New READ Object Privilege in 12cR1

In writing a blog post about:
Creating a Read Only Database User Account in an Oracle Database

It came to my attend of the new “READ” object privilege, which is a New Feature in 12.1.0.2:
Changes in Oracle Database 12c Release 1 (12.1.0.2)
READ and SELECT Object Privileges

The “SELECT” object privilege in addition to querying the table, allow the user to:
LOCK TABLE table_name (more...)

Creating a Read Only Database User Account in an Oracle Database

It can be quite common to create a “Read Only” database user account in an Oracle database.  To do this is pretty simple using the principle of least privilege:

CREATE USER READ_ONLY IDENTIFIED BY "password";
GRANT CREATE SESSION TO READ_ONLY;

Expected output:

SQL> CREATE USER READ_ONLY IDENTIFIED BY "password";

User created.

SQL> GRANT CREATE SESSION TO READ_ONLY;

Grant succeeded.

SQL>

To see specific tables for a schema:

SET HEADING OFF
SET PAGES  (more...)

Microservices and Updating Data Bound Context on Oracle Cloud with Application Container and Event Hub (plus DBaaS and MongoDB)–Part Two

This article describes – in two installments – how events are used to communicate a change in a data record owned by the Customer microservice to consumers such as the Order microservice that has some details about the modified customer in its bound context. The first installment described the implementation of the Customer microservice – using MongoDB for its private data store and producing events to Event Hub cloud service to inform other microservices about (more...)

Easy(lazy) way to check which programs have properly configured FetchSize

select 
   s.module
  ,ceil(max(s.rows_processed/s.fetches)) rows_per_fetch
from v$sql s
where 
    s.rows_processed>100
and s.executions    >1
and s.fetches       >1
and s.module is not null
and s.command_type  = 3    -- SELECTs only
and s.program_id    = 0    -- do not account recursive queries from stored procs
and s.parsing_schema_id!=0 -- <> SYS
group by s.module
order by rows_per_fetch desc nulls last
/

Comparing queries…

How do you compare a rewritten query to its original version? Most of the time I just run a MINUS operation on the original and new query. Actually I execute two. Old query (A) MINUS New query (B) and vice versa (B) MINUS (A). Both should result in no rows. That way I thought I had proven that the resultsets for both queries are equal.
But there is a flaw in this assumption.

What if (more...)

KSQL: Streaming SQL for Apache Kafka

KSQL: Streaming SQL for Apache Kafka

Few weeks back, while I was enjoying my holidays in the south of Italy, I started receiving notifications about an imminent announcement by Confluent. Reading the highlights almost (...I said almost) made me willing to go immediately back to work and check all the details about it.
The announcement regarded KSQL: a streaming SQL engine for Apache Kafka!


Identifying Conditional Navigation Content References

As PeopleSoft customers upgrade to Fluid-enabled applications, it is quite common to start with Fluid disabled, and then implement Fluid behavior post go-live. It is all about change management and an organization's ability to digest change. Even though Oracle has set retirement dates for certain Classic components, with the first wave retiring December 31, 2017, all Classic functionality is still supposed to be present and available. But if you have opened a recent PeopleSoft image (more...)

ODC Appreciation Day: EMP #ThanksODC

Here is my very short entry for the Oracle Developer Community Appreciation Day 2017.

Very often I use the good ol' EMP table to demonstrate even the latest features of SQL and PL/SQL.
Everybody seems to know the EMP table, and some even know some of the content off the top of their head (yes, I'm guilty of that too). Whenever I need to write a hierarchical query and am not really sure what which (more...)

Overloaded Indexes (for ODC Appreciation Day)

ODC Appreciation Day is an idea that Tim Hall (aka Oracle-Base) came up with, to show out appreciation for the Oracle Technology Program (OTN)/Oracle Developer Community.

Fig 1 This is an efficient range scan

I want to show my support but rather than mention an Oracle “feature” I particularly like I’d like to mention a “trick” that I (and many others) often employ to help performance. That trick is Overloaded Indexes.

We can all (more...)

ODC Appreciation Day: Collections in SQL

Here’s my contribution to the ODC Appreciation Day.

Overview

Last week I had the privilege to participate in the EOUC Database ACES Share Their Favorite Database Things session at Oracle OpenWorld, so I think that the best topic to write about, as part of the ODC Appreciation Day, is the one I talked about in this session.
My 5-minute presentation was about Collections in SQL.

Collections are very useful in PL/SQL development. This is (more...)

