Small fixes

superset/db_engine_specs/base.py

@@ -557,6 +557,12 @@ class BaseEngineSpec:  # pylint: disable=too-many-public-methods
     # if True, database will be listed as option in the upload file form
     supports_file_upload = True
 
+    # RLS strategy for this engine spec. Override in engine-specific classes as
+    # needed (for example ``RLSMethod.AS_PREDICATE`` for engines that don't
+    # support subquery-based RLS, or ``RLSMethod.AS_PREDICATE_SPLICE`` for
+    # engines where sqlglot generation is not faithful).
+    rls_method = RLSMethod.AS_SUBQUERY
+
     # Is the DB engine spec able to change the default schema? This requires implementing  # noqa: E501
     # a custom `adjust_engine_params` method.
     supports_dynamic_schema = False
@@ -618,21 +624,6 @@ class BaseEngineSpec:  # pylint: disable=too-many-public-methods
             else cls.encrypted_extra_sensitive_fields
         )
 
-    @classmethod
-    def get_rls_method(cls) -> RLSMethod:
-        """
-        Returns the RLS method to be used for this engine.
-
-        There are two ways to insert RLS: either replacing the table with a subquery
-        that has the RLS, or appending the RLS to the ``WHERE`` clause. The former is
-        safer, but not supported in all databases.
-        """
-        return (
-            RLSMethod.AS_SUBQUERY
-            if cls.allows_subqueries and cls.allows_alias_in_select
-            else RLSMethod.AS_PREDICATE
-        )
-
     @classmethod
     def is_oauth2_enabled(cls) -> bool:
         return (

superset/db_engine_specs/couchbase.py

@@ -35,6 +35,7 @@ from superset.db_engine_specs.base import (
     DatabaseCategory,
 )
 from superset.errors import ErrorLevel, SupersetError, SupersetErrorType
+from superset.sql.parse import RLSMethod
 from superset.utils.network import is_hostname_valid, is_port_open
 
 
@@ -82,6 +83,7 @@ class CouchbaseEngineSpec(BasicParametersMixin, BaseEngineSpec):
     default_driver = "couchbase"
     allows_joins = False
     allows_subqueries = False
+    rls_method = RLSMethod.AS_PREDICATE
     sqlalchemy_uri_placeholder = (
         "couchbase://user:password@host[:port]?truststorepath=value?ssl=value"
     )

superset/db_engine_specs/crate.py

@@ -23,6 +23,7 @@ from sqlalchemy import types
 
 from superset.constants import TimeGrain
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
+from superset.sql.parse import RLSMethod
 
 if TYPE_CHECKING:
     from superset.connectors.sqla.models import TableColumn
@@ -68,6 +69,8 @@ class CrateEngineSpec(BaseEngineSpec):
         TimeGrain.YEAR: "DATE_TRUNC('year', {col})",
     }
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     @classmethod
     def epoch_to_dttm(cls) -> str:
         return "{col} * 1000"

superset/db_engine_specs/databend.py

@@ -39,6 +39,7 @@ from superset.db_engine_specs.base import (
 )
 from superset.db_engine_specs.exceptions import SupersetDBAPIDatabaseError
 from superset.errors import ErrorLevel, SupersetError, SupersetErrorType
+from superset.sql.parse import RLSMethod
 from superset.utils.core import GenericDataType
 from superset.utils.hashing import hash_from_str
 from superset.utils.network import is_hostname_valid, is_port_open
@@ -55,6 +56,8 @@ class DatabendBaseEngineSpec(BaseEngineSpec):
     time_secondary_columns = True
     time_groupby_inline = True
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     _time_grain_expressions = {
         None: "{col}",
         TimeGrain.SECOND: "DATE_TRUNC('SECOND', {col})",

superset/db_engine_specs/denodo.py

@@ -26,6 +26,7 @@ from superset.db_engine_specs.base import (
     DatabaseCategory,
 )
 from superset.errors import SupersetErrorType
+from superset.sql.parse import RLSMethod
 
 
 # Internal class for defining error message patterns (for translation)
@@ -58,6 +59,8 @@ class DenodoEngineSpec(BaseEngineSpec, BasicParametersMixin):
     engine = "denodo"
     engine_name = "Denodo"
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     default_driver = "psycopg2"
     sqlalchemy_uri_placeholder = (
         "denodo://user:password@host:port/dbname[?key=value&key=value...]"

superset/db_engine_specs/dynamodb.py

@@ -21,12 +21,15 @@ from sqlalchemy import types
 
 from superset.constants import TimeGrain
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
+from superset.sql.parse import RLSMethod
 
 
 class DynamoDBEngineSpec(BaseEngineSpec):
     engine = "dynamodb"
     engine_name = "Amazon DynamoDB"
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     metadata = {
         "description": (
             "Amazon DynamoDB is a serverless NoSQL database with SQL via PartiQL."

superset/db_engine_specs/elasticsearch.py

@@ -28,6 +28,7 @@ from superset.db_engine_specs.exceptions import (
     SupersetDBAPIOperationalError,
     SupersetDBAPIProgrammingError,
 )
+from superset.sql.parse import RLSMethod
 
 logger = logging.getLogger()
 
@@ -39,6 +40,7 @@ class ElasticSearchEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-metho
     allows_joins = False
     allows_subqueries = True
     allows_sql_comments = False
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
 
     metadata = {
         "description": (

superset/db_engine_specs/firebird.py

@@ -21,7 +21,7 @@ from sqlalchemy import types
 
 from superset.constants import TimeGrain
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
-from superset.sql.parse import LimitMethod
+from superset.sql.parse import LimitMethod, RLSMethod
 
 
 class FirebirdEngineSpec(BaseEngineSpec):
@@ -53,6 +53,8 @@ class FirebirdEngineSpec(BaseEngineSpec):
     # Firebird uses FIRST to limit: `SELECT FIRST 10 * FROM table`
     limit_method = LimitMethod.FETCH_MANY
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     _time_grain_expressions = {
         None: "{col}",
         TimeGrain.SECOND: (

superset/db_engine_specs/ibmi.py

@@ -14,6 +14,8 @@
 # KIND, either express or implied.  See the License for the
 # specific language governing permissions and limitations
 # under the License.
+from superset.sql.parse import RLSMethod
+
 from .db2 import Db2EngineSpec
 
 
@@ -28,6 +30,8 @@ class IBMiEngineSpec(Db2EngineSpec):
     engine_name = "IBM Db2 for i"
     max_column_name_length = 128
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     @classmethod
     def epoch_to_dttm(cls) -> str:
         return "(DAYS({col}) - DAYS('1970-01-01')) * 86400 + MIDNIGHT_SECONDS({col})"

superset/db_engine_specs/kusto.py

@@ -28,7 +28,7 @@ from superset.db_engine_specs.exceptions import (
     SupersetDBAPIOperationalError,
     SupersetDBAPIProgrammingError,
 )
-from superset.sql.parse import LimitMethod
+from superset.sql.parse import LimitMethod, RLSMethod
 from superset.utils.core import GenericDataType
 
 
@@ -40,6 +40,7 @@ class KustoSqlEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-method
     allows_joins = True
     allows_subqueries = True
     allows_sql_comments = False
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
 
     metadata = {
         "description": (

superset/db_engine_specs/kylin.py

@@ -21,6 +21,7 @@ from sqlalchemy import types
 
 from superset.constants import TimeGrain
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
+from superset.sql.parse import RLSMethod
 
 
 class KylinEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-method
@@ -29,6 +30,8 @@ class KylinEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-method
     engine = "kylin"
     engine_name = "Apache Kylin"
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     metadata = {
         "description": "Apache Kylin is an open-source OLAP engine for big data.",
         "logo": "apache-kylin.png",

superset/db_engine_specs/ocient.py

@@ -39,6 +39,7 @@ from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
 from superset.errors import SupersetErrorType
 from superset.models.core import Database
 from superset.models.sql_lab import Query
+from superset.sql.parse import RLSMethod
 
 # Regular expressions to catch custom errors
 
@@ -227,6 +228,8 @@ class OcientEngineSpec(BaseEngineSpec):
     force_column_alias_quotes = True
     max_column_name_length = 30
 
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
+
     allows_cte_in_subquery = False
     # Ocient does not support cte names starting with underscores
     cte_alias = "cte__"

superset/db_engine_specs/pinot.py

@@ -20,6 +20,7 @@ from sqlalchemy.types import TypeEngine
 
 from superset.constants import TimeGrain
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
+from superset.sql.parse import RLSMethod
 
 
 class PinotEngineSpec(BaseEngineSpec):
@@ -30,6 +31,7 @@ class PinotEngineSpec(BaseEngineSpec):
     allows_joins = False
     allows_alias_in_select = False
     allows_alias_in_orderby = False
+    rls_method = RLSMethod.AS_PREDICATE
 
     # pinotdb only sets cursor.description when the response contains
     # columnDataTypes, which Pinot omits for zero-row results.

superset/db_engine_specs/solr.py

@@ -16,6 +16,7 @@
 # under the License.
 
