feat(sqlglot): Vertica dialect (#39969)

superset/sql/dialects/vertica.py

@@ -0,0 +1,87 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+"""
+Vertica dialect.
+
+Vertica is wire-compatible with PostgreSQL but provides additional analytical
+functions natively. This dialect extends the Postgres dialect to preserve
+Vertica-native functions that the Postgres generator would otherwise rewrite.
+"""
+
+from __future__ import annotations
+
+from sqlglot import exp
+from sqlglot.dialects.dialect import date_delta_sql
+from sqlglot.dialects.postgres import Postgres
+from sqlglot.helper import seq_get
+
+
+def _build_datediff(args: list[exp.Expression]) -> exp.DateDiff:
+    # Vertica's signature is DATEDIFF(unit, start, end); the default sqlglot
+    # parser assumes (end, start, unit), so we remap the positional args.
+    return exp.DateDiff(
+        this=seq_get(args, 2),
+        expression=seq_get(args, 1),
+        unit=exp.var(seq_get(args, 0).name) if seq_get(args, 0) else None,
+    )
+
+
+class Vertica(Postgres):
+    """
+    Vertica dialect.
+
+    Extends PostgreSQL by keeping functions that Vertica supports natively but
+    Postgres does not (e.g. ``LAST_DAY``, ``DATEDIFF``, ``MEDIAN``, ``NVL2``).
+    """
+
+    class Parser(Postgres.Parser):
+        FUNCTIONS = {
+            **Postgres.Parser.FUNCTIONS,
+            "DATEDIFF": _build_datediff,
+            "TIMESTAMPDIFF": _build_datediff,
+        }
+
+    class Generator(Postgres.Generator):
+        # Vertica's LAST_DAY only accepts a date/timestamp; it does not take a
+        # date part argument like Snowflake's variant.
+        LAST_DAY_SUPPORTS_DATE_PART = False
+
+        # Vertica supports MEDIAN and NVL2 natively; Postgres does not, and the
+        # inherited generator rewrites them into PERCENTILE_CONT and CASE
+        # expressions respectively.
+        SUPPORTS_MEDIAN = True
+        NVL2_SUPPORTED = True
+
+        # Emit INTERVAL '<value>' <unit> (SQL-standard) instead of the
+        # Postgres-style INTERVAL '<value> <unit>'. Vertica miscomputes the
+        # combined-string form for MONTH/YEAR units (treats them as a fixed
+        # number of days). See https://forum.vertica.com/discussion/229329/.
+        SINGLE_STRING_INTERVAL = False
+
+        TRANSFORMS = {
+            **Postgres.Generator.TRANSFORMS,
+            # Postgres rewrites LAST_DAY into DATE_TRUNC + INTERVAL arithmetic
+            # because it lacks the function. Vertica supports it natively, so
+            # drop the rewrite and fall back to the base lastday_sql.
+            exp.LastDay: lambda self, e: self.function_fallback_sql(e),
+            # Postgres rewrites DATEDIFF into EXTRACT(epoch ...) / AGE() math.
+            # Vertica's native form is DATEDIFF(unit, start, end), matching
+            # Snowflake's signature.
+            exp.DateDiff: date_delta_sql("DATEDIFF"),
+            exp.TsOrDsDiff: date_delta_sql("DATEDIFF"),
+        }