一、圖形化在線分析工具
二、執(zhí)行分析語(yǔ)句
EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS, FORMAT JSON)
select * from ...
生成分析JSON之后，填入圖形化分析頁(yè)面，進(jìn)行分析。
三、分析樣例
1、走索引 - Index Scan Node
表示先走二級(jí)索引，再走一級(jí)索引找到數(shù)據(jù)
finds relevant records based on an Index. Index Scans perform 2 read operations: one to read the index and another to read the actual value from the table.
2、順序掃描 - Seq Scan Node
finds relevant records by sequentially scanning the input record set. When reading from a table, Seq Scans (unlike Index Scans) perform a single read operation (only the table is read).
3、緩存 - shared
- Hit - 命中
- Read - 讀磁盤(pán)
- Dirtied - 臟頁(yè)(臟頁(yè)包含在Hit中)
4、循環(huán)匹配 - Nested Loop
join數(shù)據(jù)，將兩個(gè)結(jié)果集進(jìn)行拼接
merges two record sets by looping through every record in the first set and trying to find a match in the second set. All matching records are returned.
遍歷模式
索引模式
5、聚合 - Aggregate
group by 操作
groups records together based on a GROUP BY or aggregate function (like sum()).
6、排序 - Sort
order by 操作
sorts a record set based on the specified sort key.
7、數(shù)量限制 - limit
returns a specified number of rows from a record set.
8、with as 臨時(shí)表 - Common table expressions - CTE
performs a sequential scan of Common Table Expression (CTE) query results. Note that results of a CTE are materialized (calculated and temporarily stored).
對(duì)公共表表達(dá)式（CTE）查詢(xún)結(jié)果執(zhí)行順序掃描。注意，CTE的結(jié)果是具體化的（計(jì)算并臨時(shí)存儲(chǔ)）。
9、其他操作
- WindowAgg
- Subquery Scan
10、其他join模式圖解
-
Hash Join
-
Merge Join