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
+from superset.sql.parse import RLSMethod
 
 
 class SolrEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-method
@@ -27,6 +28,7 @@ class SolrEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-method
     time_groupby_inline = False
     allows_joins = False
     allows_subqueries = False
+    rls_method = RLSMethod.AS_PREDICATE
 
     metadata = {
         "description": "Apache Solr is an open-source enterprise search platform.",

superset/db_engine_specs/tdengine.py

@@ -22,6 +22,7 @@ from urllib import parse
 from sqlalchemy.engine.url import make_url, URL  # noqa: F401
 
 from superset.db_engine_specs.base import BaseEngineSpec, DatabaseCategory
+from superset.sql.parse import RLSMethod
 
 
 class TDengineEngineSpec(BaseEngineSpec):
@@ -29,6 +30,8 @@ class TDengineEngineSpec(BaseEngineSpec):
     engine_name = "TDengine"
     max_column_name_length = 64
     default_driver = "taosws"
+
+    rls_method = RLSMethod.AS_PREDICATE_SPLICE
     sqlalchemy_uri_placeholder = (
         "taosws://user:******@host:port/dbname[?key=value&key=value...]"
     )

superset/sql/parse.py

@@ -76,7 +76,7 @@ SQLGLOT_DIALECTS = {
     "duckdb": Dialects.DUCKDB,
     # "dynamodb": ???
     # "elasticsearch": ???
-    # "exa": ???
+    "exa": Dialects.EXASOL,
     # "firebird": ???
     "firebolt": Firebolt,
     "gsheets": Dialects.SQLITE,
@@ -105,7 +105,7 @@ SQLGLOT_DIALECTS = {
     "shillelagh": Dialects.SQLITE,
     "singlestoredb": SingleStore,
     "snowflake": Dialects.SNOWFLAKE,
-    # "solr": ???
+    "solr": Dialects.SOLR,
     "spark": Dialects.SPARK,
     "sqlite": Dialects.SQLITE,
     "starrocks": Dialects.STARROCKS,
@@ -142,6 +142,7 @@ class RLSMethod(enum.Enum):
 
     AS_PREDICATE = enum.auto()
     AS_SUBQUERY = enum.auto()
+    AS_PREDICATE_SPLICE = enum.auto()
 
 
 class RLSTransformer:
@@ -355,6 +356,7 @@ class BaseSQLStatement(Generic[InternalRepresentation]):
         statement: str | None = None,
         engine: str = "base",
         ast: InternalRepresentation | None = None,
+        source: str | None = None,
     ):
         if ast:
             self._parsed = ast
@@ -365,6 +367,16 @@ class BaseSQLStatement(Generic[InternalRepresentation]):
 
         self.engine = engine
         self.tables = self._extract_tables_from_statement(self._parsed, self.engine)
+        # Original SQL substring for this statement, when known. Used by the
+        # splice-mode RLS path which rewrites this string instead of regenerating
+        # SQL from the AST. ``None`` means the statement was constructed from an
+        # AST without an associated source string (splice mode falls back).
+        self._source_sql: str | None = source if source is not None else statement
+        # Verbatim SQL to return from ``format()``. Set by string-rewriting
+        # operations (e.g. splice-mode RLS) that produce a final SQL string and
+        # need to bypass the dialect generator. Cleared by AST-mutating methods
+        # since those invalidate this cached text.
+        self._raw_sql: str | None = None
 
     @classmethod
     def split_script(
@@ -531,7 +543,7 @@ class BaseSQLStatement(Generic[InternalRepresentation]):
         self,
         catalog: str | None,
         schema: str | None,
-        predicates: dict[Table, list[InternalRepresentation]],
+        predicates: dict[Table, list[str]],
         method: RLSMethod,
     ) -> None:
         """
@@ -559,9 +571,10 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
         statement: str | None = None,
         engine: str = "base",
         ast: exp.Expression | None = None,
+        source: str | None = None,
     ):
         self._dialect = SQLGLOT_DIALECTS.get(engine)
-        super().__init__(statement, engine, ast)
+        super().__init__(statement, engine, ast, source)
 
     @classmethod
     def _parse(cls, script: str, engine: str) -> list[exp.Expression]:
@@ -626,10 +639,57 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
         script: str,
         engine: str,
     ) -> list[SQLStatement]:
+        asts = [ast for ast in cls._parse(script, engine) if ast]
+        sources = cls._split_source(script, engine, len(asts))
         return [
-            cls(ast=ast, engine=engine) for ast in cls._parse(script, engine) if ast
+            cls(ast=ast, engine=engine, source=source)
+            for ast, source in zip(asts, sources, strict=True)
         ]
 
+    @classmethod
+    def _split_source(
+        cls,
+        script: str,
+        engine: str,
+        expected_count: int,
+    ) -> list[str | None]:
+        """
+        Slice ``script`` into per-statement substrings using top-level semicolon
+        positions from the tokenizer. Returns a list of length ``expected_count``;
+        any entry is ``None`` if the slicing didn't yield a usable substring.
+
+        The returned substrings preserve the original byte content of the script
+        for each statement — necessary for splice-mode RLS, which rewrites the
+        original SQL rather than regenerating from the AST.
+        """
+        none_result: list[str | None] = [None] * expected_count
+        dialect = SQLGLOT_DIALECTS.get(engine)
+        try:
+            tokens = list(Dialect.get_or_raise(dialect).tokenize(script))
+        except sqlglot.errors.SqlglotError:
+            return none_result
+
+        # Top-level semicolon offsets (depth 0).
+        boundaries: list[int] = []
+        depth = 0
+        for tok in tokens:
+            if tok.token_type == sqlglot.tokens.TokenType.L_PAREN:
+                depth += 1
+            elif tok.token_type == sqlglot.tokens.TokenType.R_PAREN:
+                # Clamp at 0 so malformed SQL with unbalanced ')' can't drive
+                # depth negative and misclassify later semicolons as nested.
+                depth = max(0, depth - 1)
+            elif tok.token_type == sqlglot.tokens.TokenType.SEMICOLON and depth == 0:
+                boundaries.append(tok.start)
+
+        starts = [0, *(b + 1 for b in boundaries)]
+        ends = [*boundaries, len(script)]
+        sources = [script[s:e].strip() for s, e in zip(starts, ends, strict=True)]
+        sources = [s for s in sources if s]
+        if len(sources) != expected_count:
+            return none_result
+        return list(sources)
+
     @classmethod
     def _parse_statement(
         cls,
@@ -722,7 +782,13 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
     def format(self, comments: bool = True) -> str:
         """
         Pretty-format the SQL statement.
+
+        When a string-rewriting operation (e.g. splice-mode RLS) has cached a
+        verbatim result in ``_raw_sql``, return it as-is — the whole point of
+        those operations is to avoid the dialect generator round-trip.
         """
+        if self._raw_sql is not None:
+            return self._raw_sql
         return Dialect.get_or_raise(self._dialect).generate(
             self._parsed,
             copy=True,
@@ -808,6 +874,13 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
         """
         Modify the `LIMIT` or `TOP` value of the SQL statement inplace.
         """
+        # AST mutation invalidates any cached verbatim SQL (e.g. from splice).
+        # If we already have a rewritten SQL string, re-parse it first so further
+        # AST mutations (like LIMIT injection) preserve prior text-based rewrites.
+        if self._raw_sql is not None:
+            self._parsed = self._parse_statement(self._raw_sql, self.engine)
+            self._source_sql = self._raw_sql
+            self._raw_sql = None
         if method == LimitMethod.FORCE_LIMIT:
             self._parsed.args["limit"] = exp.Limit(
                 expression=exp.Literal(this=str(limit), is_string=False)
@@ -902,7 +975,7 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
         self,
         catalog: str | None,
         schema: str | None,
-        predicates: dict[Table, list[exp.Expression]],
+        predicates: dict[Table, list[str]],
         method: RLSMethod,
     ) -> None:
         """
@@ -910,11 +983,22 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
 
