[SPARK-20380][SQL] Unable to set/unset table comment property using A…

…LTER TABLE SET/UNSET TBLPROPERTIES ddl

### What changes were proposed in this pull request?
Table comment was not getting  set/unset using **ALTER TABLE  SET/UNSET TBLPROPERTIES** query
eg: ALTER TABLE table_with_comment SET TBLPROPERTIES("comment"= "modified comment)
 when user alter the table properties  and adds/updates table comment,table comment which is a field  of **CatalogTable**  instance is not getting updated and  old table comment if exists was shown to user, inorder  to handle this issue, update the comment field value in **CatalogTable** with the newly added/modified comment along with other table level properties when user executes **ALTER TABLE  SET TBLPROPERTIES** query.

This pr has also taken care of unsetting the table comment when user executes query  **ALTER TABLE  UNSET TBLPROPERTIES** inorder to unset or remove table comment.
eg: ALTER TABLE table_comment UNSET TBLPROPERTIES IF EXISTS ('comment')

### How was this patch tested?
Added test cases  as part of **SQLQueryTestSuite** for verifying  table comment using desc formatted table query after adding/modifying table comment as part of **AlterTableSetPropertiesCommand** and unsetting the table comment using **AlterTableUnsetPropertiesCommand**.

Author: sujith71955 <[email protected]>

Closes #17649 from sujith71955/alter_table_comment.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/InMemoryCatalog.scala

@@ -216,8 +216,8 @@ class InMemoryCatalog(
       } else {
         tableDefinition
       }
-
-      catalog(db).tables.put(table, new TableDesc(tableWithLocation))
+      val tableProp = tableWithLocation.properties.filter(_._1 != "comment")
+      catalog(db).tables.put(table, new TableDesc(tableWithLocation.copy(properties = tableProp)))
     }
   }
 
@@ -298,7 +298,9 @@ class InMemoryCatalog(
     assert(tableDefinition.identifier.database.isDefined)
     val db = tableDefinition.identifier.database.get
     requireTableExists(db, tableDefinition.identifier.table)
-    catalog(db).tables(tableDefinition.identifier.table).table = tableDefinition
+    val updatedProperties = tableDefinition.properties.filter(kv => kv._1 != "comment")
+    val newTableDefinition = tableDefinition.copy(properties = updatedProperties)
+    catalog(db).tables(tableDefinition.identifier.table).table = newTableDefinition
   }
 
   override def alterTableSchema(

sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala

@@ -231,8 +231,12 @@ case class AlterTableSetPropertiesCommand(
     val catalog = sparkSession.sessionState.catalog
     val table = catalog.getTableMetadata(tableName)
     DDLUtils.verifyAlterTableType(catalog, table, isView)
-    // This overrides old properties
-    val newTable = table.copy(properties = table.properties ++ properties)
+    // This overrides old properties and update the comment parameter of CatalogTable
+    // with the newly added/modified comment since CatalogTable also holds comment as its
+    // direct property.
+    val newTable = table.copy(
+      properties = table.properties ++ properties,
+      comment = properties.get("comment"))
     catalog.alterTable(newTable)
     Seq.empty[Row]
   }
@@ -267,8 +271,10 @@ case class AlterTableUnsetPropertiesCommand(
         }
       }
     }
+    // If comment is in the table property, we reset it to None
+    val tableComment = if (propKeys.contains("comment")) None else table.properties.get("comment")
     val newProperties = table.properties.filter { case (k, _) => !propKeys.contains(k) }
-    val newTable = table.copy(properties = newProperties)
+    val newTable = table.copy(properties = newProperties, comment = tableComment)
     catalog.alterTable(newTable)
     Seq.empty[Row]
   }

sql/core/src/test/resources/sql-tests/inputs/describe-table-after-alter-table.sql

@@ -0,0 +1,29 @@
+CREATE TABLE table_with_comment (a STRING, b INT, c STRING, d STRING) USING parquet COMMENT 'added';
+
+DESC FORMATTED table_with_comment;
+
+-- ALTER TABLE BY MODIFYING COMMENT
+ALTER TABLE table_with_comment SET TBLPROPERTIES("comment"= "modified comment", "type"= "parquet");
+
+DESC FORMATTED table_with_comment;
+
+-- DROP TEST TABLE
+DROP TABLE table_with_comment;
+
+-- CREATE TABLE WITHOUT COMMENT
+CREATE TABLE table_comment (a STRING, b INT) USING parquet;
+
+DESC FORMATTED table_comment;
+
+-- ALTER TABLE BY ADDING COMMENT
+ALTER TABLE table_comment SET TBLPROPERTIES(comment = "added comment");
+
+DESC formatted table_comment;
+
+-- ALTER UNSET PROPERTIES COMMENT
+ALTER TABLE table_comment UNSET TBLPROPERTIES IF EXISTS ('comment');
+
+DESC FORMATTED table_comment;
+
+-- DROP TEST TABLE
+DROP TABLE table_comment;

sql/core/src/test/resources/sql-tests/results/describe-table-after-alter-table.sql.out

