我正在寻找一种方法,为我在Postgres中所有的表找到行数。我知道我可以一次做一张表:
SELECT count(*) FROM table_name;
但我想看看所有表的行数,然后按它排序,以了解所有表的大小。
我正在寻找一种方法,为我在Postgres中所有的表找到行数。我知道我可以一次做一张表:
SELECT count(*) FROM table_name;
但我想看看所有表的行数,然后按它排序,以了解所有表的大小。
当前回答
要获得估计,请参阅格雷格·史密斯的答案。
为了得到确切的数字,到目前为止,其他答案都受到一些问题的困扰,其中一些问题很严重(见下文)。这里有一个版本,希望更好:
CREATE FUNCTION rowcount_all(schema_name text default 'public')
RETURNS table(table_name text, cnt bigint) as
$$
declare
table_name text;
begin
for table_name in SELECT c.relname FROM pg_class c
JOIN pg_namespace s ON (c.relnamespace=s.oid)
WHERE c.relkind = 'r' AND s.nspname=schema_name
LOOP
RETURN QUERY EXECUTE format('select cast(%L as text),count(*) from %I.%I',
table_name, schema_name, table_name);
END LOOP;
end
$$ language plpgsql;
它接受模式名作为参数,如果没有给出参数,则接受public。
要使用特定的模式列表或来自查询的列表而不修改函数,可以从查询中调用它,如下所示:
WITH rc(schema_name,tbl) AS (
select s.n,rowcount_all(s.n) from (values ('schema1'),('schema2')) as s(n)
)
SELECT schema_name,(tbl).* FROM rc;
这将生成一个包含模式、表和行计数的3列输出。
下面是这个函数避免的其他答案中的一些问题:
Table and schema names shouldn't be injected into executable SQL without being quoted, either with quote_ident or with the more modern format() function with its %I format string. Otherwise some malicious person may name their table tablename;DROP TABLE other_table which is perfectly valid as a table name. Even without the SQL injection and funny characters problems, table name may exist in variants differing by case. If a table is named ABCD and another one abcd, the SELECT count(*) FROM... must use a quoted name otherwise it will skip ABCD and count abcd twice. The %I of format does this automatically. information_schema.tables lists custom composite types in addition to tables, even when table_type is 'BASE TABLE' (!). As a consequence, we can't iterate oninformation_schema.tables, otherwise we risk having select count(*) from name_of_composite_type and that would fail. OTOH pg_class where relkind='r' should always work fine. The type of COUNT() is bigint, not int. Tables with more than 2.15 billion rows may exist (running a count(*) on them is a bad idea, though). A permanent type need not to be created for a function to return a resultset with several columns. RETURNS TABLE(definition...) is a better alternative.
其他回答
不确定bash中的答案对您来说是否可以接受,但FWIW…
PGCOMMAND=" psql -h localhost -U fred -d mydb -At -c \"
SELECT table_name
FROM information_schema.tables
WHERE table_type='BASE TABLE'
AND table_schema='public'
\""
TABLENAMES=$(export PGPASSWORD=test; eval "$PGCOMMAND")
for TABLENAME in $TABLENAMES; do
PGCOMMAND=" psql -h localhost -U fred -d mydb -At -c \"
SELECT '$TABLENAME',
count(*)
FROM $TABLENAME
\""
eval "$PGCOMMAND"
done
要获得估计,请参阅格雷格·史密斯的答案。
为了得到确切的数字,到目前为止,其他答案都受到一些问题的困扰,其中一些问题很严重(见下文)。这里有一个版本,希望更好:
CREATE FUNCTION rowcount_all(schema_name text default 'public')
RETURNS table(table_name text, cnt bigint) as
$$
declare
table_name text;
begin
for table_name in SELECT c.relname FROM pg_class c
JOIN pg_namespace s ON (c.relnamespace=s.oid)
WHERE c.relkind = 'r' AND s.nspname=schema_name
LOOP
RETURN QUERY EXECUTE format('select cast(%L as text),count(*) from %I.%I',
table_name, schema_name, table_name);
END LOOP;
end
$$ language plpgsql;
它接受模式名作为参数,如果没有给出参数,则接受public。
要使用特定的模式列表或来自查询的列表而不修改函数,可以从查询中调用它,如下所示:
WITH rc(schema_name,tbl) AS (
select s.n,rowcount_all(s.n) from (values ('schema1'),('schema2')) as s(n)
)
SELECT schema_name,(tbl).* FROM rc;
这将生成一个包含模式、表和行计数的3列输出。
下面是这个函数避免的其他答案中的一些问题:
Table and schema names shouldn't be injected into executable SQL without being quoted, either with quote_ident or with the more modern format() function with its %I format string. Otherwise some malicious person may name their table tablename;DROP TABLE other_table which is perfectly valid as a table name. Even without the SQL injection and funny characters problems, table name may exist in variants differing by case. If a table is named ABCD and another one abcd, the SELECT count(*) FROM... must use a quoted name otherwise it will skip ABCD and count abcd twice. The %I of format does this automatically. information_schema.tables lists custom composite types in addition to tables, even when table_type is 'BASE TABLE' (!). As a consequence, we can't iterate oninformation_schema.tables, otherwise we risk having select count(*) from name_of_composite_type and that would fail. OTOH pg_class where relkind='r' should always work fine. The type of COUNT() is bigint, not int. Tables with more than 2.15 billion rows may exist (running a count(*) on them is a bad idea, though). A permanent type need not to be created for a function to return a resultset with several columns. RETURNS TABLE(definition...) is a better alternative.
如果您不介意可能过时的数据,您可以访问查询优化器使用的相同统计信息。
喜欢的东西:
SELECT relname, n_tup_ins - n_tup_del as rowcount FROM pg_stat_all_tables;
下面是一个解决方案,它不需要函数来获得每个表的精确计数:
select table_schema,
table_name,
(xpath('/row/cnt/text()', xml_count))[1]::text::int as row_count
from (
select table_name, table_schema,
query_to_xml(format('select count(*) as cnt from %I.%I', table_schema, table_name), false, true, '') as xml_count
from information_schema.tables
where table_schema = 'public' --<< change here for the schema you want
) t
query_to_xml将运行传递的SQL查询并返回带有结果的XML(该表的行数)。外层xpath()将从该xml中提取计数信息并将其转换为数字
实际上并不需要派生表,但可以使xpath()更容易理解——否则整个query_to_xml()将需要传递给xpath()函数。
我喜欢Daniel Vérité的回答。 但是当你不能使用CREATE语句时,你可以使用bash解决方案,如果你是windows用户,可以使用powershell解决方案:
# You don't need this if you have pgpass.conf
$env:PGPASSWORD = "userpass"
# Get table list
$tables = & 'C:\Program Files\PostgreSQL\9.4\bin\psql.exe' -U user -w -d dbname -At -c "select table_name from information_schema.tables where table_type='BASE TABLE' AND table_schema='schema1'"
foreach ($table in $tables) {
& 'C:\path_to_postresql\bin\psql.exe' -U root -w -d dbname -At -c "select '$table', count(*) from $table"
}