         :param catalog: The default catalog for non-qualified table names
         :param schema: The default schema for non-qualified table names
+        :param predicates: Mapping of fully qualified ``Table`` to raw predicate
+            SQL strings.
         :param method: The method to use for applying the rules.
         """
         if not predicates:
             return
 
+        if method == RLSMethod.AS_PREDICATE_SPLICE:
+            self._apply_rls_splice(catalog, schema, predicates)
+            return
+
+        parsed_predicates: dict[Table, list[exp.Expression]] = {
+            table: [self.parse_predicate(predicate) for predicate in table_predicates]
+            for table, table_predicates in predicates.items()
+        }
+
         transformers = {
             RLSMethod.AS_PREDICATE: RLSAsPredicateTransformer,
             RLSMethod.AS_SUBQUERY: RLSAsSubqueryTransformer,
@@ -922,9 +1006,39 @@ class SQLStatement(BaseSQLStatement[exp.Expression]):
         if method not in transformers:
             raise ValueError(f"Invalid RLS method: {method}")
 
-        transformer = transformers[method](catalog, schema, predicates)
+        transformer = transformers[method](catalog, schema, parsed_predicates)
         self._parsed = self._parsed.transform(transformer)
 
+    def _apply_rls_splice(
+        self,
+        catalog: str | None,
+        schema: str | None,
+        predicates: dict[Table, list[str]],
+    ) -> None:
+        """
+        Apply RLS via text splicing on the original SQL.
+
+        Requires the source SQL substring to be available. Raises ``ValueError``
+        if it isn't — the caller must ensure the statement was constructed from
+        a source string (the standard ``SQLScript`` path does this).
+        """
+        from superset.sql.rls_splice import apply_rls_splice
+
+        if self._source_sql is None:
+            raise ValueError(
+                "Splice-mode RLS requires the source SQL string; "
+                "this SQLStatement was constructed without one."
+            )
+
+        spliced = apply_rls_splice(
+            self._source_sql,
+            catalog,
+            schema,
+            predicates,
+            dialect=self._dialect,
+        )
+        self._raw_sql = spliced
+
 
 class KQLSplitState(enum.Enum):
     """

