Enhanced compatibility features v17

EDB Postgres Advanced Server includes extended functionality that provides compatibility for syntax supported by Oracle applications. See Database compatibility for Oracle developers for additional information about the compatibility features supported by EDB Postgres Advanced Server.

Enabling compatibility features

You can install EDB Postgres Advanced Server in several ways to enable compatibility features:

• Before initializing your cluster, use the INITDBOPTS variable in the EDB Postgres Advanced Server service configuration file to specify --redwood-like.
• Include the --redwood-like parameter when using initdb to initialize your cluster.

See Configuration parameters compatible with Oracle databases and Managing an EDB Postgres Advanced Server installation for more information about the installation options supported by the EDB Postgres Advanced Server installers.

Stored procedural language

EDB Postgres Advanced Server supports a highly productive procedural language that allows you to write custom procedures, functions, triggers, and packages. This procedural language:

• Complements the SQL language and built-in packages.
• Provides a seamless development and testing environment.
• Allows you to create reusable code.

See Stored procedural language for more information.

Optimizer hints

When you invoke a DELETE, INSERT, SELECT, or UPDATE command, the server generates a set of execution plans. After analyzing those execution plans, the server selects a plan that generally returns the result set in the least amount of time. The server's choice of plan depends on several factors:

• The estimated execution cost of data-handling operations
• Parameter values assigned in the Query Tuning section of the postgresql.conf file
• Column statistics that are gathered by the ANALYZE command

As a rule, the query planner selects the least expensive plan. You can use an optimizer hint to influence the server as it selects a query plan. An optimizer hint is one or more directives embedded in a comment-like syntax that immediately follows a DELETE, INSERT, SELECT, or UPDATE command. Keywords in the comment instruct the server to use or avoid a specific plan when producing the result set. See Optimizer hints for more information.

Data dictionary views

EDB Postgres Advanced Server includes a set of views that provide information about database objects in a manner compatible with the Oracle data dictionary views. See Database compatibility for Oracle developers: catalog views for detailed information about the views available with EDB Postgres Advanced Server.

dblink_ora

dblink_ora provides an OCI-based database link that allows you to SELECT, INSERT, UPDATE, or DELETE data stored on an Oracle system from EDB Postgres Advanced Server. See dblink_ora for detailed information about using dblink_ora and the supported functions and procedures.

Profile management

EDB Postgres Advanced Server supports compatible SQL syntax for profile management. Profile management commands allow a database superuser to create and manage named profiles. A profile is a named set of attributes that allow you to easily manage a group of roles that share comparable authentication requirements. Each profile defines rules for password management that augment password and md5 authentication. The rules in a profile can:

• Count failed login attempts
• Lock an account due to excessive failed login attempts
• Mark a password for expiration
• Define a grace period after a password expiration
• Define rules for password complexity
• Define rules that limit password reuse

After creating the profile, you can associate the profile with one or more users. If password requirements change, you can modify the profile to apply the new requirements to each user that's associated with that profile.

When a user connects to the server, the server enforces the profile that's associated with their login role.

Profiles are shared by all databases in a cluster, but each cluster can have multiple profiles. A single user with access to multiple databases uses the same profile when connecting to each database in the cluster.

See Profile management for information about using profile management commands.

Built-in packages

EDB Postgres Advanced Server supports a number of built-in packages that provide compatibility with Oracle procedures and functions.

See Built-in packages for detailed information about the procedures and functions available in each package.

Open Client Library

The Open Client Library provides application interoperability with the Oracle Call Interface. An application that was formerly “locked in” can now work with either an EDB Postgres Advanced Server or an Oracle database with minimal to no changes to the application code. The EDB implementation of the Open Client Library is written in C.

The following diagram compares the Open Client Library and Oracle Call Interface application stacks.

For detailed information about the functions supported by the Open Client Library, see EDB OCL Connector.

Utilities

For detailed information about the compatible syntax supported by these utilities, see Tools, utilities, and components.

