table_inspector.sql

/*

Table Skew Inspector. Please see http://docs.aws.amazon.com/redshift/latest/dg/c_analyzing-table-design.html
for more information.

Notes:


History:
2015-11-26 meyersi created
2016-09-13 chriz-bigdata rewrote to simplify and align with documentation

*/
SELECT SCHEMA schemaname,
       "table" tablename,
       table_id tableid,
       size size_in_mb,
       CASE
         WHEN diststyle NOT IN ('EVEN','ALL') THEN 1
         ELSE 0
       END has_dist_key,
       CASE
         WHEN sortkey1 IS NOT NULL THEN 1
         ELSE 0
       END has_sort_key,
       CASE
         WHEN encoded = 'Y' THEN 1
         ELSE 0
       END has_col_encoding,
       ROUND(100*CAST(max_blocks_per_slice - min_blocks_per_slice AS FLOAT) / GREATEST(NVL (min_blocks_per_slice,0)::int,1),2) ratio_skew_across_slices,
       ROUND(CAST(100*dist_slice AS FLOAT) /(SELECT COUNT(DISTINCT slice) FROM stv_slices),2) pct_slices_populated
FROM svv_table_info ti
  JOIN (SELECT tbl,
               MIN(c) min_blocks_per_slice,
               MAX(c) max_blocks_per_slice,
               COUNT(DISTINCT slice) dist_slice
        FROM (SELECT b.tbl,
                     b.slice,
                     COUNT(*) AS c
              FROM STV_BLOCKLIST b
              GROUP BY b.tbl,
                       b.slice)
        WHERE tbl IN (SELECT table_id FROM svv_table_info)
        GROUP BY tbl) iq ON iq.tbl = ti.table_id
ORDER BY SCHEMA, "table";