我有一个名为带有触发器的证据表,它调用一个存储过程,它基本上按月进行表分区.但是,当我开始在加载下插入大量行时,我得到一个模糊的错误:
Npgsql.NpgsqlException: query string argument of EXECUTE is null Severity: ERROR Code: 22004 at Npgsql.NpgsqlState.d__a.MoveNext() in c:\C#Apps\github.npgsql.Npgsql.stock\src\Npgsql\NpgsqlState.cs:line890 at Npgsql.ForwardsOnlyDataReader.GetNextResponseObject() in c:\C#Apps\github.npgsql.Npgsql.stock\src\Npgsql\NpgsqlDataReader.cs:line 1175 at Npgsql.ForwardsOnlyDataReader.GetNextRowDescription() in c:\C#Apps\github.npgsql.Npgsql.stock\src\Npgsql\NpgsqlDataReader.cs:line 1191 at Npgsql.ForwardsOnlyDataReader.NextResult() in c:\C#Apps\github.npgsql.Npgsql.stock\src\Npgsql\NpgsqlDataReader.cs:line 1377 at Npgsql.NpgsqlCommand.ExecuteNonQuery() in c:\C#Apps\github.npgsql.Npgsql.stock\src\Npgsql\NpgsqlCommand.cs:line523
我的系统具有自动重试功能,最终每个记录都插入到数据库中,但是在负载很高的许多异常之后.
数据库是CentOS 6服务器上的PostgreSQL 9.3,客户端是使用Npgsql驱动程序的C#.NET.
表:
CREATE TABLE evidence ( id uuid NOT NULL, notification_id uuid NOT NULL, feedback character varying(200), result character varying(20), trigger_action_type character varying(200), trigger_action_id uuid, data_type integer NOT NULL, data bytea, name character varying(30), CONSTRAINT pk_evidence PRIMARY KEY (id) );
触发:
CREATE TRIGGER evidence_move_to_partition_tables BEFORE INSERT ON evidence FOR EACH ROW EXECUTE PROCEDURE partition_evidence_by_month();
触发功能:
CREATE OR REPLACE FUNCTION partition_evidence_by_month() RETURNS trigger AS $BODY$ DECLARE _notification_id uuid; _raised_local_time timestamp without time zone; _table_name character varying(35); _start_date timestamp without time zone; _end_date timestamp without time zone; _table_space character varying(50) := 'ls_tablespace2'; _query text; BEGIN _notification_id := NEW.notification_id; SELECT raised_local_time FROM notifications WHERE id=_notification_id INTO _raised_local_time; _start_date := date_trunc('month', _raised_local_time); _end_date := _start_date + '1 month'::interval; _table_name := 'evidence-' || to_char(_start_date, 'YYYY-MM'); -- check to see if table already exists PERFORM 1 FROM pg_catalog.pg_class c JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relkind = 'r' AND c.relname = _table_name AND n.nspname = 'public'; -- if the table doesn't exist, then create it now IF NOT FOUND THEN -- create partition table _query := 'CREATE TABLE public.' || quote_ident(_table_name) || ' ( ) INHERITS (public.evidence)'; EXECUTE _query; -- alter owner --EXECUTE 'ALTER TABLE public.' || quote_ident(_table_name) || ' OWNER TO postgres'; -- add index --EXECUTE 'ALTER TABLE public.' || quote_ident(_table_name) || ' ADD PRIMARY KEY (id)'; END IF; -- move the data to the partition table EXECUTE 'INSERT INTO public.' || quote_ident(_table_name) || ' VALUES ($1.*)' USING NEW; RETURN NULL; END; $BODY$ LANGUAGE plpgsql VOLATILE COST 100;
电话代码:
using (var cmd = db.CreateCommand()) { cmd.CommandText = @"INSERT INTO evidence (id, notification_id, feedback, result, trigger_action_type, trigger_action_id, data_type, data, name) VALUES (@id,@nid,@feedback,@result,@tat,@taid,@dt,@data,@name)"; cmd.Parameters.AddWithValue("@id", evItem.ID); cmd.Parameters.AddWithValue("@nid", evItem.NotificationID); cmd.Parameters.AddWithValue("@feedback", evItem.Feedback); cmd.Parameters.AddWithValue("@result", evItem.Result); cmd.Parameters.AddWithValue("@tat", evItem.TriggerActionType); cmd.Parameters.AddWithValue("@taid", evItem.TriggerActionID); cmd.Parameters.AddWithValue("@dt", (int)evItem.DataType); cmd.Parameters.AddWithValue("@data", evItem.Data); cmd.Parameters.AddWithValue("@name", evItem.Name); cmd.ExecuteNonQuery(); }
为什么只有在系统负载不足时才会出现这种奇怪的错误?我该怎么做才能防止它发生?
谢谢!
错误消息是
EXECUTE的查询字符串参数为null
你有两个EXECUTE
命令:
_query := 'CREATE TABLE public.'
|| quote_ident(_table_name) || ' ( ) INHERITS (public.evidence)';
EXECUTE _query;
...
EXECUTE 'INSERT INTO public.'
|| quote_ident(_table_name) || ' VALUES ($1.*)' USING NEW;
唯一可能的部分NULL
是table_name
.成为
唯一的机会就在这里:table_name
NULL
SELECT raised_local_time FROM notifications WHERE id=_notification_id
INTO _raised_local_time;
因此,原因必须是以下两个原因之一:
NEW.notification_id
是NULL
.
notifications
给定的没有行NEW.notification_id
.
CREATE OR REPLACE FUNCTION partition_evidence_by_month()
RETURNS trigger AS
$func$
DECLARE
_table_name text;
BEGIN
SELECT 'evidence-' || to_char(raised_local_time, 'YYYY-MM')
FROM public.notifications -- schema-qualify to be sure
WHERE id = NEW.notification_id
INTO _table_name;
IF _table_name IS NULL THEN
RAISE EXCEPTION '_table_name is NULL. Should not occur!';
END IF;
IF NOT EXISTS ( -- create table if it does not exist
SELECT 1
FROM pg_catalog.pg_class c
JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relkind = 'r'
AND c.relname = _table_name
AND n.nspname = 'public') THEN
EXECUTE 'CREATE TABLE public.'
|| quote_ident(_table_name) || ' ( ) INHERITS (public.evidence)';
END IF;
EXECUTE 'INSERT INTO public.'
|| quote_ident(_table_name) || ' VALUES $1' -- Use NEW row directly
USING NEW; -- write data to the partition table
RETURN NULL;
END
$func$ LANGUAGE plpgsql;
删除未使用的变量并简化代码.(这显然是一个简化的例子.)
除此之外,你根本不需要date_trunc()
.只需将原始时间戳输入即可to_char()
.
使用没有意义varchar(n)
.只需使用text
或varchar
.
避免太多不必要的任务 - 在PL/pgSQL中相对昂贵.
添加一个RAISE
来检查我的假设.
如果您收到错误消息,则可以在下一步中区分两种可能的原因.应该是微不足道的......