[SPARK-22999][SQL] show databases like command' can remove the like k…

…eyword

## What changes were proposed in this pull request?

SHOW DATABASES (LIKE pattern = STRING)? Can be like the back increase?
When using this command, LIKE keyword can be removed.
You can refer to the SHOW TABLES command, SHOW TABLES 'test *' and SHOW TABELS like 'test *' can be used.
Similarly SHOW DATABASES 'test *' and SHOW DATABASES like 'test *' can be used.

## How was this patch tested?
unit tests   manual tests
Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: guoxiaolong <[email protected]>

Closes #20194 from guoxiaolongzte/SPARK-22999.

(cherry picked from commit 42a1a15)
Signed-off-by: gatorsmile <[email protected]>

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -141,7 +141,7 @@ statement
         (LIKE? pattern=STRING)?                                        #showTables
     | SHOW TABLE EXTENDED ((FROM | IN) db=identifier)?
         LIKE pattern=STRING partitionSpec?                             #showTable
-    | SHOW DATABASES (LIKE pattern=STRING)?                            #showDatabases
+    | SHOW DATABASES (LIKE? pattern=STRING)?                            #showDatabases
     | SHOW TBLPROPERTIES table=tableIdentifier
         ('(' key=tablePropertyKey ')')?                                #showTblProperties
     | SHOW COLUMNS (FROM | IN) tableIdentifier

sql/core/src/test/scala/org/apache/spark/sql/execution/command/DDLSuite.scala

@@ -991,6 +991,10 @@ abstract class DDLSuite extends QueryTest with SQLTestUtils {
       sql("SHOW DATABASES LIKE '*db1A'"),
       Row("showdb1a") :: Nil)
 
+    checkAnswer(
+      sql("SHOW DATABASES '*db1A'"),
+      Row("showdb1a") :: Nil)
+
     checkAnswer(
       sql("SHOW DATABASES LIKE 'showdb1A'"),
       Row("showdb1a") :: Nil)