Bobby Durrett's DBA Blog

A few days or weeks ago I saw a Twitter post about database links failing on Oracle databases next year. So, I have researched this issue. My company has a bunch of Oracle databases with a web of database links connecting them. After researching this for a while I have convinced myself that our company will not experience an issue. I want to share some of what I have found in this post.

First, I have read some helpful documents on Oracle’s support site. I recommend that you review these if you want to understand the issue:

Mandatory Patching Requirement for Database Versions 11.2.0.3 or Earlier, Using DB Links (Doc ID 2335265.1)

Recommended patches and actions for Oracle databases versions 12.1.0.1, 11.2.0.3 and earlier – before June 2019 (Doc ID 2361478.1)

Master Note: Overview for SCN issues (Doc ID 1503937.1)

System Change Number (SCN), Headroom, Security and Patch Information (Doc ID 1376995.1)

ORA-19706 and Related Alert Log Messages (Doc ID 1393360.1)

Bug 23130347 : HIGH SCN GROWTH RATE

Besides reading Oracle support documents I wanted to recreate a database link issue on a couple of test databases. My idea was to build a database that was not patched enough based on Oracle’s recommendations and one that was. Then connect them and set the date forward to after June 23, 2019 and see if I could create the issues that could happen at that time. I was not successful in recreating the issue. But I did prove out one interesting fact about database links and SCN numbers. When you use a database link the Oracle RDBMS synchronizes the SCN numbers of the two databases. Here is an example. I have 11.2.0.3.0 and 12.1.0.2 databases running on small Linux VMs on top of VirtualBox on my laptop.

Here are their SCN numbers after I create a database link between the two and before I use the database link:

NLSRTL Version 11.2.0.3.0 - Production

ORCL:SYSTEM>ORCL:SYSTEM>
     CURRENT_SCN
----------------
         1003971
         
NLSRTL Version 12.1.0.2.0 - Production

ORCL:SYSTEM>ORCL:SYSTEM>
     CURRENT_SCN
----------------
         1858602

Here are their SCN numbers after an update over a link:

NLSRTL Version 11.2.0.3.0

ORCL:SYSTEM>ORCL:SYSTEM>
     CURRENT_SCN
----------------
         1859090
 
NLSRTL Version 12.1.0.2.0

ORCL:SYSTEM>ORCL:SYSTEM>
     CURRENT_SCN
----------------
         1859091

I did the same thing with a select statement and got the same sort of synchronization of SCN numbers.

Knowing that database links cause SCNs to sync I started looking at our SCNs on all of our databases and found that there were two groups of databases with very similar SCNs. One group’s SCN was around 475,000,000,000 and the other group’s SCN was around 970,000,000,000.

But, based on the documents that I have read the max SCN for May 16th, 2018, today, is almost 16 trillion. We are under 1 trillion on our busiest system so we have a lot of headroom. The Oracle support documents say that there is some internal limit to how much your SCN can grow and Oracle bases the limit on the number of seconds since midnight January 1, 1988. You multiply the seconds by 16K SCN numbers per second to get the max SCN for today’s date. I found a lot of this math in scnhealthcheck.sql which Oracle’s Doc ID 1503937.1 includes.  I hacked it into different pieces that I found helpful but I didn’t think I should post them because it is a copyrighted script. Just download it from Oracle support and see if what I’m saying makes sense.

Anyway, after reading up on all this stuff I don’t think that the SCN issues with database links apply to us. We have far too much headroom. Maybe a company with higher transaction rate databases would be closer to the limit. We will find out on June 23, 2019 if I am right.

Bobby

So, I was at the Collaborate 2018 Oracle user group conference last week and I am on call this week. I have not posted anything about the conference so I thought I would try to get something out there.

