[Solved] Consider this recursive CTE:WITH RECURSIVE path(node) AS (SELECT 1 UNION ALL SELECT node + 1 FROM path WHERE node What is wrong if this query runs forever without stopping? | PostgreSQL

PostgreSQL - Common Table Expressions

Consider this recursive CTE:

WITH RECURSIVE path(node) AS (SELECT 1 UNION ALL SELECT node + 1 FROM path WHERE node < 3) SELECT * FROM path;

What is wrong if this query runs forever without stopping?

ANot selecting from the CTE in the final SELECT

BMissing a proper termination condition in the recursive part

CUsing UNION instead of UNION ALL

DIncorrect anchor query syntax

Step-by-Step Solution

Solution:

Step 1: Analyze the recursive condition
The recursive part adds 1 to node while node < 3, but due to UNION ALL accumulating duplicates of rows satisfying the condition, recursion continues indefinitely.
Step 2: Identify why it loops infinitely
If the termination condition is incorrect or not reached, recursion never stops. Here, the condition is present but ineffective against duplicates, causing infinite loop.
Final Answer:
Missing a proper termination condition in the recursive part -> Option B
Quick Check:
Infinite recursion = no stop condition [OK]

Quick Trick: Check recursive WHERE clause stops recursion [OK]

Common Mistakes:

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Consider this recursive CTE: