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PostgreSQL Common Utility Queries
# Finding the total size of your biggest tables
SELECT nspname || '.' || relname AS "relation",
pg_size_pretty(pg_relation_size(C.oid)) AS "size"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE nspname NOT IN ('pg_catalog', 'information_schema')
ORDER BY pg_relation_size(C.oid) DESC
LIMIT 20;
# Finding the total size of your biggest tables
SELECT nspname || '.' || relname AS "relation",
pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE nspname NOT IN ('pg_catalog', 'information_schema')
AND C.relkind <> 'i'
AND nspname !~ '^pg_toast'
ORDER BY pg_total_relation_size(C.oid) DESC
LIMIT 20;
# Table & index sizes along which indexes are being scanned and how many tuples are fetched
SELECT
t.tablename,
indexname,
c.reltuples AS num_rows,
pg_size_pretty(pg_relation_size(t.tablename::text)) AS table_size,
pg_size_pretty(pg_relation_size(indexrelname::text)) AS index_size,
CASE WHEN x.is_unique = 1 THEN 'Y'
ELSE 'N'
END AS UNIQUE,
idx_scan AS number_of_scans,
idx_tup_read AS tuples_read,
idx_tup_fetch AS tuples_fetched
FROM pg_tables t
LEFT OUTER JOIN pg_class c ON t.tablename=c.relname
LEFT OUTER JOIN
(SELECT indrelid,
max(CAST(indisunique AS integer)) AS is_unique
FROM pg_index
GROUP BY indrelid) x
ON c.oid = x.indrelid
LEFT OUTER JOIN
( SELECT c.relname AS ctablename, ipg.relname AS indexname, x.indnatts AS number_of_columns, idx_scan, idx_tup_read, idx_tup_fetch,indexrelname FROM pg_index x
JOIN pg_class c ON c.oid = x.indrelid
JOIN pg_class ipg ON ipg.oid = x.indexrelid
JOIN pg_stat_all_indexes psai ON x.indexrelid = psai.indexrelid )
AS foo
ON t.tablename = foo.ctablename
WHERE t.schemaname='public'
ORDER BY 1,2;
# Pull the number of rows, indexes, and some info about those indexes for each table
SELECT
pg_class.relname,
pg_size_pretty(pg_class.reltuples::bigint) AS rows_in_bytes,
pg_class.reltuples AS num_rows,
count(indexname) AS number_of_indexes,
CASE WHEN x.is_unique = 1 THEN 'Y'
ELSE 'N'
END AS UNIQUE,
SUM(case WHEN number_of_columns = 1 THEN 1
ELSE 0
END) AS single_column,
SUM(case WHEN number_of_columns IS NULL THEN 0
WHEN number_of_columns = 1 THEN 0
ELSE 1
END) AS multi_column
FROM pg_namespace
LEFT OUTER JOIN pg_class ON pg_namespace.oid = pg_class.relnamespace
LEFT OUTER JOIN
(SELECT indrelid,
max(CAST(indisunique AS integer)) AS is_unique
FROM pg_index
GROUP BY indrelid) x
ON pg_class.oid = x.indrelid
LEFT OUTER JOIN
( SELECT c.relname AS ctablename, ipg.relname AS indexname, x.indnatts AS number_of_columns FROM pg_index x
JOIN pg_class c ON c.oid = x.indrelid
JOIN pg_class ipg ON ipg.oid = x.indexrelid )
AS foo
ON pg_class.relname = foo.ctablename
WHERE
pg_namespace.nspname='public'
AND pg_class.relkind = 'r'
GROUP BY pg_class.relname, pg_class.reltuples, x.is_unique
ORDER BY 2;
SELECT idstat.relname AS table_name,
indexrelname AS index_name,
idstat.idx_scan AS times_used,
pg_size_pretty(pg_table_size(idstat.relname)) AS table_size, pg_size_pretty(pg_table_size(indexrelname)) AS index_size,
n_tup_upd + n_tup_ins + n_tup_del as num_writes,
indexdef AS definition
FROM pg_stat_user_indexes AS idstat JOIN pg_indexes ON indexrelname = indexname
JOIN pg_stat_user_tables AS tabstat ON idstat.relname = tabstat.relname
WHERE idstat.idx_scan < 200
AND indexdef !~* 'unique'
ORDER BY idstat.relname, indexrelname;
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