I did my Python and Toastmasters talks. I’m not sure how people received these. Both of these talks sort of loaded extra burden on the Oracle DBAs who attended. One talk said they should learn Python and the other said they should join Toastmasters. I think both had good information and valuable advice. But I got the feeling looking into people’s eyes that I was just adding a weight to their already heavy load. Maybe next time I do some talks I should focus on teaching something that can help lighten people’s load. They should take something away from the talk that they could use right away and not have to go do a bunch of extra work. I’m not sure.

The Toastmasters talk was poorly attended just as it was at RMOUG Training days. I was able to convince the people who run the conferences to let me do the talk but it didn’t attract attendees. Maybe the next time that I do a talk on soft skills I should give specific helpful advice instead of just talking about a program that people could join. A couple of IOUG leaders at my talk made similar suggestions. I guess with the two conferences behind me I’m reviewing what I did and how I can improve. Of course people were appreciative of my efforts since I’m just a volunteer speaker. But, I would like to get better.

I think next time I talk about Python I want to do a demo. They say a picture is worth a thousand words. I think the same is true about demos. I talked about why Python is a good language for Oracle DBAs to use with just a bunch of slides. Maybe I could have made similar points in the context of a live demo. I have some Toastmasters talks coming up. I may work in a demo or two to get some practice doing that sort of talk.

I enjoyed attending the sessions. When I wasn’t presenting I attended a variety of sessions. In the past I would focus on Oracle performance tuning talks but this year I looked for other topics that are current.

I did go to two Oracle new features talks. One funny thing happened. I think both speakers talked about Oracle’s new autonomous data warehouse and how it would get rid of a lot of normal DBA work. Then both speakers went on to detail all the complex new features that are in Oracle 12.2 and 18c. It made me laugh because in the same hour talk they contradicted themselves. First they said all this DBA work is going away and then they listed a pile of new features that DBAs need to learn. Funny. I don’t buy all the autonomous stuff for a second. It is all hype like a lot of things. Think about SQL optimization. People have tried for decades to write a SQL optimizer and they still can’t make one that works. I think there are some things that we just can’t do and SQL optimization is one of them. I have no reason to think that the machine learning and AI that will supposedly drive the autonomous data warehouse will work any better than the optimizer. Time will tell.

I went to three talks on Kafka which was a little redundant. I also went to a talk on MySQL, Mongo DB, Devops, and a couple of talks related to SQL on Hadoop. I went to a couple of talks by Amazon Web Services employees including one on Oracle on RDS. I went to a couple of talks on block chain. Lastly I went to a little different talk about graph theory or network science. All of this is to say I was looking at a lot of non-Oracle stuff instead of just going to Oracle database performance sessions.

The funny thing is that I’m on a project at work that is talking about putting in a SQL on Hadoop system. I was able to apply the Hadoop stuff that I learned at Collaborate in my first day back in the office. I’m not a Hadoop expert but the exposure was valuable.

The graph theory stuff intrigues me. I learned some graph theory in the edX and OCW classes that I have worked through. I can’t help wondering if there are business or IT problems that we could be modelling with graphs in my work. I’m working on this issue of database links between older and newer versions of Oracle. I guess you could look at Oracle databases as nodes and database links as edges. But, I’m not sure beyond that.

Anyway, going to a conference always gives me a lot to think about.  It was good to do my two talks and to hear what others had to say.

Bobby

I’m leaving for Las Vegas a week from this Sunday for the Collaborate 2018 conference #C18LV.

I’m doing the same two talks that I did in Denver at RMOUG Training Days.

Here are the times and locations for the talks if you will be there at C0llaborate:

Session: 1415: Python for the Oracle DBA
Date/time: Tue, Apr 24, 2018 (09:45 AM – 10:45 AM)
Location: Jasmine H

Session: 1416: Toastmasters for the Oracle DBA
Date/time: Wed, Apr 25, 2018 (08:30 AM – 09:30 AM)
Location: South Pacific I, North Convention Center

I haven’t looked at these talks since the conference in February and I have focused my attention on other things so now I am starting to get my mind back on these talks. I am passionate about both topics so hopefully that will come across. I got good feedback at the conference in Denver so I think that those who hear my talks in Vegas will benefit from them. If you can make it to Collaborate I would love to have you attend.

Las Vegas will be just a bit warmer than the 6 degree Fahrenheit mornings that we had in Denver, so that will be fun. 🙂

Bobby

This is a quick note about a problem I had creating a Delphix virtual database clone of a production database.

This is an older 11.1.0.7 HP-UX Itanium database. I tried to make a new virtual database copy of the production database and it failed due to the following error:

ORA-07445: exception encountered: core dump [krd_flush_influx_buffers()+96] [SIGSEGV] [ADDR:0x10000000005D8] [PC
:0x400000000B415880] [Address not mapped to object] []

I only found one thing on Oracle’s support site about krd_flush_influx_buffers but it was not an exact match because it had to do with Data Guard.

So I tried various parameters and none worked. I tried setting parallel_max_servers to 0  down from 100 in production but that caused other issues. Then I remembered something about setting it to 2 so I tried that and it worked.

The strange things is that I still see a ORA-07445 krd_flush_influx_buffers error in the alert log for the successful clone. But, somehow changing the parallel_max_servers parameter to 2 allowed the various Delphix and Oracle processes to complete.

Bobby

P.S.

Today, 4/30/2020, more than 2 years after this post I have the same error on most likely the same database and setting parallel_max_servers to 2 did not solve it. I have upgraded Delphix recently.

After trying a zillion parameter options I finally got the idea of using a different 11.1.0.7 home on the same server. It is at a different patch level than the source database so normally that is not what you want. But the other Oracle home must not have the bug because the provision worked like a charm using it. After successfully provisioning the VDB on the wrong 11.1.0.7 home I used the upgrade feature to point it to the correct 11.1.0.7 home.

Maybe the useful suggestion here is that if you have a version of Oracle that has a bug that prevents you from provisioning a VDB through Delphix you can set up a new Oracle home with a different patch level that does not have the bug and do your provision on it. Then use the upgrade feature to move the VDB back to the home you wanted it on in the first place.

Bobby

This is a late post inspired by my time at RMOUG Training Days 2018. I attended two RMOUG Training Days presentations about automated cloud data warehouse database systems. The first was about Snowflake. The second was about Oracle’s coming Autonomous Data Warehouse Cloud offering. Both products seem to have the goal of automating as much as possible in a data warehouse database and neither seem to allow users to create indexes or to partition their data in the way they choose.

This raises the obvious question – do you need the ability to create indexes and define your own partitioning scheme in a data warehouse database? I have seen many situations on data warehouse databases where both are helpful. When we went to Exadata there was a push to drop all of our indexes but we did not. Also, we used partitioning to improve query performance. If we had to get rid of both features what would we have done on Exadata?

I don’t know the answer, but people say that we need more automation and less control. So, you could spin up a cloud based data warehouse database quickly and start using it. But how many knobs are left to turn when performance is slow? Do users need indexes and partitioning methods to get acceptable performance? Really, what is wrong with giving users the ability to create indexes and to partition tables in the way they want?

Time will tell whether index and partition free cloud based data warehouse database systems make it. But, for now I’m left to wonder what we are losing without these features.

Bobby

I am just getting started looking at MySQL performance tuning but I thought I would share something that I may have figured out. I’m working with a query that does a count and a group by in a subquery and it runs too long. It seems that the query reads every row from a table instead of passing a predicate into the subselect and accessing only a couple of rows. MySQL 5.7 seems to behave this way normally. I have built a simple test case to show that MySQL 5.7 works differently than Oracle 12.1 in this situation.

