Postgres invalid command \N数据恢复处理
同事做一个单表恢复工作，数据在1000多W，说是报了错误导不进去，环境与流程见下：
OS:CnetOS 5
DB:Postgres 9.2.4
恢复步骤：
总结：
扩展开来想，这种备份如果是整个库备份再恢复，应是OK的，后来验证确实如此，故对于整库恢复是不用考虑这个问题的，单表恢复则需要注意一下。
OS:CnetOS 5
DB:Postgres 9.2.4
恢复步骤：
1.导出语句 pg_dump -h xxxxx -p 5432 -U postgres -b -Fp db_test -t t_kenyon -f /var/t_kenyon.bak 2.导入语句 psql -h xxxx -d new_db -U postgres < /var/t_kenyon.bak 3.报错信息，屏幕上一堆的诸如 invalid command \N invalid command \N invalid command \N invalid command \N invalid command \N invalid command \N ........分析处理：
因为是逻辑导出没有压缩定制的文件，故可以查看备份内容
[postgres@localhost ~]$ more t_kenyon.bak
--
-- PostgreSQL database dump
--
SET statement_timeout = 0;
SET client_encoding = 'UTF8';
SET standard_conforming_strings = on;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET search_path = public, pg_catalog;
SET default_tablespace = '';
SET default_with_oids = false;
--
-- Name: t_kenyon; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
--
CREATE TABLE t_kenyon (
col1 integer DEFAULT nextval('t_kenyon_col1_seq'::regclass) NOT NULL,
col2 ..
col3 ..
);
ALTER TABLE public.t_kenyon OWNER TO postgres;
--
-- Name: COLUMN t_kenyon.col; Type: COMMENT; Schema: public; Owner: postgres
--
--
-- Data for Name: t_kenyon; Type: TABLE DATA; Schema: public; Owner: postgres
--
COPY t_kenyon (col1,col2,col3....) FROM stdin;
3315866 \N 1 5.00 \N \N \N 2011-01-12 08:37:07+08 1 4130000 爱我中话 \N 708 Kenyon HZ 雅安加油 HZ01 HELLO \N 9 \N
3315934 \N 1 5.00 \N \N \N 2011-01-12 09:13:17+08 1 4130000 我哎中华 \N 708 kenyon HZ 雅安加油
..........此处略去1W字
看起来报错的信息都是\N即空格的地方出错了，检查了一下postgres的日志，有几条信息发现很有意思
2013-04-23 00:16:23.149 PDT,"postgres","postgres",24738,"[local]",51763545.60a2,4,"CREATE TABLE",2013-04-23 00:16:21 PDT,2/331,1856,ERROR,42P01,"relation ""t_kenyon_col1_seq"" does not exist",,,,,,"CREATE TABLE t_kenyon (col1,col2...)..这看起来是导数据之前的建表失败了，因为sequence不存在，后面的copy操作直接就报了N多的错误，尝试先建一下索引，再重新导入
postgres=#CREATE SEQUENCE t_kenyon_col1_seq INCREMENT 1 MINVALUE 1 MAXVALUE 9223372036854775807 START 17354062 CACHE 1; CREATE SEQUENCE postgres=# \q [postgres@localhost ~]$ psql -d postgres -U postgres < /var/t_kenyon.bak SET SET SET SET SET SET SET SET CREATE TABLE ALTER TABLE COMMENT ALTER TABLE CREATE INDEX CREATE INDEX [postgres@localhost ~]$OK,导入成功。但是有一个问题，为什么pg_dump导出的时候没有把sequence带出来呢？验证一下
[postgres@localhost ~]$ psql
psql (9.2.4)
Type "help" for help.
postgres=# \d
No relations found.
postgres=# create table d_kenyon(id serial,vname varchar(30));
NOTICE: CREATE TABLE will create implicit sequence "d_kenyon_id_seq" for serial column "d_kenyon.id"
CREATE TABLE
postgres=# insert into d_kenyon(vname) select generate_series(1,10)||'Hi,Kenyon!';
INSERT 0 10
postgres=# select * from d_kenyon;
id | vname
----+--------------
1 | 1Hi,Kenyon!
2 | 2Hi,Kenyon!
3 | 3Hi,Kenyon!
4 | 4Hi,Kenyon!
5 | 5Hi,Kenyon!
6 | 6Hi,Kenyon!
7 | 7Hi,Kenyon!
8 | 8Hi,Kenyon!
9 | 9Hi,Kenyon!
10 | 10Hi,Kenyon!
