This is the source-only release of the Apache Trafodion (incubating) project. In addition to including a number of new features and improvements across the project, the focus of this release is to comply with Apache release guidelines.
Build instructions are available here.
The following platforms are supported in this release.
|Operating Systems||CentOS 6.5 – 6.7|
|Hadoop Distributions||Cloudera distributions CDH 5.3.x
Hortonworks distribution HDP 2.2
|Java Version||JDK 1.7.0_67 or newer|
|HBase Version||HBase 0.98.x|
This release contains the following new features.
|Marketability, Infrastructure, and Scalability||
|High Availability (HA) and Distributed Transaction Management (DTM)||
This release contains fixes to around 96 defects, including 17 critical defects, 53 high defects, 20 medium defects, and two low defects. Those defects were filed through Launchpad.
EXECUTE.BATCH update creates core-file
Symptom: EXECUTE.BATCH hangs for a long time doing updates, and the update creates a core file.
Cause: To be determined.
Solution: Batch updates and ODBC row arrays do not currently work.
Random update statistics failures with HBase OutOfOrderScannerNextException
Symptom: While running update statistics commands, you see HBase OutOfOrderScannerNextException errors.
Cause: The default hbase.rpc.timeout and hbase.client.scanner.timeout.period values might be too low given the size of the tables. Sampling in update statistics is implemented using the HBase Random RowFilter. For very large tables with several billion rows, the sampling ratio required to get a sample of 1 million rows is very small. This can result in HBase client connection timeout errors since there may be no row returned by a RegionServer for an extended period of time.
Solution: Increase the hbase.rpc.timeout and hbase.client.scanner.timeout.period values. We have found that increasing those values to 600 seconds (10 minutes) might sometimes prevent many timeout-related errors. For more information, see the HBase Configuration and Fine Tuning Recommendations.
If increasing the hbase.rpc.timeout and hbase.client.scanner.timeout.period values does not work, try increasing the chosen sampling size. Choose a sampling percentage higher than the default setting of 1 million rows for large tables. For example, suppose table T has one billion rows. The following UPDATE STATISTICS statement will sample a million rows, or approximately one-tenth of one percent of the total rows:
update statistics for table T on every column sample;
To sample one percent of the rows, regardless of the table size, you must explicitly state the sampling rate as follows:
update statistics for table T on every column sample random 1 percent;
Following update statistics, stats do not take effect immediately
Symptom: Immediately following an update statistics operation, the generated query plan does not seem to reflect the existence of statistics. For example, in a session, you create, and populate a table and then run update statistics on the table, prepare a query, and exit. A serial plan is generated and the estimated cardinality is 100 for both tables. In a new session, you prepare the same query, and a parallel plan is generated where the estimated cardinality reflects the statistics.
Cause: This is a day-one issue.
Solution: Retry the query after two minutes. Set CQD HIST_NO_STATS_REFRESH_INTERVAL to ‘0’. Run an UPDATE STATISTICS statement. Perform DML operations in a different session.