDate: _ts_or_ds_to_date_sql,

diff --git a/sqlglot/transforms.py b/sqlglot/transforms.py
@@ -268,6 +268,17 @@ def add_recursive_cte_column_names(expression: exp.Expression) -> exp.Expression
     return expression
 
 
+def epoch_cast_to_ts(expression: exp.Expression) -> exp.Expression:
+    if (
+        isinstance(expression, (exp.Cast, exp.TryCast))
+        and expression.name.lower() == "epoch"
+        and expression.to.this in exp.DataType.TEMPORAL_TYPES
+    ):
+        expression.this.replace(exp.Literal.string("1970-01-01 00:00:00"))
+
+    return expression
+
+
 def preprocess(
     transforms: t.List[t.Callable[[exp.Expression], exp.Expression]],
 ) -> t.Callable[[Generator, exp.Expression], str]:

diff --git a/tests/dialects/test_presto.py b/tests/dialects/test_presto.py
@@ -6,6 +6,10 @@ class TestPresto(Validator):
     dialect = "presto"
 
     def test_cast(self):
+        self.validate_all(
+            "SELECT TRY_CAST('1970-01-01 00:00:00' AS TIMESTAMP)",
+            read={"postgres": "SELECT 'epoch'::TIMESTAMP"},
+        )
         self.validate_all(
             "FROM_BASE64(x)",
             read={