#查看库中所有的索引
select * from pg_stat_user_indexes
#查看某张表的索引
select * from pg_stat_user_indexes where relname = '表名' ;
#创建索引
create index index_name ON table_name (column1_name, column2_name);
#删除索引
drop index index_name;
#创建空间索引
create index idx_geom_ ON nyc_census_blocks using GIST (geom);