I build a table called TEST with about 1,000,000 rows (1,1) and one row (2,2) and put an index on the first column.

create table test(a int,b int);

insert into test values(1,1);

insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;
insert into test select * from test;

-- 1048576 rows

select count(*) from test;

create index testi on test (a);

insert into test values (2,2);

analyze table test;

Then I have a subselect with a SUM and a GROUP by and a where clause condition outside of the subselect that would cause the subselect to look at only one row – the one with values (2,2).

select sum_b from
(select a,sum(b) sum_b
from test
group by a) inner_query
where 
a=2;

This takes almost 2 seconds running in an Amazon RDS instance:

+-------+
| sum_b |
+-------+
|     2 |
+-------+
1 row in set (1.53 sec)

The corresponding Oracle query running in an on-premises Linux VM runs faster:

SQL> select sum_b from
  2  (select a,sum(b) sum_b
  3  from test
  4  group by a) inner_query
  5  where
  6  a=2;

     SUM_B
----------
         2

Elapsed: 00:00:00.08

I realize that the hardware is not the same but I think they are reasonably close. Best I can tell the Oracle version is faster because Oracle pushes the a=2 predicate into the subselect but MySQL doesn’t. The Oracle execution plan shows the a=2 predicate in the inner index scan:

--------------------------------------------------------------------------------------
| Id  | Operation                    | Name  | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |       |     1 |     6 |     4   (0)| 00:00:01 |
|   1 |  SORT GROUP BY NOSORT        |       |     1 |     6 |     4   (0)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| TEST  |     1 |     6 |     4   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN          | TESTI |     1 |       |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------------------
...
Predicate Information (identified by operation id):
---------------------------------------------------

   3 - access("A"=2)

I am still learning MySQL plans but it seems that MySQL does a full index scan:

As I said, I am new to MySQL so I may have missed some way around this. One simple solution would be to write your query without a subselect so that the predicate is in the group by query. This runs about as fast as the Oracle example above:

select sum(b) sum_b
from test
where 
a=2
group by a
--------------

+-------+
| sum_b |
+-------+
|     2 |
+-------+
1 row in set (0.10 sec)

This does a simple index lookup.

I have uploaded a zip of my Oracle and MySQL test here: zip

Maybe if you have used Oracle in the past and are now using MySQL 5.7 you should keep in mind that MySQL 5.7 does not push predicates into subqueries in the same situations that Oracle does and build your queries around this difference.

Bobby

I have uploaded a zip of my two RMOUG Training Days talks here: zip

During the Toastmasters talk there was a question about finding a club in your area.

Here is how to find a Toastmasters club near you. Go to www.toastmasters.org and click on the FIND A CLUB button. Enter your address or zip and you get a map with club locations like this:

Click on the club to see details of when it meets and whether they are open to new members.

You can call the phone number and you can visit their website if they have one.

Toastmasters provides clubs with hosting for sites like this so it is easy to find out where they meet and to ask questions. In a public club like the one in this example you can just show up at a meeting and they will welcome you. A corporate club will often be just for employees so unless you work for the company that hosts the club you probably will have to look elsewhere. But there are a ton of clubs and most would love to have new members.

At the Python presentation people wanted to look at my PythonDBAGraphs source code. It is on GitHub here: PythonDBAGraphs. This is my largest example of Python code that an Oracle DBA might write. I think that the Oracle community may find PythonDBAGraphs more useful as an example than as a practical application. I use it every day for my work so it has value but it is more command line and less finished than a product that you would buy. Still, it shows how to use Python with Oracle databases and how to graph things using Python. And, it is a fairly simple yet still useful example of Python code.

The README.md has a lot of these details but I thought I would point people to the source files that might be most helpful to them as examples.

db.py has the Oracle database routines using the cx_Oracle module.

myplot.py has the graphing routines using the Matplotlib module.

util.py has some general functions that read or write from files, prompt for input from the command line, or process command line arguments.

The rest of the files are each one graph. I use these in the same way that I use the command line sqlplus scripts that I use for performance tuning. For each graph there is some code for stitching together a SQL query to get information from DBA_HIST or V$ views. Then each one calls routines in db.py, myplot.py, and util.py to do the rest. I tried to put as much logic as possible in db.py, myplot.py, and util.py so that it would be easy to quickly create a new graph.

onewait.py is an example of a single graph.

A lot of this information is in other blog posts but I thought I would put it here based on the questions that I got from doing the Python talk at RMOUG Training Days.

Anyway, I wanted to publish the PowerPoint files and give these two follow ups based on the questions that I got after each talk.

Bobby

Well, it is early Wednesday morning here at the Westin hotel in Denver where the RMOUG Training Days conference is being held. I can’t sleep anyway so I thought I would write-up some of my impressions of yesterday’s presentations.

I appreciate all the effort people put in making their presentations. Since I have done Toastmasters I’ve learned to appreciate more what goes into being an effective speaker. But, the nature of my work is that I have to be critical of everything people say about technology. Maybe I should say “I have to think critically” instead of “be critical”. The problem with the type of work we do is that it involves a lot of money and that inevitably obscures the truth about the technical details of how things work. So, I want to just sit back and applaud but my technical side wants to tear apart every detail.

A nice perk of being a RMOUG presenter is that I got to attend the pre-conference workshops for free as well as the rest of the talks. In past conferences that I have spoken at that was not the case. So, I went to a four-hour Snowflake workshop. I have read a fair amount on Snowflake so much that the speaker presented was familiar. I wonder how people who had no Snowflake background perceived the talk? Being a nuts and bolts Oracle person I would have liked to dig in more to Snowflake internals and discuss its limitations. Surely any tool has things it does better and things that it does not do so well because of the choices that the developers made in its design. I’m interested in how Snowflake automatically partitions data across files on S3 and caches data in SSD and RAM at the compute level. At least, that is what the information on the web site suggests. But with cloud computing it seems that people frown upon looking under the covers. The goal is to spin up new systems quickly and Snowflake is fantastic at that. Also, it seems to get great performance with little effort. No tuning required! Anyway, it was a good presentation but didn’t get into nuts and bolts tuning and limitations which I would have liked to see.

I spent the rest of the day attending hour-long presentations on various topics. AWS offered a 3 hour session on setting up Oracle on RDS but since I’ve played with RDS at work I decided to skip it. Instead I went to mostly cloud and Devops sessions. I accidentally went to an Oracle performance session which was amusing. It was about tuning table scans in the cloud. The speaker claimed that in Oracle’s cloud you get sub-millisecond I/O which raised a bunch of questions in my mind. But the session was more about using Oracle database features to speed up a data warehouse query. It was fun but not what I expected.

I was really surprised by the Devops sessions. Apparently Oracle has some free Devops tools in their cloud that you can use for on premise work. My office is working with a variety of similar tools already so it is not something we would likely use. But it could be helpful to someone who doesn’t want to install the tools yourself. I’m hopeful that today’s Devops session(s) will fill in more details about how people are using Devlops with databases. I’m mostly interested in how to work with large amounts of data in Devops. It’s easy to store PL/SQL code in Git for versioning and push it out with Flywaydb or something like it. It is hard to make changes to large tables and have a good backout. Data seems to be Devops’s Achilles heel and I haven’t seen something that handles it well. I would love to hear about companies that have had success handling data changes with Devops tools.

Well, I’ve had one cup of coffee and Starbucks doesn’t open for another half hour but this is probably enough of a pre-dawn RMOUG data dump. Both of my talks are tomorrow so today is another day as a spectator. Likely it will be another day of cloud and Devops but I might sneak an Oracle performance talk in for one session.

Bobby

We had an outage on an important application last Thursday. A particular SQL statement locked up our database with library cache: mutex X waits. I worked with Oracle support to find a bug that caused the issue and we came up with a good workaround. The bug caused a bunch of shared cursor entries. So, I wanted to run a test on a test database to recreate the excess shared cursor entries. I wanted to run the SQL query that caused the outage a bunch of times. Also, we embed the SQL query inside a PL/SQL procedure so I wanted to run the query by calling the procedure. So, I needed to come up with a bunch of calls to the procedure using realistic data as a test script. This blog post is about the decision I had to make about creating the test script. Would I use SQL or Python to quickly hack together my test script? I thought it would be interesting to write about my choice because I am working on my Python for the Oracle DBA talk that encourages Oracle DBAs to learn Python. In this situation I turned to SQL instead of Python so what does that say about the value of Python for Oracle DBAs?

