Add proper checks to handle cases where SchemaTablePrefix schemaName is null

Author: BryanCutler

presto-druid/src/main/java/com/facebook/presto/druid/DruidMetadata.java

@@ -192,7 +192,7 @@ public Optional<ConnectorOutputMetadata> finishCreateTable(ConnectorSession sess
     private List<SchemaTableName> listTables(ConnectorSession session, SchemaTablePrefix prefix)
     {
         if (prefix.getTableName() == null) {
-            return listTables(session, Optional.of(prefix.getSchemaName()));
+            return listTables(session, Optional.ofNullable(prefix.getSchemaName()));
         }
         return ImmutableList.of(prefix.toSchemaTableName());
     }

presto-google-sheets/src/main/java/com/facebook/presto/google/sheets/SheetsMetadata.java

@@ -159,7 +159,7 @@ public Map<SchemaTableName, List<ColumnMetadata>> listTableColumns(ConnectorSess
     {
         requireNonNull(prefix, "prefix is null");
         ImmutableMap.Builder<SchemaTableName, List<ColumnMetadata>> columns = ImmutableMap.builder();
-        for (SchemaTableName tableName : listTables(session, Optional.of(prefix.getSchemaName()))) {
+        for (SchemaTableName tableName : listTables(session, Optional.ofNullable(prefix.getSchemaName()))) {
             Optional<ConnectorTableMetadata> tableMetadata = getTableMetadata(session, tableName);
             // table can disappear during listing operation
             if (tableMetadata.isPresent()) {

presto-hudi/src/main/java/com/facebook/presto/hudi/HudiMetadata.java

@@ -170,7 +170,7 @@ public ColumnMetadata getColumnMetadata(ConnectorSession session, ConnectorTable
     @Override
     public Map<SchemaTableName, List<ColumnMetadata>> listTableColumns(ConnectorSession session, SchemaTablePrefix prefix)
     {
-        List<SchemaTableName> tables = prefix.getTableName() != null ? singletonList(prefix.toSchemaTableName()) : listTables(session, Optional.of(prefix.getSchemaName()));
+        List<SchemaTableName> tables = prefix.getTableName() != null ? singletonList(prefix.toSchemaTableName()) : listTables(session, Optional.ofNullable(prefix.getSchemaName()));
 
         ImmutableMap.Builder<SchemaTableName, List<ColumnMetadata>> columns = ImmutableMap.builder();
         for (SchemaTableName table : tables) {

presto-iceberg/src/main/java/com/facebook/presto/iceberg/IcebergHiveMetadata.java

@@ -472,7 +472,7 @@ public Map<SchemaTableName, ConnectorViewDefinition> getViews(ConnectorSession s
     {
         ImmutableMap.Builder<SchemaTableName, ConnectorViewDefinition> views = ImmutableMap.builder();
         List<SchemaTableName> tableNames;
-        if (prefix.getTableName() != null) {
+        if (prefix.getSchemaName() != null && prefix.getTableName() != null) {
             tableNames = ImmutableList.of(new SchemaTableName(prefix.getSchemaName(), prefix.getTableName()));
         }
         else {

presto-iceberg/src/main/java/com/facebook/presto/iceberg/IcebergNativeMetadata.java

@@ -270,11 +270,11 @@ public Map<SchemaTableName, ConnectorViewDefinition> getViews(ConnectorSession s
         Catalog catalog = catalogFactory.getCatalog(session);
         if (catalog instanceof ViewCatalog) {
             List<SchemaTableName> tableNames;
-            if (prefix.getTableName() != null) {
+            if (prefix.getSchemaName() != null && prefix.getTableName() != null) {
                 tableNames = ImmutableList.of(new SchemaTableName(prefix.getSchemaName(), prefix.getTableName()));
             }
             else {
-                tableNames = listViews(session, Optional.of(prefix.getSchemaName()));
+                tableNames = listViews(session, Optional.ofNullable(prefix.getSchemaName()));
             }
 
             for (SchemaTableName schemaTableName : tableNames) {