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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-1115) Provide a SQL command to turn tracing on/off
Date Mon, 16 Feb 2015 19:14:11 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-1115?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14323151#comment-14323151
] 

James Taylor commented on PHOENIX-1115:
---------------------------------------

Thanks for the patch, [~rajeshbabu]. Here's some feedback:
- Rather than surfacing this through an ALTER SESSION command, how about a TRACE ON/OFF command.
It'll be similar in terms of implementation, but instead of treating this as a mutate statement,
treat it as a query. It'll return one row with a single TRACE_ID BIGINT column value. That
way, when invoked from sqlline, it'll print out the trace ID (as if it was a SELECT statement),
and when invoked programmatically (i.e. hopefully someone will build a tool for this), then
you could do a resultSet.getLong(1) to get the top level trace ID. The other advantage of
having a specific command for it is that we can add various options and it'll fail if the
user gets them wrong.
- Rather than write some relatively hacky print out code (which is after all just a nearly
unusable way of visualizing the trace info), we can surface this similar to the way MySQL
does: allow people to query the SYSTEM.TRACE table directly (or provide a simple VIEW on top
named INFORMATION_SCHEMA.OPTIMIZER_TRACE which might be even better, though fixing PHOENIX-1507
might be a prereq). That way, we don't have to support other tracing output options, as the
user can take advantage of sqlline being able to output query results in CSV format (if they
want to export the trace information for visualization in Excel or some other tool, for example).
On our website, we'll document a few canned queries to get the user started:
{code}
SELECT description, hostname, start_time, end_time - start_time duration
FROM SYSTEM.TRACING
WHERE trace_id = <your trace id>
ORDER BY start_time;

-- Select trace ID of last SQL statement
-- TODO: Verify this
SELECT trace_id, description
FROM SYSTEM.TRACING
WHERE parent_id = <your trace id>
ORDER BY trace_id DESC
LIMIT 1;

-- Select 10 longest running operations for a given trace
-- TODO: Try grouping by SPAN_ID instead and select MAX(description)
-- as it's likely the same and will be more efficient.
SELECT hostname, description, MAX(start_time - end_time)
FROM SYSTEM.TRACING
WHERE trace_id = <your trace id>
GROUP BY hostname, description
ORDER BY MAX(start_time - end_time)
LIMIT 10;
{code}
- Is the code below to group all batched Put mutations info a single span, and if so, can
we just always do this (but without the instanceof and check for Sampler.ALWAYS), as there's
no harm in doing this, right?
{code}
@@ -186,6 +194,7 @@ public class PhoenixStatement implements Statement, SQLCloseable, org.apache.pho
     private int maxRows;
     private int fetchSize = -1;
     private int queryTimeout;
+    private TraceScope trace = null;
     
     public PhoenixStatement(PhoenixConnection connection) {
         this.connection = connection;
@@ -267,6 +276,14 @@ public class PhoenixStatement implements Statement, SQLCloseable, org.apache.pho
                 build().buildException();
         }
         try {
+            if (connection.isSqlTraceOn() && connection.getAutoCommit()
+                    && connection.getSampler().equals(Sampler.ALWAYS)
+                    && !(stmt instanceof AlterSessionStatement)) {
+                if(trace == null) {
+                    TraceScope scope = Tracing.startNewSpan(connection, "Executing mutation
statement");
+                    trace = scope;
+                }
+            }
             return CallRunner
                     .run(
                         new CallRunner.CallableThrowable<Integer, SQLException>() {
{code}

> Provide a SQL command to turn tracing on/off
> --------------------------------------------
>
>                 Key: PHOENIX-1115
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1115
>             Project: Phoenix
>          Issue Type: Sub-task
>    Affects Versions: 5.0.0, 4.1
>            Reporter: James Taylor
>            Assignee: Rajeshbabu Chintaguntla
>         Attachments: PHOENIX-1115.patch, PHOENIX-1115_v2.patch, Screen Shot 2014-11-21
at 3.41.41 PM.png, tracing_in_different_rdbms.pdf
>
>
> Provide a SQL command that turns tracing on and off. For example, Oracle has this:
> {code}
> ALTER SESSION SET sql_trace = true;
> ALTER SESSION SET sql_trace = false;
> {code}
> We might consider allowing the sampling rate to be set as well.



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