(10 rows)
postgres=# \d
List of relations
Schema | Name | Type | Owner
--------+-----------------+----------+----------
public | d_kenyon | table | postgres
public | d_kenyon_id_seq | sequence | postgres
[postgres@localhost ~]$ pg_dump -U postgres -b -Fp postgres -t d_kenyon -f d_kenyon.bak
[postgres@localhost ~]$ more d_kenyon.bak
--
-- PostgreSQL database dump
--
SET statement_timeout = 0;
SET client_encoding = 'UTF8';
SET standard_conforming_strings = on;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET search_path = public, pg_catalog;
SET default_tablespace = '';
SET default_with_oids = false;
--
-- Name: d_kenyon; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
--
CREATE TABLE d_kenyon (
id integer NOT NULL,
vname character varying(30)
);
ALTER TABLE public.d_kenyon OWNER TO postgres;
--
-- Name: d_kenyon_id_seq; Type: SEQUENCE; Schema: public; Owner: postgres
--
CREATE SEQUENCE d_kenyon_id_seq
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE
CACHE 1;
ALTER TABLE public.d_kenyon_id_seq OWNER TO postgres;
--
-- Name: d_kenyon_id_seq; Type: SEQUENCE OWNED BY; Schema: public; Owner: postgres
--
ALTER SEQUENCE d_kenyon_id_seq OWNED BY d_kenyon.id;
--
-- Name: id; Type: DEFAULT; Schema: public; Owner: postgres
--
ALTER TABLE ONLY d_kenyon ALTER COLUMN id SET DEFAULT nextval('d_kenyon_id_seq'::regclass);
--
-- Data for Name: d_kenyon; Type: TABLE DATA; Schema: public; Owner: postgres
--
COPY d_kenyon (id, vname) FROM stdin;
1 1Hi,Kenyon!
2 2Hi,Kenyon!
3 3Hi,Kenyon!
4 4Hi,Kenyon!
5 5Hi,Kenyon!
6 6Hi,Kenyon!
7 7Hi,Kenyon!
8 8Hi,Kenyon!
[postgres@localhost ~]$ psql
psql (9.2.4)
Type "help" for help.
postgres=# \d
List of relations
Schema | Name | Type | Owner
--------+-----------------+----------+----------
public | d_kenyon | table | postgres
public | d_kenyon_id_seq | sequence | postgres
(2 rows)
postgres=# drop table d_kenyon;
DROP TABLE
postgres=# \q
[postgres@localhost ~]$ psql < d_kenyon.bak
SET
SET
SET
SET
SET
SET
SET
SET
CREATE TABLE
ALTER TABLE
CREATE SEQUENCE
ALTER TABLE
ALTER SEQUENCE
ALTER TABLE
setval
--------
10
(1 row)
[postgres@localhost ~]$
发现用serial产生的sequence是可以导出并导入的，回过头再去看异常的表，发现该表字段不是serial，模拟一下非serial字段的pg_dump导出情况
postgres=# create table d_test as select * from d_kenyon;
SELECT 10
postgres=# alter table d_test alter column id set default nextval('d_kenyon_id_seq'::regclass);
ALTER TABLE
postgres=# \d d_test
Table "public.d_test"
Column | Type | Modifiers
--------+-----------------------+----------------------------------------------
id | integer | default nextval('d_kenyon_id_seq'::regclass)
vname | character varying(30) |
postgres=# \q
[postgres@localhost ~]$ pg_dump -U postgres -b -Fp postgres -t d_test -f d_kenyon.bak
[postgres@localhost ~]$ more d_kenyon.bak
--
-- PostgreSQL database dump
--
SET statement_timeout = 0;
SET client_encoding = 'UTF8';
SET standard_conforming_strings = on;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET search_path = public, pg_catalog;
SET default_tablespace = '';
SET default_with_oids = false;
--
-- Name: d_test; Type: TABLE; Schema: public; Owner: postgres; Tablespace:
--
CREATE TABLE d_test (
id integer DEFAULT nextval('d_kenyon_id_seq'::regclass),
vname character varying(30)
);
ALTER TABLE public.d_test OWNER TO postgres;
--
-- Data for Name: d_test; Type: TABLE DATA; Schema: public; Owner: postgres
--
COPY d_test (id, vname) FROM stdin;
1 1Hi,Kenyon!
2 2Hi,Kenyon!
3 3Hi,Kenyon!
4 4Hi,Kenyon!
5 5Hi,Kenyon!
6 6Hi,Kenyon!
7 7Hi,Kenyon!
8 8Hi,Kenyon!
9 9Hi,Kenyon!
10 10Hi,Kenyon!
\.
--
-- PostgreSQL database dump complete
--
确实是没有sequence导出来的，查了一下，pg_depend里序列与表并没有关联上，也就是说这样的表与sequence是独立的，可以用以下SQL验证一下表与sequence的关联关系
WITH fq_objects AS (SELECT c.oid,c.relname AS fqname ,c.relkind, c.relname AS relation FROM
pg_class c JOIN pg_namespace n ON n.oid = c.relnamespace ),
sequences AS (SELECT oid,fqname FROM fq_objects WHERE relkind = 'S'),
tables AS (SELECT oid, fqname FROM fq_objects WHERE relkind = 'r' )
SELECT s.fqname AS sequence,'->' as depends,t.fqname AS table
FROM pg_depend d JOIN sequences s ON s.oid = d.objid
JOIN tables t ON t.oid = d.refobjid
WHERE d.deptype = 'a' and t.fqname = 'd_kenyon';
总结：
扩展开来想，这种备份如果是整个库备份再恢复，应是OK的，后来验证确实如此，故对于整库恢复是不用考虑这个问题的，单表恢复则需要注意一下。