recursive-query

I came across this CTE solution for concatenating row elements and I thought it's brilliant and I realized how powerful CTEs can be. However, in order to use such a tool effectively I need to know how it works internally to build that mental image which is essential for beginners, like me, to use it in different scenarios. So I tried to slow motion the process of the above snippet and here is the code USE [NORTHWIND] GO /****** Object: Table [dbo].[Products2] Script Date: 10/18/2011 08:55:07 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO IF OBJECT_ID('Products2','U') IS NOT NULL DROP

I have a connected set of edges with unique nodes. They are connected using a parent node. Consider the following example code and illustration: CREATE TABLE network ( node integer PRIMARY KEY, parent integer REFERENCES network(node), length numeric NOT NULL ); CREATE INDEX ON network (parent); INSERT INTO network (node, parent, length) VALUES (1, NULL, 1.3), (2, 1, 1.2), (3, 2, 0.9), (4, 3, 1.4), (5, 4, 1.6), (6, 2, 1.5), (7, NULL, 1.0); Visually, two groups of edges can be identified. How can the two groups be identified using PostgreSQL 9.1, and length summed? The expected result is shown:

I'm reading about Spring Security and wonder whether it's possible to use Spring ACL together with hibernate and pagination. The resulting SQL is surely scary but possible to be auto-generated. It's even possible to use hierarchical ACL if the database supports recursive query evaluation . Using a post filter is no solution since it breaks pagination and is an unnecessary overhead compared to ACL filtering inside the database. So I actually have the pieces to build a solution. I want to know whether somebody has already done it. Links: Similar question from 2012 without response link list

PostgreSQL 9.1 Business situation Every month, there is a new batch of accounts given to a specific process. Every batch can be described by month, number of accounts and total balance of accounts. The goal of the process is to recover some of the balance back from customers. Each batch is than tracked separately on a monthly basis (amount recovered on each month since batch was transferred to the process). Goal My goal is to predict what amount will be recovered in the future. Data definition create table vintage_data ( granularity date, /* Month when account entered process*/ distance_in

I have a simple question. Somehow I was unable to find a definitive answer. How much is WITH RECURSIVE syntax optimized in PostgreSQL? By that I mean: is it merely a syntactic sugar for a series of non recursive queries, OR is it more of a single statement that despite its complicated semantics has been optimized as a whole. A follow-up question - just about how much is it possible to optimize this kind of syntax? Of course some concrete data on the matter is most welcome. My experience is that it is indeed very well optimized. Check out the execution plan for your query generated by EXPLAIN

I'm using PostgreSQL 9.1 to query hierarchical tree-structured data, consisting of edges (or elements) with connections to nodes. The data are actually for stream networks, but I've abstracted the problem to simple data types. Consider the example tree table. Each edge has length and area attributes, which are used to determine some useful metrics from the network. CREATE TEMP TABLE tree ( edge text PRIMARY KEY, from_node integer UNIQUE NOT NULL, -- can also act as PK to_node integer REFERENCES tree (from_node), mode character varying(5), -- redundant, but illustrative length numeric NOT NULL,