Let me lay out the problem that I needed to solve. Note that I was trying to get this done quickly and not spend a lot of time coming up with the perfect way to do it. I had over 6000 sets of bind variable values that the problem query has used in the past. I used my bind2.sql script to get some sample bind variable values for the problem query. The output of bind2.sql was in this format:

2017-11-27 15:08:56 :B1 1
2017-11-27 15:08:56 :B2 ABC
2017-11-27 15:08:56 :B3 JAFSDFSF
2017-11-27 15:08:56 :B4 345
2017-11-27 15:08:56 :B5 6345
2017-11-27 15:08:56 :B6 10456775
2017-11-27 15:08:56 :B7 34563465
2017-11-27 15:08:56 :B8 433
2017-11-27 15:09:58 :B1 1
2017-11-27 15:09:58 :B2 JUL
2017-11-27 15:09:58 :B3 KSFJSDJF
2017-11-27 15:09:58 :B4 234
2017-11-27 15:09:58 :B5 234253
2017-11-27 15:09:58 :B6 245
2017-11-27 15:09:58 :B7 66546
2017-11-27 15:09:58 :B8 657576
2017-11-27 15:10:12 :B1 1
2017-11-27 15:10:12 :B2 NULL
2017-11-27 15:10:12 :B3 NULL
2017-11-27 15:10:12 :B4 45646
2017-11-27 15:10:12 :B5 43
2017-11-27 15:10:12 :B6 3477
2017-11-27 15:10:12 :B7 6446
2017-11-27 15:10:12 :B8 474747

I needed to convert it to look like this:

exec myproc(34563465,10456775,345,433,6345,'JAFSDFSF','ABC',1,rc);
exec myproc(66546,245,234,657576,234253,'KSFJSDJF','JUL',1,rc);
exec myproc(6446,3477,45646,474747,43,'NULL','NULL',1,rc);

I gave myself maybe a minute or two to decide between using SQL or Python. I choose SQL. All I did was insert the data into a table and then manipulate it using SQL statements. Note that the order of the arguments in the procedure call is not the same as the order of the bind variable numbers. Also, some are character and some are number types.

Here is the SQL that I used:

drop table bindvars;

create table bindvars
(datetime varchar2(20),
 varname varchar2(2),
 varvalue varchar2(40));

insert into bindvars values ('2017-11-27 15:08:56','B1','1');
insert into bindvars values ('2017-11-27 15:08:56','B2','ABC');
insert into bindvars values ('2017-11-27 15:08:56','B3','JAFSDFSF');
insert into bindvars values ('2017-11-27 15:08:56','B4','345');
insert into bindvars values ('2017-11-27 15:08:56','B5','6345');
insert into bindvars values ('2017-11-27 15:08:56','B6','10456775');
insert into bindvars values ('2017-11-27 15:08:56','B7','34563465');
insert into bindvars values ('2017-11-27 15:08:56','B8','433');
insert into bindvars values ('2017-11-27 15:09:58','B1','1');
insert into bindvars values ('2017-11-27 15:09:58','B2','JUL');
insert into bindvars values ('2017-11-27 15:09:58','B3','KSFJSDJF');
insert into bindvars values ('2017-11-27 15:09:58','B4','234');
insert into bindvars values ('2017-11-27 15:09:58','B5','234253');
insert into bindvars values ('2017-11-27 15:09:58','B6','245');
insert into bindvars values ('2017-11-27 15:09:58','B7','66546');
insert into bindvars values ('2017-11-27 15:09:58','B8','657576');
insert into bindvars values ('2017-11-27 15:10:12','B1','1');
insert into bindvars values ('2017-11-27 15:10:12','B2','NULL');
insert into bindvars values ('2017-11-27 15:10:12','B3','NULL');
insert into bindvars values ('2017-11-27 15:10:12','B4','45646');
insert into bindvars values ('2017-11-27 15:10:12','B5','43');
insert into bindvars values ('2017-11-27 15:10:12','B6','3477');
insert into bindvars values ('2017-11-27 15:10:12','B7','6446');
insert into bindvars values ('2017-11-27 15:10:12','B8','474747');

