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分享2021年12月19日摸鱼打卡
学习目标
学习openGauss收集统计信息、打印执行计划、垃圾收集和checkpoint
课程学习
连接数据库
#第一次进入等待15秒 #数据库启动中... su - omm gsql -r
1.准备数据
Create schema tpcds; CREATE TABLE tpcds.customer_address ( ca_address_sk integer NOT NULL , ca_address_id character(16), ca_street_number character(10) , ca_street_name character varying(60) , ca_street_type character(15) , ca_suite_number character(10) , ca_city character varying(60) , ca_county character varying(30) , ca_state character(2) , ca_zip character(10) , ca_country character varying(20) , ca_gmt_offset numeric(5,2) , ca_location_type character(20) ); insert into tpcds.customer_address values (1, 'AAAAAAAABAAAAAAA', '18', 'Jackson', 'Parkway', 'Suite 280', 'Fairfield', 'Maricopa County', 'AZ', '86192' ,'United States', -7.00, 'condo'), (2, 'AAAAAAAACAAAAAAA', '362', 'Washington 6th', 'RD', 'Suite 80', 'Fairview', 'Taos County', 'NM', '85709', 'United States', -7.00, 'condo'), (3, 'AAAAAAAADAAAAAAA', '585', 'Dogwood Washington', 'Circle', 'Suite Q', 'Pleasant Valley', 'York County', 'PA', '12477', 'United States', -5.00, 'single family');
–使用序列的generate_series(1,N)函数对表插入数据
insert into tpcds.customer_address values(generate_series(10, 10000));
2.收集统计信息
–查看系统表中表的统计信息
select relname, relpages, reltuples from pg_class where relname = 'customer_address';
—使用ANALYZE VERBOSE语句更新统计信息，并输出表的相关信息
analyze VERBOSE tpcds.customer_address;
–查看系统表中表的统计信息
select relname, relpages, reltuples from pg_class where relname = 'customer_address';
3.打印执行计划
–使用默认的打印格式
SET explain_perf_mode=normal;
–显示表简单查询的执行计划
EXPLAIN SELECT * FROM tpcds.customer_address;
–以JSON格式输出的执行计划（explain_perf_mode为normal时）
EXPLAIN(FORMAT JSON) SELECT * FROM tpcds.customer_address;
–禁止开销估计的执行计划
EXPLAIN(COSTS FALSE)SELECT * FROM tpcds.customer_address;
–带有聚集函数查询的执行计划
EXPLAIN SELECT SUM(ca_address_sk) FROM tpcds.customer_address WHERE ca_address_sk<100;
–有索引条件的执行计划
create index customer_address_idx on tpcds.customer_address(ca_address_sk); EXPLAIN SELECT * FROM tpcds.customer_address WHERE ca_address_sk<100;
4.垃圾收集
–VACUUM回收表或B-Tree索引中已经删除的行所占据的存储空间
update tpcds.customer_address set ca_address_sk = ca_address_sk + 1 where ca_address_sk <100; VACUUM (VERBOSE, ANALYZE) tpcds.customer_address;
5.事务日志检查点
–检查点（CHECKPOINT）是一个事务日志中的点，所有数据文件都在该点被更新以反映日志中的信息，所有数据文件都将被刷新到磁盘CHECKPOINT;
6.清理数据
drop schema tpcds cascade;
课后作业
1.创建分区表，并用generate_series(1,N)函数对表插入数据
omm=# Create schema tpcds; CREATE SCHEMA omm=# CREATE TABLE tpcds.customer_address omm-# ( omm(# ca_address_sk integer NOT NULL , omm(# ca_address_id character(16) , omm(# ca_street_number character(10) , omm(# ca_street_name character varying(60) , omm(# ca_street_type character(15) , omm(# ca_suite_number character(10) , omm(# omm(# ca_city character varying(60) , ca_county character varying(30) , omm(# ca_state character(2) , omm(# ca_zip character(10) , omm(# ca_country character varying(20) , omm(# ca_gmt_offset numeric(5,2) , omm(# ca_location_type character(20) omm(# ) omm-# PARTITION BY RANGE (ca_address_sk) omm-# ( omm(# PARTITION P1 VALUES LESS THAN(2000), omm(# PARTITION P2 VALUES LESS THAN(6000), omm(# PARTITION P3 VALUES LESS THAN(10000) omm(# ) omm-# ENABLE ROW MOVEMENT; CREATE TABLE omm=# insert into tpcds.customer_address values(generate_series(10, 9999)); INSERT 0 9990
2.收集表统计信息
omm=# select relname, relpages, reltuples from pg_class where relname = 'customer_address'; relname | relpages | reltuples ------------------+----------+----------- customer_address | 0 | 0 (1 row) omm=# analyze VERBOSE tpcds.customer_address; INFO: analyzing "tpcds.customer_address"(gaussdb pid=1) INFO: ANALYZE INFO : "customer_address": scanned 22 of 22 pages, containing 1990 live rows and 1990 dead rows; 1990 rows in sample, 1990 estimated total rows(gaussdb pid=1) INFO: ANALYZE INFO : "customer_address": scanned 44 of 44 pages, containing 4000 live rows and 4000 dead rows; 4000 rows in sample, 4000 estimated total rows(gaussdb pid=1) INFO: ANALYZE INFO : "customer_address": scanned 44 of 44 pages, containing 4000 live rows and 4000 dead rows; 4000 rows in sample, 4000 estimated total rows(gaussdb pid=1) ANALYZE omm=# select relname, relpages, reltuples from pg_class where relname = 'customer_address'; relname | relpages | reltuples ------------------+----------+----------- customer_address | 110 | 9990 (1 row)
