Fix for hang encountered during hive tests. Added proper copyright. Added comment to make it clear to readers of the code. Hive tests have been hanging for quite a while on the official slave machines. The cause for this particular hang was that the main thread was destroying the cursor (ExLobCursor) object . The worker thread was kind of slow and it continues to access the cursor after the main thread had destroyed it. pthread calls exhibit undefined behavior when uninitialized mutex or condition variables are accessed. Added code to prevent this timing issue in the worker threads.
Added trace utlitlty to diagnose hangs and execution issues. The trace messages look like this and get logged into trace file on the local directory named trace_threads.<pid>. It is controlled by an environment variable TRACE_HDFS_THREAD_ACTIONS.The envvar is checked only ones and the file handle is checked each time the trace needs to be done. If file handle is NULL, no message is logged.
LOB datatype infrastructure support Technology preview. More changes expected as part of this work before it is user ready. blueprint lob-support
This checkin contains basic support for create blob/clob datatypes. The feature is disabled by default. Instructions on how to enable are listed below. New test executor/TEST130 that turns the feature on and tests out the functionality. New mxlobsrvr process will be started as part of sqstart. Create and drop of tables with LOB columns. No support for alter. DML support for LOB datatypes. Insert, update and deletes. Joins of 2 tables with LOB columns are allowed but joins on LOB columns temselves are not allowed. Insert-select from one LOB table another not yet supported. Link to document from the blueprint will be added shortly.
To enable and try LOBs: On a developer workstation :
cqd TRAF_BLOB_AS_VARCHAR 'OFF';
On a cluster after installing the code 2 steps are needed:
This checkin includes several merges from the mainline and each of the lines below represents one commit to the project branch where this work was done. ` -Turning off LOB code by default. But turning it on in executor/TEST130 just to ensure testing the code path. -Support for showddl and some syntax for external files and stream. -LOB regression test -Workaround for dtm issue LP 378167 -Changes to make append work. Changes to use lob heap. -Fix for using system heap for all LOB allocations and handling NULLs. -Added workaround for cursor delete issue. LP 1376969 -Fixes for update. -Parser changes for exe_util_lob_extract -Pull in lob extract code -Adding mxlobsrvr directory
-Fixed the LOB interface to use 2 new params for cursor fetches. They do not overload the LOB Handle and LOB handle length anymore. Added a flag to lobGlobals to indetify it's a hive access. Cleaned up parser code.
-LOB support for create,drop,insert,delete,select.