Code Based Access Control for Definer’s Rights and Invoker’s Rights Oracle Database 12C release 2 (12.2)

In Oracle 12C it’s possible to assign a role to a code procedure/function/package

GRANT role_name TO PROCEDURE|FUNCTION|PACKAGE code_name;

This kind of grant can be executed only by following user:

  • SYS
  • user with GRANT ANY ROLE privilege
  • user who own code and was granted the role with ADMIN OPTION
  • user who own code and was granted the role with DELEGATE OPTION

Top three options are commonly know. New option is DELEGATE OPTION. It enables to grant a role to procedure|function|package and nothing more.

Once the role is granted to a code the role is always enabled no matter if the code is created with PRAGMA AUTHID_USER or PRAGMA DEFINER and no matter if owner of the code calls it or other user.

Continue reading

NO_EXPAND USE_CONCAT hints

This article focus on two hints:

USE_CONCAT -  The USE_CONCAT hint forces combined OR conditions in the WHERE clause of a query to be transformed into a compound query using the UNION ALL set operator. Generally, this transformation occurs only if the cost of the query using the concatenations is cheaper than the cost without them.

NO_EXPAND - The NO_EXPAND hint prevents the cost-based optimizer from considering OR-expansion for queries having OR conditions or IN-lists in the WHERE clause. Usually, the optimizer considers using OR expansion and uses this method if it decides that the cost is lower than not using it.

NO_EXPAND can be forced by alter session for all statements

ALTER SESSION SET "_no_or_expansion" = TRUE;

Continue reading

Install Fedora 26

This article presents how to install Fedora 26 – Live Workstation version.

I assume you have already downloaded Fedora 26 64 bit Live Workstation(about 1,3 G) and you know how to use VirtualBox 64 bit(100M). Create virtual machine with default settings for Linux Fedora 64 bit. 2CPU, 2GB ram and 64G(includes extra space for Oracle installations) for disk is enough plus increase video memory to 128M. Rest of options you can keep default.

Continue reading

Enhanced Partitioning Oracle Database 12C release 2 (12.2)

This article describes new options available in Oracle Database Release 12.2 for partitioning:

  • extensions for list partitioning
    • automatic list partitioned table
    • multi-column list partitioned table
  • read-only partitions and subpartitions
  • filtering maintenance operations
  • creating a table for exchange with a partitioned table
  • online converting non-partitioned table to a partitioned table
  • online split partition and subpartition

Continue reading

Create drop database link in another schema Oracle

Unfortunately in Oracle you can’t create or drop database link in another schema. It’s very frustrating. Simple solution is to create anonymous block which will first create dummy function in another schema and then reuse it to create or drop an object(in our case database link).

Of course it can be reused to do other types of object as well.

Continue reading