# 创建一个表mydb=# create table testtable1(id int, tname varchar(20));mydb=# insert into testtable1 select n,'myname_'||n from generate_series(1,5000000) n;mydb=# explain analyze select * from testtable1 where tname='myname_10';QUERY PLAN --- Gather (cost=1000.00..58878.99 ...
在REPEATABLE READ 隔离级别下,一个事务在执行过程中只有第一次执行SELECT操作才会生成一个ReadView,之后的SELECT操作都复用这个ReadView,这样也就避免了不可重复读和幻读的问题。 2.4.1 方案二:读、写操作都采用加锁的方式 如果我们的一些业务场景不允许读取记录的旧版本,而是每次都必须去读取记录的最新版本。这样在...
# 从系统表中获取表的统计信息 mydb=# select oid,relname,relpages,reltuples from pg_class where relname='testprimarykey'; -[ RECORD 1 ]--- oid | 16768 relname | testprimarykey relpages | 0 reltuples | -1 mydb=# select * from pg_stats where tablename='testprimarykey'; 1. 2. 3...
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SELECT ON test_table TO test_user1; GRANT postgres=# grant select (id),update (name) ON test_table TO test_user1; GRANT postgres=# \dp+ test_table *** QUERY *** SELECT n.nspname as "Schema", c.relname as "Name", CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view...
I am trying to runt he following select statement on a table in order search for duplicate rows in the table select column1,column2,column3,count() from table group by column1,column2,column3 having count() > 1; This however gives me the following error: ...
摘要:If the data in your tables do not have integrity, meaning there are missing rows, incorrect values, or duplicate rows, your table is not worth much. D 阅读全文 posted @ 2020-08-28 19:30 Zhentiw 阅读(149) 评论(0) 推荐(0) [...
(We * cannot fall out earlier, however, since we need to scan the bucket to * check for duplicate keys.) */ if (bucket != newbucket) { /* OK to remove record from old hash bucket's chain. */ //从旧的里面删除,挂到新的上面 *oldPrevPtr = currBucket->link; /* link into new...
However, I am missing the extra Olive Oil record. To display that record, I need to swapUNIONforUNION ALL. SELECT*FROMpastaUNIONALLSELECT*FROMpizza; Copy |Ingredient|NeedtoBuy|---+---|Dough|No||PizzaSauce|Yes||PastaSauce|No||OliveOil|Yes||DryPasta|Yes||OliveOil|Yes||Cheese|No| Copy...
INSERT INTO "Table" (columnsList) (SELECT columnsList FROM "Table_Temp721dc9be") LIMIT 1 ON CONFLICT ("UniqueField") DO NOTHING RETURNING columnsList which seems to be correct except the LIMIT 1 part. It only inserts 1 non-duplicate record from the list of records I am passing in to ...