commit;

drop table bindvars2;

create table bindvars2 as
select 
b1.varvalue b1,
b2.varvalue b2,
b3.varvalue b3,
b4.varvalue b4,
b5.varvalue b5,
b6.varvalue b6,
b7.varvalue b7,
b8.varvalue b8
from 
bindvars b1,
bindvars b2,
bindvars b3,
bindvars b4,
bindvars b5,
bindvars b6,
bindvars b7,
bindvars b8
where
b1.datetime = b2.datetime and
b1.datetime = b3.datetime and
b1.datetime = b4.datetime and
b1.datetime = b5.datetime and
b1.datetime = b6.datetime and
b1.datetime = b7.datetime and
b1.datetime = b8.datetime and
b1.varname = 'B1' and
b2.varname = 'B2' and
b3.varname = 'B3' and
b4.varname = 'B4' and
b5.varname = 'B5' and
b6.varname = 'B6' and
b7.varname = 'B7' and
b8.varname = 'B8';

select 'exec myproc('||
B7||','||
B6||','||
B4||','||
B8||','||
B5||','''||
B3||''','''||
B2||''','||
B1||',rc);'
from bindvars2;

I hacked the insert statements together with my Textpad text editor and then loaded the rows into a little table. Then I built a new table which combines the 8 rows for each call into a single row with a column for each bind variable. Finally I queried the second table generating the procedure calls with single quotes, commas and other characters all in the right place.

Now that the rush is past and my testing is done I thought I would hack together a quick Python script to do the same thing. If I had chosen Python how would have I done it without spending a lot of time making it optimal? Here is what I came up with:

Instead of insert statements I pulled the data into a multi-line string constant. Then I split it into a list of strings with each string representing a line. Then I split each line into space delimited strings so each line would have date,time,bind variable name, bind variable value. Finally I looped through each set of 8 lines extracting the bind variable values and then printing the bind variables in the correct order and format.

These are two quickly hacked together solutions. I think the key point is how I stored the data. With SQL I used tables. With Python I used lists. I’m not sure which I like better in this case. I’ve been doing SQL longer but Python wasn’t really harder. I guess my decision under pressure to use SQL shows that I still have more comfort with the SQL way of doing things, but my after the fact Python hacking shows that the Python solution was not any harder. FWIW.

Bobby

The deadline for early registration for RMOUG Training Days 2018 is rapidly approaching. The deadline is January 12. The early registration fee is $385 for RMOUG members and $450 for non-members. There is a packed agenda over the three-day event. The hotel costs are reasonable at $159/night which is very good compared to the hotel prices at the vendor conferences in San Francisco. RMOUG is reasonably priced and high quality training. With all of the change going on with cloud computing and some of the database systems that are competing with Oracle now I am looking forward to hearing from other people about how they are adapting in this changing climate.

I am giving two talks which are both about personal development for DBAs. One is about whether a DBA should learn the Python programming language. The other is about whether DBAs could benefit from communication and leadership training through Toastmasters. Here are the dates and times for my two talks:

Toastmasters for the Oracle DBA
Thursday, February 22
Session 12, 1:30 pm – 2:30 pm

Python for the Oracle DBA
Thursday, February 22
Session 14, 4:00 pm – 5:00 pm

As things change it makes sense for DBAs to continue to develop themselves and I think that my talks and the conference in general will help us to move forward by preparing us to meet the challenges that the future will bring. I hope to see you in Denver and don’t forget to register by January 12.

B0bby