superset/sql/rls_splice.py

@@ -0,0 +1,474 @@
+# 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.
+
+"""
+RLS predicate injection via text splicing.
+
+Instead of round-tripping through sqlglot's generator (which transpiles
+dialect-specific functions like ``LAST_DAY`` into something else), this approach:
+
+  1. Parses the SQL with sqlglot — only to understand structure (scope tree).
+  2. Uses sqlglot's tokenizer to get byte-accurate positions for every token
+     in the original SQL string.
+  3. For each ``SELECT`` scope that references a table with an RLS predicate,
+     finds the exact byte offset to inject at — either the end of an existing
+     ``WHERE`` clause, or just before ``GROUP BY`` / ``ORDER BY`` / ``HAVING``
+     / ``LIMIT`` / the closing paren of a subquery.
+  4. Splices the predicate text directly into the original string at that
+     offset — never calling ``.sql()``, so the generator never runs.
+
+Result: everything outside the splice points is the original SQL, byte for
+byte. Dialect-specific functions, comments, and formatting are all preserved
+exactly.
+
+Known limitations:
+  - SQL that fails to parse under the chosen dialect raises a ``ParseError``.
+    A thin dialect subclass is still required for parsing — but only for
+    parsing, not generation.
+  - Predicate strings are spliced in as raw SQL. They must come from a trusted
+    source (the RLS config), not user input.
+  - Predicate **column qualification** (prefixing bare columns with the table
+    alias) currently round-trips the predicate through the sqlglot generator
+    via ``_qualify_predicate``. Predicates that contain dialect-specific
+    functions can therefore still be transpiled by the generator at that step,
+    even though the surrounding query is preserved byte-for-byte. The
+    surrounding-query fidelity guarantee does not extend to the predicate
+    string itself.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import sqlglot
+from sqlglot import exp
+from sqlglot.optimizer.scope import traverse_scope
+from sqlglot.tokens import Token, TokenType
+
+if TYPE_CHECKING:
+    from superset.sql.parse import Table
+
+
+# Token types that end a WHERE clause / FROM section at the current paren depth,
+# indicating where a new predicate must be inserted just before.
+_CLAUSE_ENDS = {
+    TokenType.GROUP_BY,
+    TokenType.HAVING,
+    TokenType.ORDER_BY,
+    TokenType.WINDOW,
+    TokenType.QUALIFY,
+    TokenType.LIMIT,
+    TokenType.FETCH,
+    TokenType.CLUSTER_BY,
+    TokenType.DISTRIBUTE_BY,
+    TokenType.SORT_BY,
+    TokenType.CONNECT_BY,
+    TokenType.START_WITH,
+    TokenType.UNION,
+    TokenType.INTERSECT,
+    TokenType.EXCEPT,
+}
+
+_JOIN_STARTS = {
+    TokenType.JOIN,
+    TokenType.STRAIGHT_JOIN,
+    TokenType.JOIN_MARKER,
+}
+
+
+def _splice_priority(text: str) -> int:
+    """
+    Priority for applying splices at the same offset.
+
+    Insert full SQL fragments (WHERE/ON/predicates) before closing parens so
+    wrapping splices like ``pred AND (existing)`` compose correctly.
+    """
+    return 1 if text != ")" else 0
+
+
+def _after_previous_token(tokens: list[Token], index: int) -> int:
+    """
+    Return the offset immediately after the token preceding *index*.
+
+    The sqlglot tokenizer strips comments and whitespace from the token stream,
+    so the previous token's ``end + 1`` is the splice point that lands right
+    after the last real SQL content — naturally skipping any intervening
+    comments or whitespace, and never confusing ``--`` or ``/*`` inside string
+    literals for real comment delimiters.
+    """
+    if index <= 0:
+        return 0
+    return tokens[index - 1].end + 1
+
+
+def _table_from_node(
+    node: exp.Table,
+    catalog: str | None,
+    schema: str | None,
+) -> Table:
+    """
+    Build a fully qualified ``Table`` from a sqlglot ``exp.Table`` node, defaulting
+    unqualified parts to the supplied catalog/schema.
+    """
+    # Imported lazily to avoid a circular import with ``superset.sql.parse``.
+    from superset.sql.parse import Table
+
+    return Table(
+        table=node.name,
+        schema=node.db if node.db else schema,
+        catalog=node.catalog if node.catalog else catalog,
+    )
+
+
+def apply_rls_splice(
+    sql: str,
+    catalog: str | None,
+    schema: str | None,
+    predicates: dict[Table, list[str]],
+    dialect: str | None = None,
+) -> str:
+    """
+    Inject RLS predicates into ``sql`` by splicing text at the right positions.
+
+    :param sql: The original SQL query. Returned unchanged except at splice points.
+    :param catalog: The default catalog for non-qualified table names.
+    :param schema: The default schema for non-qualified table names.
+    :param predicates: Mapping of ``Table`` to predicate SQL strings. Each entry
+        maps a fully qualified table to one or more raw predicate strings to
+        ``AND`` together when that table is referenced in a SELECT scope.
+    :param dialect: The sqlglot dialect used for *parsing only* — to understand
+        scope structure and locate token positions. The generator is never
+        called, so this does not affect output formatting.
+    :return: The query with RLS predicates injected into every relevant SELECT
+        scope.
+    """
+    if not predicates or not any(predicates.values()):
+        return sql
+
+    resolved_dialect = sqlglot.Dialect.get_or_raise(dialect)
+    tokens = list(resolved_dialect.tokenize(sql))
+    tree = sqlglot.parse_one(sql, dialect=dialect)
+
+    splices: list[tuple[int, str]] = []
+    for scope in traverse_scope(tree):
+        splices.extend(
+            _splices_for_scope(
+                sql,
+                tokens,
+                scope,
+                predicates,
+                catalog,
+                schema,
+                dialect,
+            )
+        )
+
+    # Apply splices in reverse offset order so earlier positions stay valid.
+    # For equal offsets, apply predicate/WHERE/ON inserts before ")" inserts.
+    splices.sort(key=lambda item: (item[0], _splice_priority(item[1])), reverse=True)
+    result = sql
+    for offset, text in splices:
+        result = result[:offset] + text + result[offset:]
+    return result
+
+
+def _splices_for_scope(
+    sql: str,
+    tokens: list[Token],
+    scope: object,
+    predicates: dict[Table, list[str]],
+    catalog: str | None,
+    schema: str | None,
+    dialect: str | None,
+) -> list[tuple[int, str]]:
+    """
+    Compute all splices for a single SELECT scope.
+
+    This mirrors ``RLSAsPredicateTransformer`` semantics:
+      - predicates for FROM tables are applied to the SELECT WHERE clause as
+        ``pred AND (existing_where)``
+      - predicates for JOIN tables are applied to each JOIN ON clause as
+        ``pred AND (existing_on)`` (or ``ON pred`` when ON is absent)
+    """
+    from_predicates: list[str] = []
+    from_table_ends: list[int] = []
+    join_splices: list[tuple[int, str]] = []
+
+    for source in scope.sources.values():  # type: ignore[attr-defined]
+        source_type, table_end, pred_sql = _classify_source_predicate(
+            source,
+            predicates,
+            catalog,
+            schema,
+            dialect,
+        )
+        if source_type == "none" or table_end is None or pred_sql is None:
+            continue
+
+        if source_type == "from":
+            from_predicates.append(pred_sql)
+            from_table_ends.append(table_end)
+            continue
+
+        join_splice = _find_join_splice(sql, tokens, table_end, pred_sql)
+        if join_splice:
+            join_splices.extend(join_splice)
+
+    if not from_predicates:
+        return join_splices
+
+    combined_predicates = " AND ".join(dict.fromkeys(from_predicates))
+    from_splice = _find_where_splice(
+        sql,
+        tokens,
+        max(from_table_ends),
+        combined_predicates,
+    )
+    return [*join_splices, *from_splice]
+
+
+def _table_end(source: exp.Table) -> int | None:
+    ident = source.find(exp.Identifier)
+    meta = getattr(ident, "_meta", None) if ident else None
+    if meta is None:
+        return None
+    return meta.get("end")
+
+
+def _classify_source_predicate(
+    source: object,
+    predicates: dict[Table, list[str]],
+    catalog: str | None,
+    schema: str | None,
+    dialect: str | None,
+) -> tuple[str, int | None, str | None]:
+    """
+    Return source kind (from/join/none), table end offset, and predicate SQL.
+    """
+    if not isinstance(source, exp.Table):
+        return ("none", None, None)
+
+    table = _table_from_node(source, catalog, schema)
+    table_predicates = [
+        _qualify_predicate(predicate, source, dialect)
+        for predicate in predicates.get(table, [])
+        if predicate
+    ]
+    if not table_predicates:
+        return ("none", None, None)
+
+    table_end = _table_end(source)
+    if table_end is None:
+        return ("none", None, None)
+
+    pred_sql = " AND ".join(dict.fromkeys(table_predicates))
+    if isinstance(source.parent, exp.From):
+        return ("from", table_end, pred_sql)
+    if isinstance(source.parent, exp.Join):
+        return ("join", table_end, pred_sql)
+    return ("none", None, None)
+
+
+def _qualify_predicate(
+    predicate: str,
+    table_node: exp.Table,
+    dialect: str | None,
+) -> str:
+    """
+    Qualify predicate columns with the table alias/name, mirroring
+    ``RLSAsPredicateTransformer``.
+
+    Note: this re-renders the predicate via the sqlglot generator, so the
+    splice-mode fidelity guarantee does not extend to the predicate text
+    itself. Predicates containing dialect-specific functions may be transpiled
+    here even though the surrounding query is preserved byte-for-byte.
+    """
+    parsed = sqlglot.parse_one(predicate, dialect=dialect)
+    table = table_node.alias_or_name
+    table_expr = exp.to_identifier(table)
+    for column in parsed.find_all(exp.Column):
+        column.set("table", table_expr.copy())
+    return parsed.sql(dialect=dialect)
+
+
+def _scan_until_scope_boundary(
+    tokens: list[Token],
+    anchor: int,
+    *,
+    stop_at_join: bool,
+) -> tuple[str, int | None]:
+    """
+    Scan tokens forward from ``anchor`` until a clause/scope boundary.
+
+    Returns ``("where", index)`` when a WHERE token is found at depth 0,
+    ``("boundary", index)`` for a non-WHERE boundary token, and
+    ``("eof", None)`` when no boundary token is found.
+    """
+    depth = 0
+    for i, tok in enumerate(tokens):
+        if tok.start <= anchor:
+            continue
+
+        if tok.token_type == TokenType.L_PAREN:
+            depth += 1
+            continue
+
+        if tok.token_type == TokenType.R_PAREN:
+            if depth == 0:
+                return ("boundary", i)
+            depth -= 1
+            continue
+
+        if depth > 0:
+            continue
+
+        if tok.token_type == TokenType.WHERE:
+            return ("where", i)
+
+        if tok.token_type in _CLAUSE_ENDS or (
+            stop_at_join and tok.token_type in _JOIN_STARTS
+        ):
+            return ("boundary", i)
+
+    return ("eof", None)
+
+
+def _find_condition_end(
+    tokens: list[Token],
+    start_index: int,
+    *,
+    stop_at_join: bool,
+) -> int:
+    """
+    Find the end offset for a WHERE/ON condition body.
+    """
+    depth = 0
+    prev_end = tokens[start_index].end
+    for tok in tokens[start_index + 1 :]:
+        if tok.token_type == TokenType.L_PAREN:
+            depth += 1
+        elif tok.token_type == TokenType.R_PAREN:
+            if depth == 0:
+                return prev_end + 1
+            depth -= 1
+        elif depth == 0 and (
+            (stop_at_join and tok.token_type == TokenType.WHERE)
+            or tok.token_type in _CLAUSE_ENDS
+            or (stop_at_join and tok.token_type in _JOIN_STARTS)
+        ):
+            return prev_end + 1
+        prev_end = tok.end
+    return prev_end + 1
+
+
+def _find_where_splice(
+    sql: str,
+    tokens: list[Token],
+    anchor: int,
+    pred_sql: str,
+) -> list[tuple[int, str]]:
+    """
+    Build splices for adding predicate semantics to the SELECT WHERE clause:
+    ``pred`` when absent, ``pred AND (existing)`` when present.
+    """
+    kind, idx = _scan_until_scope_boundary(tokens, anchor, stop_at_join=False)
+    if kind == "where" and idx is not None:
+        if idx + 1 >= len(tokens):
+            return [(tokens[idx].end + 1, f" {pred_sql}")]
+        body_start = tokens[idx + 1].start
+        body_end = _find_condition_end(tokens, idx, stop_at_join=False)
+        return [
+            (body_start, f"{pred_sql} AND ("),
+            (body_end, ")"),
+        ]
+
+    if kind == "boundary" and idx is not None:
+        return [(_after_previous_token(tokens, idx), f" WHERE {pred_sql}")]
+
+    return [(len(sql), f" WHERE {pred_sql}")]
+
+
+def _find_join_splice(
+    sql: str,
+    tokens: list[Token],
+    anchor: int,
+    pred_sql: str,
+) -> list[tuple[int, str]]:
+    """
+    Build splices for adding predicate semantics to a JOIN clause:
+    ``ON pred`` when ON absent, ``ON pred AND (existing_on)`` when present.
+    """
+    on_index, boundary_index = _scan_join_clause(tokens, anchor)
+
+    if on_index is not None:
+        if on_index + 1 >= len(tokens):
+            return [(tokens[on_index].end + 1, f" {pred_sql}")]
+        body_start = tokens[on_index + 1].start
+        body_end = _find_condition_end(tokens, on_index, stop_at_join=True)
+        return [
+            (body_start, f"{pred_sql} AND ("),
+            (body_end, ")"),
+        ]
+
+    if boundary_index is not None:
+        return [(_after_previous_token(tokens, boundary_index), f" ON {pred_sql}")]
+
+    return [(len(sql), f" ON {pred_sql}")]
+
+
+def _scan_join_clause(
+    tokens: list[Token],
+    anchor: int,
+) -> tuple[int | None, int | None]:
+    """
+    Find ON and boundary token indexes for a JOIN segment.
+    """
+    depth = 0
+    on_index: int | None = None
+    boundary_index: int | None = None
+
+    for i, tok in enumerate(tokens):
+        if tok.start <= anchor:
+            continue
+
+        if tok.token_type == TokenType.L_PAREN:
+            depth += 1
+            continue
+
+        if tok.token_type == TokenType.R_PAREN:
+            if depth == 0:
+                boundary_index = i
+                break
+            depth -= 1
+            continue
+
+        if depth > 0:
+            continue
+
+        if tok.token_type == TokenType.ON and on_index is None:
+            on_index = i
+            continue
+
+        if tok.token_type == TokenType.WHERE:
+            boundary_index = i
+            break
+
+        if tok.token_type in _JOIN_STARTS or tok.token_type in _CLAUSE_ENDS:
+            boundary_index = i
+            break
+
+    return on_index, boundary_index

