feat(postgres): add SQL/XML standard expressions

changelog.d/41.added.md

@@ -0,0 +1 @@
+Added PostgreSQL support for core SQL/XML standard expressions, including XML construction, serialization, aggregation, and query/table expression capability declarations.

src/rhosocial/activerecord/backend/impl/postgres/dialect.py

@@ -14,6 +14,7 @@
 
 from rhosocial.activerecord.backend.dialect.base import SQLDialectBase
 from rhosocial.activerecord.backend.dialect.mixins import (
+    SQLXMLMixin,
     CollationMixin,
     CTEMixin,
     FilterClauseMixin,
@@ -43,6 +44,12 @@
     ConstraintMixin,
 )
 from rhosocial.activerecord.backend.dialect.protocols import (
+    SQLXMLSupport,
+    SQLXMLParsingSupport,
+    SQLXMLSerializationSupport,
+    SQLXMLConstructionSupport,
+    SQLXMLAggregationSupport,
+    SQLXMLQueryingSupport,
     CollationSupport,
     CTESupport,
     FilterClauseSupport,
@@ -226,6 +233,7 @@
 
 class PostgresDialect(
     SQLDialectBase,
+    SQLXMLMixin,
     CollationMixin,
     SetOperationMixin,
     TruncateMixin,
@@ -316,6 +324,12 @@ class PostgresDialect(
     PostgresStoredProcedureMixin,
     PostgresAdvisoryLockMixin,
     # Protocol supports
+    SQLXMLSupport,
+    SQLXMLParsingSupport,
+    SQLXMLSerializationSupport,
+    SQLXMLConstructionSupport,
+    SQLXMLAggregationSupport,
+    SQLXMLQueryingSupport,
     CollationSupport,
     SetOperationSupport,
     TruncateSupport,
@@ -471,6 +485,58 @@ def get_server_version(self) -> Tuple[int, int, int]:
         """Return the PostgreSQL version this dialect is configured for."""
         return self.version
 
+    def supports_xmlparse(self) -> bool:
+        """XMLPARSE is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlserialize(self) -> bool:
+        """XMLSERIALIZE is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlelement(self) -> bool:
+        """XMLELEMENT is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlattributes(self) -> bool:
+        """XMLATTRIBUTES is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlforest(self) -> bool:
+        """XMLFOREST is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlconcat(self) -> bool:
+        """XMLCONCAT is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlcomment(self) -> bool:
+        """XMLCOMMENT is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlpi(self) -> bool:
+        """XMLPI is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlroot(self) -> bool:
+        """XMLROOT is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlagg(self) -> bool:
+        """XMLAGG is supported since PostgreSQL 8.3."""
+        return self.version >= (8, 3, 0)
+
+    def supports_xmlquery(self) -> bool:
+        """PostgreSQL does not implement standard SQL/XML XMLQUERY."""
+        return False
+
+    def supports_xmlexists(self) -> bool:
+        """XMLEXISTS is supported since PostgreSQL 8.4."""
+        return self.version >= (8, 4, 0)
+
+    def supports_xmltable(self) -> bool:
+        """XMLTABLE is supported since PostgreSQL 10."""
+        return self.version >= (10, 0, 0)
+
     def supports_collate_expression(self) -> bool:
         """PostgreSQL supports expression-level COLLATE."""
         return True
@@ -1637,9 +1703,25 @@ def supports_functions(self) -> Dict[str, "FunctionSupportInfo"]:
         )
         from rhosocial.activerecord.backend.impl.postgres import functions as postgres_functions
 
+        expression_constructors = {
+            "xmlagg",
+            "xmlattributes",
+            "xmlcomment",
+            "xmlconcat",
+            "xmlelement",
+            "xmlexists",
+            "xmlforest",
+            "xmlparse",
+            "xmlpi",
+            "xmlquery",
+            "xmlroot",
+            "xmlserialize",
+            "xmltable",
+        }
         result: Dict[str, FunctionSupportInfo] = {}
         for func_name in core_functions:
-            result[func_name] = self._check_function_support(func_name)
+            if func_name not in expression_constructors:
+                result[func_name] = self._check_function_support(func_name)
 
         postgres_funcs = getattr(postgres_functions, "__all__", [])
         for func_name in postgres_funcs:

src/rhosocial/activerecord/backend/impl/postgres/examples/sqlxml/__init__.py

@@ -0,0 +1 @@
+"""SQL/XML expression examples for PostgreSQL."""

src/rhosocial/activerecord/backend/impl/postgres/examples/sqlxml/item_1.xml

@@ -0,0 +1 @@
+<item id="1">alpha</item>

src/rhosocial/activerecord/backend/impl/postgres/examples/sqlxml/item_2.xml

@@ -0,0 +1 @@
+<item id="2">beta</item>

src/rhosocial/activerecord/backend/impl/postgres/examples/sqlxml/root.xml

@@ -0,0 +1,4 @@
+<root>
+  <item id="1">alpha</item>
+  <item id="2">beta</item>
+</root>