[HACKERS] how to implement selectivity injection in postgresql

SELECT c1, c2, c3, FROM T1, T2, T3 WHERE T1.x = T2.x AND T2.y=T3.y AND T1.x = ? selectivity 0.1 AND T2.y ? selectivity 0.5 AND T3.z = ? selectivity 0.2 AND T3.w = ? I need to implement Selectivity injection as shown in above query in PostgreSQL

[HACKERS] how to skip building certain paths in path tree

How do I modify PostgreSQL 9.3 source to skip certain join combinations (skip building certain paths in path tree) by checking some condition

[HACKERS] how to find the order of joins from Explain command XML plan output in PostgreSQL

EXPLAIN (format XML) command in PostgreSQL9.3.4 gives the plan chosen by the optimizer in XML format. In my program, I have to extract certain data about optimizer plan from this XML output. I am using *LibXML2* library for parsing the XML. I had successfully extracted information about which

[HACKERS] how to find the order of joins from Explain command XML plan output in PostgreSQL9.3.4

EXPLAIN (format XML) query command in PostgreSQL9.3.4 gives the plan chosen by the optimizer in XML format. In my program, I have to extract certain data about optimizer plan from this XML output. I am using *LibXML2* library for parsing the XML. I had successfully extracted information

[HACKERS] Estimating selectivity of predicates involving string pattern matching

I recently upgraded my machine from PostgreSQL8.3 to PostgreSQL9.3.4. After upgrade, when I ran TPC-H queries for performance testing, I could see drastic change in timings. Especially TPC-H query 5 which was taking 4 minutes to execute in pgsql8.3, took just 15 seconds in postgresql9.3.4. I think

[HACKERS] loading .so file at run time

I am working with Postgresql 9.3.4 source using eclipse IDE in ubuntu 14.04. I have a library file abc.so to be loaded at run time when postgresql server starts. When I run the server with -D /home/rajmohan/projects/TPCH_database as argument in run configuration, I could see LOG message abc.so

[HACKERS] unable to attach client process to postgresql server using gdb

hi, I am working with PostgreSQL 9.3.4 source using Eclipse IDE in ubuntu 14.04. I am facing a problem in attaching client process to postgresql server using gdb to debug. When I start the postmaster then I connect to it from client on a terminal. It works fine. Queries get responses. When I

[HACKERS] is there a hook by which we can modify input query before postgresql builds raw parse tree

Hi, I want to know is there a way to use a hook to modify the input query before Postgresql parses and builds the parse tree for the query.

[HACKERS] hooks not working in postgresql 9.3 (building from source)

hi, I need to use the hook feature of planner in postgresql 9.3 to perform a task. I am building postgresql from source. To start with, I wanted to know how to create a hook and attach that shared libray to postgresql. Hence i tried the examples given in

[HACKERS] Planner hints in Postgresql

I am implementing Planner hints in Postgresql to force the optimizer to select a particular plan for a query on request from sql input. I am having trouble in modifying the planner code. I want to create a path node of hint plan and make it the plan to be used by executor. How do I enforce this ?