superset/utils/rls.py

@@ -40,17 +40,19 @@ def apply_rls(
 
     :returns: True if any RLS predicates were actually applied, False otherwise.
     """
-    # There are two ways to insert RLS: either replacing the table with a subquery
+    # There are three ways to insert RLS:
-    # that has the RLS, or appending the RLS to the ``WHERE`` clause. The former is
+    #   - replace the table with a subquery containing the RLS (safest, but not
-    # safer, but not supported in all databases.
+    #     supported in all databases)
-    method = database.db_engine_spec.get_rls_method()
+    #   - append the RLS to the ``WHERE`` clause via AST transformation
+    #   - splice the RLS into the original SQL string (preserves dialect-specific
+    #     syntax that the sqlglot generator would otherwise transpile)
+    method = database.db_engine_spec.rls_method
 
-    # collect all RLS predicates for all tables in the query
+    predicates: dict[Table, list[str]] = {}
-    predicates: dict[Table, list[Any]] = {}
     for table in parsed_statement.tables:
         table = table.qualify(catalog=catalog, schema=schema)
-        predicates[table] = [
+        raw_predicates = [
-            parsed_statement.parse_predicate(predicate)
+            predicate
             for predicate in get_predicates_for_table(
                 table,
                 database,
@@ -58,6 +60,7 @@ def apply_rls(
             )
             if predicate
         ]
+        predicates[table] = raw_predicates
 
     has_predicates = any(predicates.values())
     parsed_statement.apply_rls(catalog, schema, predicates, method)

tests/unit_tests/db_engine_specs/test_base.py

@@ -36,7 +36,7 @@ from sqlalchemy.sql import sqltypes
 from superset.db_engine_specs.base import BaseEngineSpec, convert_inspector_columns
 from superset.errors import ErrorLevel, SupersetError, SupersetErrorType
 from superset.exceptions import OAuth2RedirectError
-from superset.sql.parse import Table
+from superset.sql.parse import RLSMethod, Table
 from superset.superset_typing import (
     OAuth2ClientConfig,
     OAuth2State,
@@ -1283,3 +1283,8 @@ def test_start_oauth2_dance_falls_back_to_url_for(mocker: MockerFixture) -> None
     error = exc_info.value.error
 
     assert error.extra["redirect_uri"] == fallback_uri
+
+
+def test_default_rls_method_is_subquery() -> None:
+    """Base engine spec defaults to subquery-based RLS."""
+    assert BaseEngineSpec.rls_method == RLSMethod.AS_SUBQUERY

tests/unit_tests/models/test_virtual_dataset_format.py

@@ -209,7 +209,7 @@ class TestApplyRlsReturnValue:
         from superset.utils.rls import apply_rls
 
         database = MagicMock()
-        database.db_engine_spec.get_rls_method.return_value = MagicMock()
+        database.db_engine_spec.rls_method = RLSMethod.AS_SUBQUERY
         database.get_default_catalog.return_value = None
 
         statement = MagicMock()
@@ -237,7 +237,7 @@ class TestApplyRlsReturnValue:
         mock_get_predicates.return_value = []
 
         database = MagicMock()
-        database.db_engine_spec.get_rls_method.return_value = MagicMock()
+        database.db_engine_spec.rls_method = RLSMethod.AS_SUBQUERY
         database.get_default_catalog.return_value = None
 
         mock_table = MagicMock()
@@ -268,7 +268,7 @@ class TestApplyRlsReturnValue:
         mock_get_predicates.return_value = ["user_id = 42"]
 
         database = MagicMock()
-        database.db_engine_spec.get_rls_method.return_value = MagicMock()
+        database.db_engine_spec.rls_method = RLSMethod.AS_SUBQUERY
         database.get_default_catalog.return_value = None
 
         mock_table = MagicMock()
@@ -276,8 +276,6 @@ class TestApplyRlsReturnValue:
 
         statement = MagicMock()
         statement.tables = [mock_table]
-        statement.parse_predicate.return_value = MagicMock()
-
         result = apply_rls(
             database=database,
             catalog=None,
@@ -312,11 +310,10 @@ class TestRLSSubqueryAlias:
         """
         sql = "SELECT pens.pen_id, pens.is_green FROM public.pens"
         statement = SQLStatement(sql, engine="redshift")
-        predicate = statement.parse_predicate("user_id = 1")
         statement.apply_rls(
             None,
             "public",
-            {Table("pens", "public", None): [predicate]},
+            {Table("pens", "public", None): ["user_id = 1"]},
             RLSMethod.AS_SUBQUERY,
         )
         result = statement.format()
@@ -333,11 +330,10 @@ class TestRLSSubqueryAlias:
         """
         sql = "SELECT pens.pen_id, pens.is_green FROM mycat.public.pens"
         statement = SQLStatement(sql, engine="redshift")
-        predicate = statement.parse_predicate("user_id = 1")
         statement.apply_rls(
             None,
             "public",
-            {Table("pens", "public", "mycat"): [predicate]},
+            {Table("pens", "public", "mycat"): ["user_id = 1"]},
             RLSMethod.AS_SUBQUERY,
         )
         result = statement.format()
@@ -351,11 +347,10 @@ class TestRLSSubqueryAlias:
         """
         sql = "SELECT p.pen_id, p.is_green FROM public.pens p"
         statement = SQLStatement(sql, engine="redshift")
-        predicate = statement.parse_predicate("user_id = 1")
         statement.apply_rls(
             None,
             "public",
-            {Table("pens", "public", None): [predicate]},
+            {Table("pens", "public", None): ["user_id = 1"]},
             RLSMethod.AS_SUBQUERY,
         )
         result = statement.format()
@@ -369,11 +364,10 @@ class TestRLSSubqueryAlias:
         """
         sql = "SELECT pen_id, is_green FROM public.pens"
         statement = SQLStatement(sql, engine="redshift")
-        predicate = statement.parse_predicate("user_id = 1")
         statement.apply_rls(
             None,
             "public",
-            {Table("pens", "public", None): [predicate]},
+            {Table("pens", "public", None): ["user_id = 1"]},
             RLSMethod.AS_SUBQUERY,
         )
         result = statement.format()

tests/unit_tests/sql/parse_tests.py

@@ -1704,6 +1704,21 @@ def test_set_limit_value(
     assert statement.format() == expected
 