3.显示简单查询的执行计划；建立索引并显示有索引条件的执行计划
omm=# SET explain_perf_mode=normal; SET omm=# EXPLAIN SELECT * FROM tpcds.customer_address; QUERY PLAN ----------------------------------------------------------------------------------------- Partition Iterator (cost=0.00..209.90 rows=9990 width=788) Iterations: 3 -> Partitioned Seq Scan on customer_address (cost=0.00..209.90 rows=9990 width=788) Selected Partitions: 1..3 (4 rows) omm=# create index customer_address_idx on tpcds.customer_address(ca_address_sk); CREATE INDEX omm=# EXPLAIN SELECT * FROM tpcds.customer_address WHERE ca_address_sk<100; QUERY PLAN ------------------------------------------------------------------------------------------------ Index Scan using customer_address_idx on customer_address (cost=0.00..9.84 rows=91 width=788) Index Cond: (ca_address_sk < 100) (2 rows)
4.更新表数据，并做垃圾收集
omm=# update tpcds.customer_address set ca_address_sk = ca_address_sk + 1 where ca_address_sk <100; UPDATE 90 omm=# VACUUM (VERBOSE, ANALYZE) tpcds.customer_address; INFO: vacuuming "tpcds.customer_address"(gaussdb pid=1) INFO: scanned index "customer_address_idx" to remove 1990 row versions(gaussdb pid=1) DETAIL: CPU 0.00s/0.00u sec elapsed 0.00 sec. DETAIL: 90 dead row versions cannot be removed yet. There were 0 unused item pointers. 0 pages are entirely empty. CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: index "customer_address_idx" now contains 2080 row versions in 31 pages(gaussdb pid=1) DETAIL: 0 index row versions were removed. 0 index pages have been deleted, 0 are currently reusable. CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: "customer_address": found 1990 removable, 2080 nonremovable row versions in 22 out of 22 pages(gaussdb pid=1) INFO: vacuuming "tpcds.customer_address"(gaussdb pid=1) INFO: scanned index "customer_address_idx" to remove 4000 row versions(gaussdb pid=1) DETAIL: CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: index "customer_address_idx" now contains 4000 row versions in 31 pages(gaussdb pid=1) DETAIL: 0 index row versions were removed. 0 index pages have been deleted, 0 are currently reusable. CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: "customer_address": found 4000 removable, 4000 nonremovable row versions in 44 out of 44 pages(gaussdb pid=1) DETAIL: 0 dead row versions cannot be removed yet. There were 0 unused item pointers. 0 pages are entirely empty. CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: vacuuming "tpcds.customer_address"(gaussdb pid=1) INFO: scanned index "customer_address_idx" to remove 4000 row versions(gaussdb pid=1) DETAIL: CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: index "customer_address_idx" now contains 4000 row versions in 31 pages(gaussdb pid=1) DETAIL: 0 index row versions were removed. 0 index pages have been deleted, 0 are currently reusable. CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: "customer_address": found 4000 removable, 4000 nonremovable row versions in 44 out of 44 pages(gaussdb pid=1) DETAIL: 0 dead row versions cannot be removed yet. There were 0 unused item pointers. 0 pages are entirely empty. CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: scanned index "customer_address_idx" to remove 0.000000 invisible rows(gaussdb pid=1) DETAIL: CPU 0.00s/0.00u sec elapsed 0.00 sec. INFO: analyzing "tpcds.customer_address"(gaussdb pid=1) INFO: ANALYZE INFO : "customer_address": scanned 22 of 22 pages, containing 1990 live rows and 90 dead rows; 1990 rows in sample, 1990 estimated total rows(gaussdb pid=1) INFO: ANALYZE INFO : "customer_address": scanned 44 of 44 pages, containing 4000 live rows and 0 dead rows; 4000 rows in sample, 4000 estimated total rows(gaussdb pid=1) INFO: ANALYZE INFO : "customer_address": scanned 44 of 44 pages, containing 4000 live rows and 0 dead rows; 4000 rows in sample, 4000 estimated total rows(gaussdb pid=1) VACUUM
5.清理数据
omm=# drop schema tpcds cascade; NOTICE: drop cascades to table tpcds.customer_address DROP SCHEMA
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