PostgreSQL index monitor——监控哪些表需要创建索引

在数据库的使用过程中，可能某些表随着数据量的增大而因为没有索引仍旧使用的全表扫描，我们可以使用下列脚本来监控哪些大表上需要创建索引。

1、监控哪些表需要创建索引

SELECT 
	relname AS TableName
	,seq_scan-idx_scan AS TotalSeqScan
	,CASE WHEN seq_scan-idx_scan > 0 
		THEN 'Missing Index Found' 
		ELSE 'Missing Index Not Found' 
	END AS MissingIndex
	,pg_size_pretty(pg_relation_size(relname::regclass)) AS TableSize
	,idx_scan AS TotalIndexScan
FROM pg_stat_all_tables
WHERE schemaname='public'
	AND pg_relation_size(relname::regclass)>1000000  --单位字节
ORDER BY 2 DESC;

2、监控索引大小及使用情况

使用下面脚本来查看索引的大小和索引扫描的行数等信息。

SELECT
    pt.tablename AS TableName
    ,t.indexname AS IndexName
    ,pc.reltuples AS TotalRows
    ,pg_size_pretty(pg_relation_size(quote_ident(pt.tablename)::text)) AS TableSize
    ,pg_size_pretty(pg_relation_size(quote_ident(t.indexrelname)::text)) AS IndexSize
    ,t.idx_scan AS TotalNumberOfScan
    ,t.idx_tup_read AS TotalTupleRead
    ,t.idx_tup_fetch AS TotalTupleFetched
FROM pg_tables AS pt
LEFT OUTER JOIN pg_class AS pc 
	ON pt.tablename=pc.relname
LEFT OUTER JOIN
( 
	SELECT 
		pc.relname AS TableName
		,pc2.relname AS IndexName
		,psai.idx_scan
		,psai.idx_tup_read
		,psai.idx_tup_fetch
		,psai.indexrelname 
	FROM pg_index AS pi
	JOIN pg_class AS pc 
		ON pc.oid = pi.indrelid
	JOIN pg_class AS pc2 
		ON pc2.oid = pi.indexrelid
	JOIN pg_stat_all_indexes AS psai 
		ON pi.indexrelid = psai.indexrelid 
)AS T
    ON pt.tablename = T.TableName
WHERE pt.schemaname='public'
ORDER BY 1;