 
+def test_set_limit_value_after_splice_reparses_from_raw_sql() -> None:
+    """
+    When a statement has cached verbatim SQL from splice-mode rewrites, setting
+    limit should reparse that SQL before mutating the AST.
+    """
+    statement = SQLStatement("SELECT * FROM some_table", "postgresql")
+    statement._raw_sql = "SELECT * FROM some_table WHERE tenant_id = 42"
+
+    statement.set_limit_value(10, LimitMethod.FORCE_LIMIT)
+    formatted = statement.format()
+
+    assert "tenant_id = 42" in formatted
+    assert "LIMIT 10" in formatted
+
+
 @pytest.mark.parametrize(
     "kql, limit, expected",
     [
@@ -2198,7 +2213,7 @@ def test_rls_subquery_transformer(
     statement.apply_rls(
         "catalog1",
         "schema1",
-        {k: [parse_one(v)] for k, v in rules.items()},
+        {k: [v] for k, v in rules.items()},
         RLSMethod.AS_SUBQUERY,
     )
     assert statement.format() == expected
@@ -2542,12 +2557,337 @@ def test_rls_predicate_transformer(
     statement.apply_rls(
         "catalog1",
         "schema1",
-        {k: [parse_one(v)] for k, v in rules.items()},
+        {k: [v] for k, v in rules.items()},
         RLSMethod.AS_PREDICATE,
     )
     assert statement.format() == expected
 
 
+@pytest.mark.parametrize(
+    "sql, rules, expected",
+    [
+        (
+            "SELECT t.foo FROM some_table AS t",
+            {Table("some_table", "schema1", "catalog1"): "t.id = 42"},
+            "SELECT t.foo FROM some_table AS t WHERE t.id = 42",
+        ),
+        (
+            "SELECT t.foo FROM some_table AS t WHERE bar = 'baz' OR foo = 'qux'",
+            {Table("some_table", "schema1", "catalog1"): "t.id = 42"},
+            "SELECT t.foo FROM some_table AS t WHERE t.id = 42 "
+            "AND (bar = 'baz' OR foo = 'qux')",
+        ),
+        (
+            "SELECT * FROM table JOIN other_table ON table.id = other_table.id",
+            {Table("other_table", "schema1", "catalog1"): "other_table.id = 42"},
+            "SELECT * FROM table JOIN other_table ON other_table.id = 42 "
+            "AND (table.id = other_table.id)",
+        ),
+        (
+            "SELECT * FROM table JOIN other_table",
+            {Table("other_table", "schema1", "catalog1"): "other_table.id = 42"},
+            "SELECT * FROM table JOIN other_table ON other_table.id = 42",
+        ),
+        (
+            "SELECT * FROM table JOIN other_table ON table.id = other_table.id "
+            "WHERE 1=1",
+            {Table("other_table", "schema1", "catalog1"): "other_table.id = 42"},
+            "SELECT * FROM table JOIN other_table ON other_table.id = 42 "
+            "AND (table.id = other_table.id) WHERE 1=1",
+        ),
+    ],
+)
+def test_rls_predicate_splice_semantics_match_predicate(
+    sql: str,
+    rules: dict[Table, str],
+    expected: str,
+) -> None:
+    """
+    Splice mode should preserve predicate-mode semantics for boolean grouping
+    and JOIN-vs-WHERE placement.
+    """
+    statement = SQLStatement(sql)
+    statement.apply_rls(
+        "catalog1",
+        "schema1",
+        {k: [v] for k, v in rules.items()},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == expected
+
+
+@pytest.mark.parametrize(
+    "sql, rules, expected",
+    [
+        # Simple — no WHERE clause to extend.
+        (
+            "SELECT LAST_DAY(d) FROM some_table",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT LAST_DAY(d) FROM some_table WHERE some_table.tenant_id = 42",
+        ),
+        # Append to an existing WHERE clause.
+        (
+            "SELECT LAST_DAY(d) FROM some_table WHERE status = 'open'",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT LAST_DAY(d) FROM some_table "
+            "WHERE some_table.tenant_id = 42 AND (status = 'open')",
+        ),
+        # WHERE precedes GROUP BY: predicate goes before GROUP BY.
+        (
+            "SELECT LAST_DAY(d) FROM some_table WHERE status = 'open' GROUP BY d",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT LAST_DAY(d) FROM some_table "
+            "WHERE some_table.tenant_id = 42 AND (status = 'open') GROUP BY d",
+        ),
+        # No WHERE, but GROUP BY and ORDER BY are present.
+        (
+            "SELECT LAST_DAY(d) FROM some_table GROUP BY d ORDER BY d",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT LAST_DAY(d) FROM some_table WHERE some_table.tenant_id = 42 "
+            "GROUP BY d ORDER BY d",
+        ),
+        # JOIN — predicate scoped to one of the tables.
+        (
+            "SELECT o.id FROM some_table o JOIN locations l ON o.loc_id = l.id",
+            {Table("some_table", "schema1", "catalog1"): "o.tenant_id = 42"},
+            "SELECT o.id FROM some_table o JOIN locations l "
+            "ON o.loc_id = l.id WHERE o.tenant_id = 42",
+        ),
+        # JOIN — different predicate per table, both spliced into one WHERE.
+        (
+            "SELECT * FROM some_table JOIN events ON some_table.id = events.order_id",
+            {
+                Table("events", "schema1", "catalog1"): "events.user_id = 99",
+                Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42",
+            },
+            "SELECT * FROM some_table JOIN events "
+            "ON events.user_id = 99 AND (some_table.id = events.order_id) "
+            "WHERE some_table.tenant_id = 42",
+        ),
+        # Subquery in FROM — splice into the inner SELECT.
+        (
+            "SELECT x FROM (SELECT LAST_DAY(d) AS x FROM some_table) sub",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT x FROM (SELECT LAST_DAY(d) AS x FROM some_table "
+            "WHERE some_table.tenant_id = 42) sub",
+        ),
+        # CTE — splice into the CTE body.
+        (
+            "WITH cte AS (SELECT LAST_DAY(d) FROM some_table) SELECT * FROM cte",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "WITH cte AS (SELECT LAST_DAY(d) FROM some_table "
+            "WHERE some_table.tenant_id = 42) SELECT * FROM cte",
+        ),
+        # Dialect-specific function (LAST_DAY) preserved verbatim.
+        (
+            "SELECT id, LAST_DAY(created_at) FROM some_table WHERE region = 'US'",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT id, LAST_DAY(created_at) FROM some_table "
+            "WHERE some_table.tenant_id = 42 AND (region = 'US')",
+        ),
+        # Multiline + inline comment preserved exactly.
+        (
+            "SELECT LAST_DAY(created_at) -- last day of month\n"
+            "FROM some_table\n"
+            "WHERE region = 'US'",
+            {Table("some_table", "schema1", "catalog1"): "some_table.tenant_id = 42"},
+            "SELECT LAST_DAY(created_at) -- last day of month\n"
+            "FROM some_table\n"
+            "WHERE some_table.tenant_id = 42 AND (region = 'US')",
+        ),
+        # Schema-qualified table name (no default schema match) — no predicate.
+        (
+            "SELECT t.foo FROM schema2.some_table AS t",
+            {Table("some_table", "schema1", "catalog1"): "t.id = 42"},
+            "SELECT t.foo FROM schema2.some_table AS t",
+        ),
+    ],
+)
+def test_rls_predicate_splice(
+    sql: str,
+    rules: dict[Table, str],
+    expected: str,
+) -> None:
+    """
+    Test the splice-mode RLS via ``RLSMethod.AS_PREDICATE_SPLICE``.
+
+    Splice mode rewrites the original SQL string instead of re-rendering the
+    AST through the dialect generator, so byte-level fidelity (including
+    dialect-specific functions, comments, and whitespace) is preserved.
+    """
+    statement = SQLStatement(sql)
+    statement.apply_rls(
+        "catalog1",
+        "schema1",
+        {k: [v] for k, v in rules.items()},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == expected
+
+
+def test_rls_predicate_splice_requires_source() -> None:
+    """
+    Splice mode requires the original SQL substring; constructing a statement
+    purely from an AST should make splice mode raise.
+    """
+    ast = parse_one("SELECT * FROM some_table")
+    statement = SQLStatement(ast=ast, engine="postgresql")
+    with pytest.raises(ValueError, match="Splice-mode RLS requires the source SQL"):
+        statement.apply_rls(
+            "catalog1",
+            "schema1",
+            {Table("some_table", "schema1", "catalog1"): ["id = 42"]},
+            RLSMethod.AS_PREDICATE_SPLICE,
+        )
+
+
+def test_rls_predicate_splice_preserves_dialect_function() -> None:
+    """
+    Splice mode must NOT round-trip through the sqlglot generator. ``LAST_DAY``
+    on the postgres dialect would otherwise be transpiled by the generator.
+    """
+    sql = "SELECT LAST_DAY(d) FROM some_table"
+    statement = SQLStatement(sql, engine="postgresql")
+    statement.apply_rls(
+        None,
+        None,
+        {Table("some_table"): ["some_table.tenant_id = 42"]},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == (
+        "SELECT LAST_DAY(d) FROM some_table WHERE some_table.tenant_id = 42"
+    )
+
+
+def test_rls_predicate_splice_combines_multiple_predicates() -> None:
+    """
+    Splice mode should AND together multiple predicates configured for the same
+    table into a single injected condition.
+    """
+    sql = "SELECT * FROM some_table WHERE status = 'open'"
+    statement = SQLStatement(sql, engine="postgresql")
+    statement.apply_rls(
+        None,
+        None,
+        {
+            Table("some_table"): [
+                "some_table.tenant_id = 42",
+                "some_table.region = 'US'",
+            ],
+        },
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == (
+        "SELECT * FROM some_table "
+        "WHERE some_table.tenant_id = 42 AND some_table.region = 'US' "
+        "AND (status = 'open')"
+    )
+
+
+def test_rls_predicate_splice_string_predicates_skip_parse() -> None:
+    """
+    Splice mode accepts predicate strings directly — no ``parse_predicate`` is
+    needed at the call site.
+    """
+    sql = "SELECT * FROM some_table"
+    statement = SQLStatement(sql, engine="postgresql")
+    statement.apply_rls(
+        None,
+        None,
+        {Table("some_table"): ["some_table.tenant_id = 42 AND some_table.active"]},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == (
+        "SELECT * FROM some_table WHERE some_table.tenant_id = 42 AND some_table.active"
+    )
+
+
+@pytest.mark.parametrize(
+    "sql, expected",
+    [
+        (
+            "SELECT * FROM some_table -- hi\nGROUP BY id",
+            "SELECT * FROM some_table WHERE some_table.tenant_id = 42 "
+            "-- hi\nGROUP BY id",
+        ),
+        (
+            "SELECT * FROM some_table /* inline */ GROUP BY id",
+            "SELECT * FROM some_table WHERE some_table.tenant_id = 42 "
+            "/* inline */ GROUP BY id",
+        ),
+    ],
+)
+def test_rls_predicate_splice_inserts_before_comments(sql: str, expected: str) -> None:
+    """
+    Splice mode should insert predicates before comments that precede the next
+    clause boundary, so comments do not swallow the injected SQL.
+    """
+    statement = SQLStatement(sql, engine="postgresql")
+    statement.apply_rls(
+        None,
+        None,
+        {Table("some_table"): ["some_table.tenant_id = 42"]},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == expected
+
+
+@pytest.mark.parametrize(
+    "sql, engine, expected",
+    [
+        (
+            "SELECT * FROM some_table QUALIFY row_number() OVER "
+            "(PARTITION BY id ORDER BY ts DESC) = 1",
+            "snowflake",
+            "SELECT * FROM some_table WHERE some_table.tenant_id = 42 "
+            "QUALIFY row_number() OVER (PARTITION BY id ORDER BY ts DESC) = 1",
+        ),
+        (
+            "SELECT sum(v) OVER () FROM some_table WINDOW w AS (PARTITION BY id)",
+            "postgresql",
+            "SELECT sum(v) OVER () FROM some_table "
+            "WHERE some_table.tenant_id = 42 "
+            "WINDOW w AS (PARTITION BY id)",
+        ),
+    ],
+)
+def test_rls_predicate_splice_handles_additional_clause_boundaries(
+    sql: str,
+    engine: str,
+    expected: str,
+) -> None:
+    """
+    Splice mode should insert WHERE before clause types that can legally follow
+    FROM/WHERE (for example QUALIFY and WINDOW).
+    """
+    statement = SQLStatement(sql, engine=engine)
+    statement.apply_rls(
+        None,
+        None,
+        {Table("some_table"): ["some_table.tenant_id = 42"]},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    assert statement.format() == expected
+
+
+def test_rls_predicate_splice_then_limit_keeps_rls() -> None:
+    """
+    LIMIT rewrites after splice-mode RLS should retain injected predicates.
+    """
+    statement = SQLStatement("SELECT * FROM some_table", engine="postgresql")
+    statement.apply_rls(
+        None,
+        None,
+        {Table("some_table"): ["tenant_id = 42"]},
+        RLSMethod.AS_PREDICATE_SPLICE,
+    )
+    statement.set_limit_value(101, LimitMethod.FORCE_LIMIT)
+
+    formatted = statement.format()
+    assert "some_table.tenant_id = 42" in formatted
+    assert "LIMIT 101" in formatted
+
+
 @pytest.mark.parametrize(
     "sql, table, expected",
     [