EDB*Plus

EDB*Plus is a utility program that provides a command line user interface to the EDB Postgres Advanced Server that's familiar to Oracle developers and users. EDB*Plus accepts SQL commands, SPL anonymous blocks, and EDB*Plus commands.

EDB*Plus allows you to:

• Query certain database objects
• Execute stored procedures
• Format output from SQL commands
• Execute batch scripts
• Execute OS commands
• Record output

See EDB*Plus for more information.

EDB*Loader

EDB*Loader is a high-performance bulk data loader that provides an interface compatible with Oracle databases for EDB Postgres Advanced Server. The EDB*Loader command line utility loads data from an input source, typically a file, into one or more tables using a subset of the parameters offered by Oracle SQL*Loader.

EDB*Loader features include:

• Support for the Oracle SQL*Loader data loading methods—conventional path load, direct path load, and parallel direct path load
• Oracle SQL*Loader-compatible syntax for control file directives
• Input data with delimiter-separated or fixed-width fields
• Bad file for collecting rejected records
• Loading of multiple target tables
• Discard file for collecting records that don't meet the selection criteria of any target table
• Data loading from standard input and remote loading

See Loading bulk data for information.

EDB*Wrap

The EDB*Wrap utility protects proprietary source code and programs (functions, stored procedures, triggers, and packages) from unauthorized scrutiny. The EDB*Wrap program translates a file that contains SPL or PL/pgSQL source code (the plaintext) into a file that contains the same code in a form that's nearly impossible to read. Once you have the obfuscated form of the code, you can send that code to EDB Postgres Advanced Server, which stores those programs in obfuscated form. While EDB*Wrap does obscure code, table definitions are still exposed.

Everything you wrap is stored in obfuscated form. If you wrap an entire package, the package body source as well as the prototypes contained in the package header and the functions and procedures contained in the package body are stored in obfuscated form.

See Protecting proprietary source code for information.

Dynamic Runtime Instrumentation Tools Architecture (DRITA)

DRITA allows a DBA to query catalog views to determine the wait events that affect the performance of individual sessions or the system as a whole. DRITA records the number of times each event occurs as well as the time spent waiting. You can use this information to diagnose performance problems. DRITA offers this functionality while consuming minimal system resources.

DRITA compares snapshots to evaluate the performance of a system. A snapshot is a saved set of system performance data at a given point in time. A unique ID number identifies each snapshot. You can use snapshot ID numbers with DRITA reporting functions to return system performance statistics.

See Using dynamic resource tuning for information.

ECPGPlus

EDB enhanced ECPG (the PostgreSQL precompiler) to create ECPGPlus. ECPGPlus allows you to include embedded SQL commands in C applications. When you use ECPGPlus to compile an application that contains embedded SQL commands, the SQL code is syntax checked and translated to C.

ECPGPlus supports Pro*C syntax in C programs when connected to an EDB Postgres Advanced Server database. ECPGPlus supports:

• Oracle Dynamic SQL – Method 4 (ODS-M4)
• Pro*C-compatible anonymous blocks
• A CALL statement compatible with Oracle databases

See ECPGPlus for information.

Table partitioning

In a partitioned table, one logically large table is broken into smaller physical pieces. Partitioning can provide several benefits:

• Query performance can be improved dramatically in certain situations, particularly when most of the heavily accessed rows of the table are in a single partition or a small number of partitions. Partitioning allows you to omit the partition column from the front of an index, reducing index size and making it more likely that the heavily used parts of the index fit in memory.
• When a query or update accesses a large percentage of a single partition, performance might improve because the server performs a sequential scan of the partition instead of using an index and random access reads scattered across the whole table.
• If you plan the requirement into the partitioning design, you can implement bulk load or unload by adding or removing partitions. ALTER TABLE is faster than a bulk operation. It also avoids the VACUUM overhead caused by a bulk DELETE.
• You can migrate seldom-used data to less expensive or slower storage media.

Table partitioning is worthwhile only when a table would otherwise be very large. The exact point at which a table benefits from partitioning depends on the application. A good estimation is when the size of the table exceeds the physical memory of the database server.

For information about database compatibility features supported by EDB Postgres Advanced Server, see Table partitioning.