@@ -0,0 +1,161 @@
+-- Automatically generated by SQLQueryTestSuite
+-- Number of queries: 12
+
+
+-- !query 0
+CREATE TABLE table_with_comment (a STRING, b INT, c STRING, d STRING) USING parquet COMMENT 'added'
+-- !query 0 schema
+struct<>
+-- !query 0 output
+
+
+
+-- !query 1
+DESC FORMATTED table_with_comment
+-- !query 1 schema
+struct<col_name:string,data_type:string,comment:string>
+-- !query 1 output
+# col_name          	data_type           	comment             
+a                   	string              	                    
+b                   	int                 	                    
+c                   	string              	                    
+d                   	string              	                    
+
+# Detailed Table Information	                    	                    
+Database            	default             	                    
+Table               	table_with_comment  	                    
+Created [not included in comparison]
+Last Access [not included in comparison]
+Type                	MANAGED             	                    
+Provider            	parquet             	                    
+Comment             	added               	                    
+Location [not included in comparison]sql/core/spark-warehouse/table_with_comment
+
+
+-- !query 2
+ALTER TABLE table_with_comment SET TBLPROPERTIES("comment"= "modified comment", "type"= "parquet")
+-- !query 2 schema
+struct<>
+-- !query 2 output
+
+
+
+-- !query 3
+DESC FORMATTED table_with_comment
+-- !query 3 schema
+struct<col_name:string,data_type:string,comment:string>
+-- !query 3 output
+# col_name          	data_type           	comment             
+a                   	string              	                    
+b                   	int                 	                    
+c                   	string              	                    
+d                   	string              	                    
+
+# Detailed Table Information	                    	                    
+Database            	default             	                    
+Table               	table_with_comment  	                    
+Created [not included in comparison]
+Last Access [not included in comparison]
+Type                	MANAGED             	                    
+Provider            	parquet             	                    
+Comment             	modified comment    	                    
+Properties          	[type=parquet]      	                    
+Location [not included in comparison]sql/core/spark-warehouse/table_with_comment
+
+
+-- !query 4
+DROP TABLE table_with_comment
+-- !query 4 schema
+struct<>
+-- !query 4 output
+
+
+
+-- !query 5
+CREATE TABLE table_comment (a STRING, b INT) USING parquet
+-- !query 5 schema
+struct<>
+-- !query 5 output
+
+
+
+-- !query 6
+DESC FORMATTED table_comment
+-- !query 6 schema
+struct<col_name:string,data_type:string,comment:string>
+-- !query 6 output
+# col_name          	data_type           	comment             
+a                   	string              	                    
+b                   	int                 	                    
+
+# Detailed Table Information	                    	                    
+Database            	default             	                    
+Table               	table_comment       	                    
+Created [not included in comparison]
+Last Access [not included in comparison]
+Type                	MANAGED             	                    
+Provider            	parquet             	                    
+Location [not included in comparison]sql/core/spark-warehouse/table_comment
+
+
+-- !query 7
+ALTER TABLE table_comment SET TBLPROPERTIES(comment = "added comment")
+-- !query 7 schema
+struct<>
+-- !query 7 output
+
+
+
+-- !query 8
+DESC formatted table_comment
+-- !query 8 schema
+struct<col_name:string,data_type:string,comment:string>
+-- !query 8 output
+# col_name          	data_type           	comment             
+a                   	string              	                    
+b                   	int                 	                    
+
+# Detailed Table Information	                    	                    
+Database            	default             	                    
+Table               	table_comment       	                    
+Created [not included in comparison]
+Last Access [not included in comparison]
+Type                	MANAGED             	                    
+Provider            	parquet             	                    
+Comment             	added comment       	                    
+Location [not included in comparison]sql/core/spark-warehouse/table_comment
+
+
+-- !query 9
+ALTER TABLE table_comment UNSET TBLPROPERTIES IF EXISTS ('comment')
+-- !query 9 schema
+struct<>
+-- !query 9 output
+
+
+
+-- !query 10
+DESC FORMATTED table_comment
+-- !query 10 schema
+struct<col_name:string,data_type:string,comment:string>
+-- !query 10 output
+# col_name          	data_type           	comment             
+a                   	string              	                    
+b                   	int                 	                    
+
+# Detailed Table Information	                    	                    
+Database            	default             	                    
+Table               	table_comment       	                    
+Created [not included in comparison]
+Last Access [not included in comparison]
+Type                	MANAGED             	                    
+Provider            	parquet             	                    
+Location [not included in comparison]sql/core/spark-warehouse/table_comment
+
+
+-- !query 11
+DROP TABLE table_comment
+-- !query 11 schema
+struct<>
+-- !query 11 output
+