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All queries to reproduce the technique from my blog post https://torsten.io/stdout/expanding-json-arrays-to-rows
-- Related blog post to this Gist:
-- https://torsten.io/stdout/expanding-json-arrays-to-rows
-- Run these commands on a interactive RedShift session:
CREATE TEMP TABLE clusters AS (
SELECT 1 AS id, '[1, 2]' AS node_sizes UNION ALL
SELECT 2 AS id, '[5, 1, 3]' AS node_sizes UNION ALL
SELECT 3 AS id, '[2]' AS node_sizes
);
-- This is just a temp table to leave no trace after the session
-- In practice I am using a `CREATE VIEW` and more rows.
CREATE TEMP TABLE seq_0_to_100 AS (
SELECT 0 AS i UNION ALL
SELECT 1 UNION ALL
SELECT 2 UNION ALL
SELECT 3 UNION ALL
SELECT 4 UNION ALL
SELECT 5
-- I am stopping here, you could easily generate this as a VIEW with 100+ real rows...
);
-- To see the intermediate relation:
SELECT id, JSON_EXTRACT_ARRAY_ELEMENT_TEXT(node_sizes, seq.i) AS size
FROM clusters, seq_0_to_100 AS seq
WHERE seq.i < JSON_ARRAY_LENGTH(node_sizes)
ORDER BY 1, 2;
-- To fetch the maximum size:
WITH exploded_array AS (
SELECT id, JSON_EXTRACT_ARRAY_ELEMENT_TEXT(node_sizes, seq.i) AS size
FROM clusters, seq_0_to_100 AS seq
WHERE seq.i < JSON_ARRAY_LENGTH(node_sizes)
)
SELECT max(size)
FROM exploded_array;
@urjitbhatia
urjitbhatia commented Jan 20, 2017 edited

Thanks for this amazing hack 👍

Btw, you can create the sequence table with less manual work:

SELECT ROW_NUMBER() OVER (ORDER BY TRUE)::INTEGER- 1 as seq into seq_0_to_5000
FROM <table.with.at-least.5000.rows> LIMIT 5000;
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