tests/unit_tests/sql/rls_splice_unit_tests.py

@@ -0,0 +1,298 @@
+# 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.
+
+import pytest
+import sqlglot
+from sqlglot import Dialect, exp
+
+from superset.sql.parse import SQLStatement, Table
+from superset.sql.rls_splice import (
+    _after_previous_token,
+    _classify_source_predicate,
+    _find_condition_end,
+    _find_join_splice,
+    _find_where_splice,
+    _scan_join_clause,
+    _scan_until_scope_boundary,
+    _splices_for_scope,
+    _table_end,
+    apply_rls_splice,
+)
+
+
+def _tokenize(sql: str) -> list[sqlglot.tokens.Token]:
+    return list(Dialect.get_or_raise(None).tokenize(sql))
+
+
+def _token_index(tokens: list[sqlglot.tokens.Token], token_type: object) -> int:
+    return next(i for i, token in enumerate(tokens) if token.token_type == token_type)
+
+
+def _token_by_text(
+    tokens: list[sqlglot.tokens.Token], text: str
+) -> sqlglot.tokens.Token:
+    return next(token for token in tokens if token.text == text)
+
+
+def test_split_source_returns_none_result_when_tokenize_fails(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    class _BrokenDialect:
+        @staticmethod
+        def tokenize(_: str) -> list[sqlglot.tokens.Token]:
+            raise sqlglot.errors.SqlglotError("boom")
+
+    monkeypatch.setattr(
+        "superset.sql.parse.Dialect.get_or_raise",
+        lambda _: _BrokenDialect(),
+    )
+    assert SQLStatement._split_source("SELECT 1", "postgresql", 2) == [None, None]
+
+
+def test_apply_rls_splice_ignores_empty_predicates() -> None:
+    sql = "SELECT 1"
+    assert apply_rls_splice(sql, None, None, {Table("foo"): []}) == sql
+
+
+def test_apply_rls_splice_ignores_dash_dash_inside_string_literal() -> None:
+    """
+    Regression: the splice point must not be confused by ``--`` appearing
+    inside a string literal. Earlier ``rfind("--", ...)`` logic mistook this
+    for an inline comment and inserted the predicate inside the quoted text.
+    """
+    sql = "SELECT * FROM some_table WHERE note = '--x' GROUP BY id"
+    spliced = apply_rls_splice(
+        sql,
+        None,
+        None,
+        {Table("some_table"): ["some_table.tenant_id = 42"]},
+        dialect="postgres",
+    )
+    assert spliced == (
+        "SELECT * FROM some_table WHERE some_table.tenant_id = 42 "
+        "AND (note = '--x') GROUP BY id"
+    )
+
+
+def test_table_end_returns_none_without_metadata() -> None:
+    source = exp.Table(this=exp.Identifier(this="foo"))
+    assert _table_end(source) is None
+
+
+def test_classify_source_predicate_returns_none_without_table_metadata() -> None:
+    source = exp.Table(this=exp.Identifier(this="foo"))
+    exp.From(this=source)
+    result = _classify_source_predicate(
+        source,
+        {Table("foo"): ["id = 1"]},
+        None,
+        None,
+        None,
+    )
+    assert result == ("none", None, None)
+
+
+def test_classify_source_predicate_returns_none_for_unsupported_parent() -> None:
+    source = exp.Table(this=exp.Identifier(this="foo"))
+    source.this.meta["end"] = 3
+    exp.Alias(this=source, alias=exp.Identifier(this="alias"))
+    result = _classify_source_predicate(
+        source,
+        {Table("foo"): ["id = 1"]},
+        None,
+        None,
+        None,
+    )
+    assert result == ("none", None, None)
+
+
+def test_after_previous_token_returns_zero_at_stream_start() -> None:
+    tokens = _tokenize("SELECT 1")
+    assert _after_previous_token(tokens, 0) == 0
+
+
+def test_scan_until_scope_boundary_tracks_parenthesis_depth() -> None:
+    sql = "SELECT * FROM t WHERE (a = 1)"
+    tokens = _tokenize(sql)
+    where_token = _token_by_text(tokens, "WHERE")
+    assert _scan_until_scope_boundary(
+        tokens, where_token.start, stop_at_join=False
+    ) == (
+        "eof",
+        None,
+    )
+
+
+def test_find_condition_end_handles_subquery_closing_paren() -> None:
+    sql = "SELECT * FROM (SELECT * FROM t WHERE a = 1)"
+    tokens = _tokenize(sql)
+    where_index = _token_index(tokens, sqlglot.tokens.TokenType.WHERE)
+    end = _find_condition_end(tokens, where_index, stop_at_join=False)
+    assert sql[end] == ")"
+
+
+def test_find_condition_end_handles_parenthesized_expression() -> None:
+    sql = "SELECT * FROM t WHERE (a = 1)"
+    tokens = _tokenize(sql)
+    where_index = _token_index(tokens, sqlglot.tokens.TokenType.WHERE)
+    end = _find_condition_end(tokens, where_index, stop_at_join=False)
+    assert end == len(sql)
+
+
+def test_find_where_splice_handles_trailing_where_keyword() -> None:
+    sql = "SELECT * FROM t WHERE"
+    tokens = _tokenize(sql)
+    splices = _find_where_splice(sql, tokens, anchor=0, pred_sql="t.id = 1")
+    assert splices == [(len(sql), " t.id = 1")]
+
+
+def test_find_join_splice_handles_trailing_on_keyword() -> None:
+    sql = "SELECT * FROM a JOIN b ON"
+    tokens = _tokenize(sql)
+    b_token = _token_by_text(tokens, "b")
+    splices = _find_join_splice(sql, tokens, b_token.end, "b.id = 1")
+    assert splices == [(len(sql), " b.id = 1")]
+
+
+def test_find_join_splice_inserts_on_before_where_boundary() -> None:
+    sql = "SELECT * FROM a JOIN b WHERE x = 1"
+    tokens = _tokenize(sql)
+    b_token = _token_by_text(tokens, "b")
+    splices = _find_join_splice(sql, tokens, b_token.end, "b.id = 1")
+    assert splices == [(sql.index("WHERE") - 1, " ON b.id = 1")]
+
+
+def test_scan_join_clause_covers_nested_parentheses_and_join_boundary() -> None:
+    sql = "SELECT * FROM a JOIN b ON (a.id = b.id) JOIN c ON 1 = 1"
+    tokens = _tokenize(sql)
+    b_token = _token_by_text(tokens, "b")
+    on_index, boundary_index = _scan_join_clause(tokens, b_token.end)
+    assert on_index is not None
+    assert boundary_index is not None
+    assert tokens[boundary_index].token_type == sqlglot.tokens.TokenType.JOIN
+
+
+def test_scan_join_clause_stops_at_outer_closing_paren() -> None:
+    sql = "SELECT * FROM (SELECT * FROM a JOIN b) sub"
+    tokens = _tokenize(sql)
+    b_token = _token_by_text(tokens, "b")
+    _, boundary_index = _scan_join_clause(tokens, b_token.end)
+    assert boundary_index is not None
+    assert tokens[boundary_index].token_type == sqlglot.tokens.TokenType.R_PAREN
+
+
+def test_splices_for_scope_handles_empty_join_splice_result(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    class _Scope:
+        sources = {"x": object()}
+
+    sql = "SELECT 1"
+    tokens = _tokenize(sql)
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._classify_source_predicate",
+        lambda *args, **kwargs: ("join", 0, "x.id = 1"),
+    )
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._find_join_splice",
+        lambda *args, **kwargs: [],
+    )
+    assert (
+        _splices_for_scope(
+            sql,
+            tokens,
+            _Scope(),
+            {Table("x"): ["x.id = 1"]},
+            None,
+            None,
+            None,
+        )
+        == []
+    )
+
+
+def test_splices_for_scope_combines_join_and_from_splices(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    class _Scope:
+        sources = {"f": object(), "j": object()}
+
+    sql = "SELECT 1"
+    tokens = _tokenize(sql)
+    calls = [("from", 3, "f.id = 1"), ("join", 6, "j.id = 2")]
+
+    def _fake_classify(*args: object, **kwargs: object) -> tuple[str, int, str]:
+        return calls.pop(0)
+
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._classify_source_predicate", _fake_classify
+    )
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._find_join_splice",
+        lambda *args, **kwargs: [(50, " ON j.id = 2")],
+    )
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._find_where_splice",
+        lambda *args, **kwargs: [(20, " WHERE f.id = 1")],
+    )
+
+    assert _splices_for_scope(
+        sql,
+        tokens,
+        _Scope(),
+        {Table("f"): ["id = 1"], Table("j"): ["id = 2"]},
+        None,
+        None,
+        None,
+    ) == [(50, " ON j.id = 2"), (20, " WHERE f.id = 1")]
+
+
+def test_splices_for_scope_join_then_next_source(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    class _Scope:
+        sources = {"j": object(), "f": object()}
+
+    sql = "SELECT 1"
+    tokens = _tokenize(sql)
+    calls = [("join", 3, "j.id = 2"), ("none", None, None)]
+
+    def _fake_classify(
+        *args: object, **kwargs: object
+    ) -> tuple[str, int | None, str | None]:
+        return calls.pop(0)
+
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._classify_source_predicate", _fake_classify
+    )
+    monkeypatch.setattr(
+        "superset.sql.rls_splice._find_join_splice",
+        lambda *args, **kwargs: [],
+    )
+
+    assert (
+        _splices_for_scope(
+            sql,
+            tokens,
+            _Scope(),
+            {Table("j"): ["id = 2"]},
+            None,
+            None,
+            None,
+        )
+        == []
+    )