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From: vdiravka <git@git.apache.org>
To: dev@drill.apache.org
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References: <git-pr-541-drill@git.apache.org>
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Subject: [GitHub] drill pull request #541: DRILL-4673: Implement "DROP TABLE IF EXISTS" for dr...
Content-Type: text/plain
Message-Id: <20160720185359.892D4E04BA@git1-us-west.apache.org>
Date: Wed, 20 Jul 2016 18:53:59 +0000 (UTC)
archived-at: Wed, 20 Jul 2016 18:54:01 -0000

Github user vdiravka commented on a diff in the pull request:

    https://github.com/apache/drill/pull/541#discussion_r71585003
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/DropTableIfExistsHandler.java ---
    @@ -28,47 +30,57 @@
     import org.apache.drill.exec.physical.PhysicalPlan;
     import org.apache.drill.exec.planner.sql.DirectPlan;
     import org.apache.drill.exec.planner.sql.SchemaUtilites;
    -import org.apache.drill.exec.planner.sql.parser.SqlDropTable;
    +import org.apache.drill.exec.planner.sql.parser.SqlDropTableIfExists;
     import org.apache.drill.exec.store.AbstractSchema;
     
     // SqlHandler for dropping a table.
    -public class DropTableHandler extends DefaultSqlHandler {
    +public class DropTableIfExistsHandler extends DefaultSqlHandler {
     
    -  private static org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(DropTableHandler.class);
    +  private static org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(DropTableIfExistsHandler.class);
     
    -  public DropTableHandler(SqlHandlerConfig config) {
    +  public DropTableIfExistsHandler(SqlHandlerConfig config) {
         super(config);
       }
     
       /**
    -   * Function resolves the schema and invokes the drop method. Raises an exception if the schema is
    -   * immutable.
    -   * @param sqlNode - Table name identifier
    -   * @return - Single row indicating drop succeeded, raise exception otherwise
    +   * Function resolves the schema and invokes the drop method
    +   * (while IF EXISTS statement is used function invokes the drop method only if table exists).
    +   * Raises an exception if the schema is immutable.
    +   * @param sqlNode - SqlDropTableIfExists (SQL parse tree of drop table [if exists] query)
    +   * @return - Single row indicating drop succeeded or table is not found while IF EXISTS statement is used,
    +   * raise exception otherwise
        * @throws ValidationException
        * @throws RelConversionException
        * @throws IOException
        */
       @Override
       public PhysicalPlan getPlan(SqlNode sqlNode) throws ValidationException, RelConversionException, IOException {
     
    -    SqlDropTable dropTableNode = ((SqlDropTable) sqlNode);
    -    SqlIdentifier tableIdentifier = dropTableNode.getTableIdentifier();
    +    SqlDropTableIfExists dropTableIfExistsNode = ((SqlDropTableIfExists) sqlNode);
    +    SqlIdentifier tableIdentifier = dropTableIfExistsNode.getTableIdentifier();
     
         SchemaPlus defaultSchema = config.getConverter().getDefaultSchema();
         AbstractSchema drillSchema = null;
     
         if (tableIdentifier != null) {
    -      drillSchema = SchemaUtilites.resolveToMutableDrillSchema(defaultSchema, dropTableNode.getSchema());
    +      drillSchema = SchemaUtilites.resolveToMutableDrillSchema(defaultSchema, dropTableIfExistsNode.getSchema());
         }
     
    -    String tableName = ((SqlDropTable) sqlNode).getName();
    +    String tableName = dropTableIfExistsNode.getName();
         if (drillSchema == null) {
           throw UserException.validationError()
               .message("Invalid table_name [%s]", tableName)
               .build(logger);
         }
     
    +    if (dropTableIfExistsNode.checkTableExistence()) {
    +      final Table tableToDrop = SqlHandlerUtil.getTableFromSchema(drillSchema, tableName);
    +      if (tableToDrop == null || tableToDrop.getJdbcTableType() != Schema.TableType.TABLE) {
    --- End diff --
    
    I checked such query `drop table if exists hbase.TestTableNullStr` and found that the message is proper and same like for `DROP TABLE` statement: `PARSE ERROR: Unable to create or drop tables/views. Schema [hbase] is immutable.`.


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