Database Technologies

In series of blogging about new features coming in PostgreSQL 9.3, I thought to blog about the server side language improvements in PostgreSQL. Lets see whats coming in server side language. As PostgreSQL user, you know, PostgreSQL supports multiple server side language. In 9.3, there are some interesting features are coming. Lets look at the new improvements about to come. 1. SPI access to number of rows processed by COPY command. This is more like new feature which is introduced in 9.3. Before 9.3, this feature was missing. i.e if user uses COPY command inside the plperl/plpython functions, then there was no way inside the procedure to trace the number of rows processed by COPY. However in 9.3, this limitation is no more exists with procedural language. There are many languages supported in PostgreSQL, However I chose to test this with mostly used language plperl and plpython. Below are some snapshot pre-9.3 and in 9.3. Lets check with plperl. Following is a plperl function w...

Long long time. I haven't blogged at all. So, I have decided whenever I get chance I will blog about the cool things going in Database Technology market. I have lot of topics to share. Some got lost in air. Some I retained in mind. Before I lost more. I decided to continue from PostgreSQL 9.3 features and accordingly will go towards about new things as it starts to popup. PostgreSQL users must have heard about release of PostgreSQL 9.3 and they must have started testing PostgreSQL 9.3. In today series, I am going to blog about client application improvements done in PostgreSQL 9.3. Lets take it one by one. 1. New binary/command pg_isready.  PostgreSQL 9.3 is coming with new binary called pg_isready. this command helps user to know the status of server/PostgreSQL cluster. Before 9.3, user used to have their own tool/script to check the status of PostgreSQL, for that they used execute some random SQL like "SELECT 1" and if the status is successful, PostgreSQL is ...

In PostgreSQL 9.2, community has added a function pg_xlog_location_diff(), which is very useful for finding the difference between two xlog location in bytes and also useful for monitoring replication. Detail of this function is given in following link: http://www.postgresql.org/docs/9.2/static/functions-admin.html#FUNCTIONS-ADMIN-BACKUP However this function is not available for users of PostgreSQL/PPAS 9.0/9.1 users. So, I thought to write same function plpgsql so, that users can take benefit of same in 9.0/9.1. Before using formula and developing function, lets understand what is xlog and offset. Let's consider user has used function pg_current_xlog_location() function and he gets following information: worktest=# select pg_current_xlog_location(); pg_current_xlog_location -------------------------- 1/D1012B80 (1 row) In above, first field before forward slash is the hexadecimal value of logical xlog file and second field i.e. D1012B80 is hexadecimal offset inside ...

Good News Postgres Plus Advanced Server Beta Version is now availabale, which has all the new feature of PostgreSQL 9.2, and it also has new features which are specific to Advanced Server. I will cover/explain New features of PostgreSQL 9.2 later as per release Notes. However, the following link covers major features of PostgreSQL 9.2 and can be taken as reference. http://wiki.postgresql.org/wiki/What's_new_in_PostgreSQL_9.2 In this Blog, I am going to cover only specific features of Advanced Server 9.2 Core. Which are: 1. INSERT APPEN HINT in PPAS 9.2 PPAS 9.2, now supports INSERT append hint. This is a very interesting feature and it is very useful for users who frequently delete records in Bulk and do bulk of INSERTs. This hint can provide some benefits in INSERTs. This hint makes PPAS not use Free Space Map and Append the rows at the end of relation(table). Its usage is given below: INSERT /*+append*/ INTO tab21115 VALUES(1,'abc',sysdate); 2. Procedure Called l...

PostgreSQL has some useful functions which can be use to know about the privilege of a user on a particular Database object. Those functions is available in following link: http://www.postgresql.org/docs/9.1/static/functions-info.html Functions has_*_privilege in PostgreSQL/PPAS is good to know about privilege a user has on one database objects and these function returns boolean value true or false. Since, DBAs/Users are interested in listing objects and privileges of a Database User and currently PostgreSQL doesn't have a view, which DBA can use to list users privileges on objects for a particular database. Therefore, I thought about making some functions, which can be used to list users privileges, based on what is available in PostgreSQL/PPAS 9.1. These are basic functions and can be expanded, as per need, to show more privileges like WITH GRANT OPTION. Following are functions which can use to get the privileges of a particular user: 1. Function for table privileges: C...

PostgreSQL has pg_stat_activity view which can be use to get the session details. This view gives following information: 1. datid: database OID 2. datname: database name 3. procpid: process ID 4. usesysid: user OID 5. usename: user name 6. application_name: application name 7. client_addr: client's address 8. client_hostname: host name (if available) 9. client_port: Clients port number 10. backend_start: time at which the server process started 11. xact_start: time at which current transaction started 12: query_start: time at which current query began execution started 13: waiting: process's waiting status 14. current_query: text of the current query. Above is good for monitoring sessions in postgresql. However, suppose user wants to know about percentage of CPU & Memory used by a particular session/user, then he can get this information by using plperlu function. To Create the pleperlu function, user needs to have plperlu language installed in DB. For creating the p...

This is also one type of thing in which people are very interested. How to create probes other than PEM inbuilt probe? And how to create alert based on probe? Well answer is simple. Understand what probe is in PEM and then understand PEM Data detail. Probe in PEM requires following: 1. SQL Code which can be use to gathering data by pemagent. 2. Table in pemdata schema, which will be use for storing Current status/data of SQL. 3. History table (specially in pemhistory schema) where all history data will reside. Suppose user wants to monitor the Slony Replication using PEM (since, PEM doesn't have slony replication moniotring), so user can do following: 1. SQL Code which can be use for slony replication monitoring. We know that slony replication monitoring can be done using view sl_status of slony. So, user can create a SQL Code as given below for replication. select '_test_slony' as schema_name, st_origin,st_received, st_lag_num_events , st_lag_time from _test_slony...