[SPARK-49641][DOCS] Include table_funcs and variant_funcs in the …

…built-in function list doc

### What changes were proposed in this pull request?
The pr aims to include `table_funcs` and `variant_funcs` in the built-in function list doc.

### Why are the changes needed?
I found that some functions were not involved in our docs, such as `sql_keywords()`, `variant_explode`, etc.
Let's include them to improve the user experience for end-users.

### Does this PR introduce _any_ user-facing change?
Yes, only for sql api docs.

### How was this patch tested?
- Pass GA
- Manually check.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes apache#48106 from panbingkun/SPARK-49641.

Authored-by: panbingkun <panbingkun@baidu.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>

docs/sql-ref-functions-builtin.md

@@ -116,3 +116,13 @@ license: |
 {% include_api_gen generated-generator-funcs-table.html %}
 #### Examples
 {% include_api_gen generated-generator-funcs-examples.html %}
+
+### Table Functions
+{% include_api_gen generated-table-funcs-table.html %}
+#### Examples
+{% include_api_gen generated-table-funcs-examples.html %}
+
+### Variant Functions
+{% include_api_gen generated-variant-funcs-table.html %}
+#### Examples
+{% include_api_gen generated-variant-funcs-examples.html %}

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/basicLogicalOperators.scala

@@ -992,12 +992,18 @@ object Range {
     castAndEval[Int](expression, IntegerType, paramIndex, paramName)
 }
 
+// scalastyle:off line.size.limit
 @ExpressionDescription(
   usage = """
-    _FUNC_(start: long, end: long, step: long, numSlices: integer)
-    _FUNC_(start: long, end: long, step: long)
-    _FUNC_(start: long, end: long)
-    _FUNC_(end: long)""",
+    _FUNC_(start[, end[, step[, numSlices]]]) / _FUNC_(end) - Returns a table of values within a specified range.
+  """,
+  arguments = """
+    Arguments:
+      * start - An optional BIGINT literal defaulted to 0, marking the first value generated.
+      * end - A BIGINT literal marking endpoint (exclusive) of the number generation.
+      * step - An optional BIGINT literal defaulted to 1, specifying the increment used when generating values.
+      * numParts - An optional INTEGER literal specifying how the production of rows is spread across partitions.
+  """,
   examples = """
     Examples:
       > SELECT * FROM _FUNC_(1);
@@ -1023,6 +1029,7 @@ object Range {
   """,
   since = "2.0.0",
   group = "table_funcs")
+// scalastyle:on line.size.limit
 case class Range(
     start: Long,
     end: Long,

sql/core/src/main/scala/org/apache/spark/sql/api/python/PythonSQLUtils.scala

@@ -29,7 +29,7 @@ import org.apache.spark.internal.LogKeys.CLASS_LOADER
 import org.apache.spark.security.SocketAuthServer
 import org.apache.spark.sql.{internal, Column, DataFrame, Row, SparkSession}
 import org.apache.spark.sql.catalyst.{CatalystTypeConverters, InternalRow}
-import org.apache.spark.sql.catalyst.analysis.FunctionRegistry
+import org.apache.spark.sql.catalyst.analysis.{FunctionRegistry, TableFunctionRegistry}
 import org.apache.spark.sql.catalyst.encoders.ExpressionEncoder
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.parser.CatalystSqlParser
@@ -69,7 +69,10 @@ private[sql] object PythonSQLUtils extends Logging {
 
   // This is needed when generating SQL documentation for built-in functions.
   def listBuiltinFunctionInfos(): Array[ExpressionInfo] = {
-    FunctionRegistry.functionSet.flatMap(f => FunctionRegistry.builtin.lookupFunction(f)).toArray
+    (FunctionRegistry.functionSet.flatMap(f => FunctionRegistry.builtin.lookupFunction(f)) ++
+      TableFunctionRegistry.functionSet.flatMap(
+        f => TableFunctionRegistry.builtin.lookupFunction(f))).
+      groupBy(_.getName).map(v => v._2.head).toArray
   }
 
   private def listAllSQLConfigs(): Seq[(String, String, String, String)] = {

sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala

@@ -111,10 +111,13 @@ class SQLQuerySuite extends QueryTest with SharedSparkSession with AdaptiveSpark
   }
 
   test("SPARK-34678: describe functions for table-valued functions") {
+    sql("describe function range").show(false)
     checkKeywordsExist(sql("describe function range"),
       "Function: range",
       "Class: org.apache.spark.sql.catalyst.plans.logical.Range",
-      "range(end: long)"
+      "range(start[, end[, step[, numSlices]]])",
+      "range(end)",
+      "Returns a table of values within a specified range."
     )
   }
 

sql/gen-sql-functions-docs.py

@@ -36,6 +36,7 @@
     "bitwise_funcs", "conversion_funcs", "csv_funcs",
     "xml_funcs", "lambda_funcs", "collection_funcs",
     "url_funcs", "hash_funcs", "struct_funcs",
+    "table_funcs", "variant_funcs"
 }