RETURNING INTO – Enhancement Suggestion

The RETURNING INTO clause is one of my favorite features.
It returns data from the rows that have been affected by the DML statement, and as I wrote in this previous post:
For INSERT it returns the after-insert values of the new row’s columns.
For UPDATE it returns the after-update values of the affected rows’ columns.
For DELETE it returns the before-delete values of the affected rows’ columns.

For INSERT there are no before-insert (more...)

Did You Know #22 – Reproduce SQL Issue

During OOW17 a customer ran into a wrong result issue in 11.2.0.4, which is very bad. I diagnosed this and found out that it happens because of bloom filter, so we just disabled that and it was solved. But I still opened an SR so Oracle can find and fix this bug. Wrong results bug … Continue reading Did You Know #22 – Reproduce SQL Issue

Implementing Arc Relationships with Virtual Columns? Or Not?

I wrote a post some time ago about implementing arc relationships using virtual columns.
Recently, Toon Koppelaars wrote a detailed and reasoned comment to that post. Since I admire Toon, getting his point of view on something that I wrote is a privilege for me, regardless if he agrees with me or disagrees (and just to be clear, it’s the latter this time). I think that having a public (and civilized) discussion – this time (more...)

How to group connected elements (or pairs)

I see quite often when developers ask questions about connected components:

Table “MESSAGES” contains fields “SENDER” and “RECIPIENT”, which store clients id.
How to quickly get all groups of clients who are connected even through other clients if the table has X million rows?
So for this table, there should be 4 groups:
  • (1, 2, 4, 8, 16)
  • (3, 6, 12)
  • (5, 10, 20)
  • (7, 14)
  • (9, 18)
SENDERRECIPIENT
12
24
3 (more...)

Ampersand instead of colon for bind variables

I’ve troubleshooted one query today and I was very surprised that bind variables in this query were specified with &ampersand instead of :colon! I have never seen this before and I couldn’t find anything about this in documentation…
Unfortunately SQL*Plus doesn’t support ampersand yet, even if you disable define (“set define off”),
so I’ve tested such behaviour with this code:

set def off serverout on
exec declare s varchar2(1); begin execute immediate 'select  (more...)

Simple regexp to check that string contains word1 and word2 and doesn’t contain word3

with tst as (
  select 'qwe word1 asd ...............' s from dual
  union all
  select 'qwe word1 asd word2 .........' s from dual
  union all
  select 'qwe word1 asd word2 zxc word3' s from dual
  union all
  select 'qwe word2 asd word1 zxc word4' s from dual
)
select
  s
  ,regexp_replace(s, '(word1)|(word2)|(word3)|(.)','`\3') subst
  ,case when regexp_like(regexp_replace(s, '(word1)|(word2)|(word3)|(.)','`\3') , '^`+$') then 'matched' end tst2
from tst
where 1=1
--and regexp_like(regexp_replace(s, '(word1)|(word2)|(word3)|(.)','`\3') , '^`+$')

How To Enable DDL Logging in the Database

If for whatever reason, you are required to log DDL, for example, I need to know why the LAST_DDL_TIME of a table was getting updated, you can do this from Oracle 11g.

To enable:

SQL> show parameter ENABLE_DDL_LOGGING

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------ 
enable_ddl_logging boolean FALSE

SQL> ALTER SYSTEM SET ENABLE_DDL_LOGGING=TRUE;

System altered.

SQL> show parameter ENABLE_DDL_LOGGING

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------ 
enable_ddl_logging boolean TRUE

To disable:

SQL> show parameter ENABLE_DDL_LOGGING

NAME TYPE VALUE
------------------------------------ -----------  (more...)

Optimistic Locking 6: which ORA_ROWSCN?

Continuing my series on using ORA_ROWSCN to achieve optimistic locking, let’s zoom in on ORA_ROWSCN itself. I've been asking myself this question:
  • ORA_ROWSCN can be maintained at the block level or the row level. What is the difference and which one should we use?

The best Oracle technology week ever – Part 1: Helsinki and Stockholm

You remember my last blogpost describing how my #europeTour would be like:
#orclapex Europe tour 

It was a week with as little sleep as possible. Reasons:
 - traveling
 - just was to excited
 - to much party

It all started in Helsinki with the first Oracle APEX day in Finland.
I reached Helsinki with Richard Rieb around 10 o'clock in the evening. It was dark and cold, our taxi driver spoke 5 words to (more...)

Install Cassandra on Fedora

It was quite interesting to discover that DataStax no longer provides the DataStax Community version of Apache Cassandra or the DataStax Distribution of Apache Cassandra. Needless to say, I was quite disappointed because it means folks will get less opportunity to learn how to use Cassandra because it makes it more difficult for beginning developers.

I spent a good hour sorting through what was available and then figuring out the real requirements.

After installing and (more...)