Accept TEXT and CDATA nodes in XMLTABLE's column_expression.

Column expressions that match TEXT or CDATA nodes must return the
contents of the nodes themselves, not the content of non-existing
children (i.e. the empty string).

Author: Markus Winand
Reported-by: Markus Winand
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/0684A598-002C-42A2-AE12-F024A324EAE4@winand.at

4 files changed, 28 insertions, 24 deletions

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index 7cdb87ef85b..8307f1cf47b 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -4508,11 +4508,21 @@ XmlTableGetValue(TableFuncScanState *state, int colnum,
 			else if (count == 1)
 			{
 				xmlChar    *str;
+				xmlNodePtr	node;
 
-				str = xmlNodeListGetString(xtCxt->doc,
-										   xpathobj->nodesetval->nodeTab[0]->xmlChildrenNode,
-										   1);
+				/*
+				 * Most nodes (elements and even attributes) store their data
+				 * in children nodes. If they don't have children nodes, it
+				 * means that they are empty (e.g. <element/>). Text nodes and
+				 * CDATA sections are an exception: they don't have children
+				 * but have content in the Text/CDATA node itself.
+				 */
+				node = xpathobj->nodesetval->nodeTab[0];
+				if (node->type != XML_CDATA_SECTION_NODE &&
+					node->type != XML_TEXT_NODE)
+					node = node->xmlChildrenNode;
 
+				str = xmlNodeListGetString(xtCxt->doc, node, 1);
 				if (str != NULL)
 				{
 					PG_TRY();
@@ -4529,13 +4539,7 @@ XmlTableGetValue(TableFuncScanState *state, int colnum,
 				}
 				else
 				{
-					/*
-					 * This line ensure mapping of empty tags to PostgreSQL
-					 * value. Usually we would to map a empty tag to empty
-					 * string. But this mapping can create empty string when
-					 * user doesn't expect it - when empty tag is enforced by
-					 * libxml2 - when user uses a text() function for example.
-					 */
+					/* Ensure mapping of empty tags to PostgreSQL values. */
 					cstr = "";
 				}
 			}
diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index 7fa13091087..3eb638ca258 100644
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -1024,7 +1024,7 @@ SELECT  xmltable.*
                          PASSING data
                          COLUMNS id int PATH '@id',
                                   _id FOR ORDINALITY,
-                                  country_name text PATH 'COUNTRY_NAME' NOT NULL,
+                                  country_name text PATH 'COUNTRY_NAME/text()' NOT NULL,
                                   country_id text PATH 'COUNTRY_ID',
                                   region_id int PATH 'REGION_ID',
                                   size float PATH 'SIZE',
@@ -1046,7 +1046,7 @@ CREATE VIEW xmltableview1 AS SELECT  xmltable.*
                          PASSING data
                          COLUMNS id int PATH '@id',
                                   _id FOR ORDINALITY,
-                                  country_name text PATH 'COUNTRY_NAME' NOT NULL,
+                                  country_name text PATH 'COUNTRY_NAME/text()' NOT NULL,
                                   country_id text PATH 'COUNTRY_ID',
                                   region_id int PATH 'REGION_ID',
                                   size float PATH 'SIZE',
@@ -1075,7 +1075,7 @@ CREATE OR REPLACE VIEW public.xmltableview1 AS
     "xmltable".premier_name
    FROM ( SELECT xmldata.data
            FROM xmldata) x,
-    LATERAL XMLTABLE(('/ROWS/ROW'::text) PASSING (x.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
+    LATERAL XMLTABLE(('/ROWS/ROW'::text) PASSING (x.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME/text()'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
 EXPLAIN (COSTS OFF) SELECT * FROM xmltableview1;
                QUERY PLAN                
 -----------------------------------------
@@ -1085,15 +1085,15 @@ EXPLAIN (COSTS OFF) SELECT * FROM xmltableview1;
 (3 rows)
 
 EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
-                                                                                                                                                                                                                        QUERY PLAN                                                                                                                                                                                                                         
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+                                                                                                                                                                                                                            QUERY PLAN                                                                                                                                                                                                                            
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Nested Loop
    Output: "xmltable".id, "xmltable"._id, "xmltable".country_name, "xmltable".country_id, "xmltable".region_id, "xmltable".size, "xmltable".unit, "xmltable".premier_name
    ->  Seq Scan on public.xmldata
          Output: xmldata.data
    ->  Table Function Scan on "xmltable"
          Output: "xmltable".id, "xmltable"._id, "xmltable".country_name, "xmltable".country_id, "xmltable".region_id, "xmltable".size, "xmltable".unit, "xmltable".premier_name
-         Table Function Call: XMLTABLE(('/ROWS/ROW'::text) PASSING (xmldata.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
+         Table Function Call: XMLTABLE(('/ROWS/ROW'::text) PASSING (xmldata.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME/text()'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
 (7 rows)
 
 -- XMLNAMESPACES tests
diff --git a/src/test/regress/expected/xml_2.out b/src/test/regress/expected/xml_2.out
index 112ebe47cd0..cb865a9ef77 100644
--- a/src/test/regress/expected/xml_2.out
+++ b/src/test/regress/expected/xml_2.out
@@ -1004,7 +1004,7 @@ SELECT  xmltable.*
                          PASSING data
                          COLUMNS id int PATH '@id',
                                   _id FOR ORDINALITY,
-                                  country_name text PATH 'COUNTRY_NAME' NOT NULL,
+                                  country_name text PATH 'COUNTRY_NAME/text()' NOT NULL,
                                   country_id text PATH 'COUNTRY_ID',
                                   region_id int PATH 'REGION_ID',
                                   size float PATH 'SIZE',
@@ -1026,7 +1026,7 @@ CREATE VIEW xmltableview1 AS SELECT  xmltable.*
                          PASSING data
                          COLUMNS id int PATH '@id',
                                   _id FOR ORDINALITY,
-                                  country_name text PATH 'COUNTRY_NAME' NOT NULL,
+                                  country_name text PATH 'COUNTRY_NAME/text()' NOT NULL,
                                   country_id text PATH 'COUNTRY_ID',
                                   region_id int PATH 'REGION_ID',
                                   size float PATH 'SIZE',
@@ -1055,7 +1055,7 @@ CREATE OR REPLACE VIEW public.xmltableview1 AS
     "xmltable".premier_name
    FROM ( SELECT xmldata.data
            FROM xmldata) x,
-    LATERAL XMLTABLE(('/ROWS/ROW'::text) PASSING (x.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
+    LATERAL XMLTABLE(('/ROWS/ROW'::text) PASSING (x.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME/text()'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
 EXPLAIN (COSTS OFF) SELECT * FROM xmltableview1;
                QUERY PLAN                
 -----------------------------------------
@@ -1065,15 +1065,15 @@ EXPLAIN (COSTS OFF) SELECT * FROM xmltableview1;
 (3 rows)
 
 EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
-                                                                                                                                                                                                                        QUERY PLAN                                                                                                                                                                                                                         
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+                                                                                                                                                                                                                            QUERY PLAN                                                                                                                                                                                                                            
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Nested Loop
    Output: "xmltable".id, "xmltable"._id, "xmltable".country_name, "xmltable".country_id, "xmltable".region_id, "xmltable".size, "xmltable".unit, "xmltable".premier_name
    ->  Seq Scan on public.xmldata
          Output: xmldata.data
    ->  Table Function Scan on "xmltable"
          Output: "xmltable".id, "xmltable"._id, "xmltable".country_name, "xmltable".country_id, "xmltable".region_id, "xmltable".size, "xmltable".unit, "xmltable".premier_name
-         Table Function Call: XMLTABLE(('/ROWS/ROW'::text) PASSING (xmldata.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
+         Table Function Call: XMLTABLE(('/ROWS/ROW'::text) PASSING (xmldata.data) COLUMNS id integer PATH ('@id'::text), _id FOR ORDINALITY, country_name text PATH ('COUNTRY_NAME/text()'::text) NOT NULL, country_id text PATH ('COUNTRY_ID'::text), region_id integer PATH ('REGION_ID'::text), size double precision PATH ('SIZE'::text), unit text PATH ('SIZE/@unit'::text), premier_name text DEFAULT ('not specified'::text) PATH ('PREMIER_NAME'::text))
 (7 rows)
 
 -- XMLNAMESPACES tests
diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql
index cb96e180053..c223603a1f2 100644
--- a/src/test/regress/sql/xml.sql
+++ b/src/test/regress/sql/xml.sql
@@ -349,7 +349,7 @@ SELECT  xmltable.*
                          PASSING data
                          COLUMNS id int PATH '@id',
                                   _id FOR ORDINALITY,
-                                  country_name text PATH 'COUNTRY_NAME' NOT NULL,
+                                  country_name text PATH 'COUNTRY_NAME/text()' NOT NULL,
                                   country_id text PATH 'COUNTRY_ID',
                                   region_id int PATH 'REGION_ID',
                                   size float PATH 'SIZE',
@@ -362,7 +362,7 @@ CREATE VIEW xmltableview1 AS SELECT  xmltable.*
                          PASSING data
                          COLUMNS id int PATH '@id',
                                   _id FOR ORDINALITY,
-                                  country_name text PATH 'COUNTRY_NAME' NOT NULL,
+                                  country_name text PATH 'COUNTRY_NAME/text()' NOT NULL,
                                   country_id text PATH 'COUNTRY_ID',
                                   region_id int PATH 'REGION_ID',
                                   size float PATH 'SIZE',