GreenPlum删除主键约束
最近使用GreenPlum（简称GP）时遇到了一个小问题，删除主键删不掉，一直报主键不存在，例子如下：
zxy=> \d tmp_cst_pcp_avy_sttn_hw
Table "a0.tmp_cst_pcp_avy_sttn_hw"
Column | Type | Modifiers
-----------------------+-----------------------+-----------
dccp_avy_id | character varying(40) | not null
avy_aw_cnd_id | character varying(20) | not null
cst_id | character varying(18) | not null
multi_tenancy_id | character varying(5) | not null
stat_dt | date | not null
cstpcpavyfit_cnd_dnum | numeric(5,0) |
cstpcpavyfitcnd_acamt | numeric(15,2) |
avy_aw_rslt_stcd | character varying(2) |
ccycd | character varying(3) |
cardno | character varying(19) |
txn_dt | date |
prz_tpcd | character varying(2) |
aspd_id | character varying(8) |
Indexes:
"tmp_cst_pcp_avy_sttn_hw_pkey" PRIMARY KEY, btree (dccp_avy_id, avy_aw_cnd_id, cst_id, stat_dt, multi_tenancy_id)
Distributed by: (dccp_avy_id, avy_aw_cnd_id, cst_id, stat_dt, multi_tenancy_id)
zxy=> alter table tmp_cst_pcp_avy_sttn_hw drop constraint tmp_cst_pcp_avy_sttn_hw_pkey cascade;
ERROR: constraint "tmp_cst_pcp_avy_sttn_hw_pkey" does not exist
不加模式名和加模式名都尝试了，都删不掉
zxy=> alter table a0.tmp_cst_pcp_avy_sttn_hw drop constraint tmp_cst_pcp_avy_sttn_hw_pkey cascade;
ERROR: constraint "tmp_cst_pcp_avy_sttn_hw_pkey" does not exist想了很多招，最后翻数据字典，找到解决的办法，发现\d 查看表结构的和实际存在数据字典上的不太一样
例如：
zxy=> \d tmp_cst_pcp_avy_sttn_hw
Table "a0.tmp_cst_pcp_avy_sttn_hw"
Column | Type | Modifiers
-----------------------+-----------------------+-----------
dccp_avy_id | character varying(40) | not null
avy_aw_cnd_id | character varying(20) | not null
cst_id | character varying(18) | not null
multi_tenancy_id | character varying(5) | not null
stat_dt | date | not null
cstpcpavyfit_cnd_dnum | numeric(5,0) |
cstpcpavyfitcnd_acamt | numeric(15,2) |
avy_aw_rslt_stcd | character varying(2) |
ccycd | character varying(3) |
cardno | character varying(19) |
txn_dt | date |
prz_tpcd | character varying(2) |
aspd_id | character varying(8) |
Indexes:
"tmp_cst_pcp_avy_sttn_hw_pkey" PRIMARY KEY, btree (dccp_avy_id, avy_aw_cnd_id, cst_id, stat_dt, multi_tenancy_id)
Distributed by: (dccp_avy_id, avy_aw_cnd_id, cst_id, stat_dt, multi_tenancy_id)
这个时候以为该表的主键是tmp_cst_pcp_avy_sttn_hw_pkey
实际上
zxy=> select oid from pg_class where relname='tmp_cst_pcp_avy_sttn_hw';
oid
-------
54934
(1 row)
zxy=> \d pg_constraint
Table "pg_catalog.pg_constraint"
Column | Type | Modifiers
---------------+------------+-----------
conname | name | not null
connamespace | oid | not null
contype | "char" | not null
condeferrable | boolean | not null
condeferred | boolean | not null
conrelid | oid | not null
contypid | oid | not null
confrelid | oid | not null
confupdtype | "char" | not null
confdeltype | "char" | not null
confmatchtype | "char" | not null
conkey | smallint[] |
confkey | smallint[] |
conbin | text |
consrc | text |
Indexes:
"pg_constraint_oid_index" UNIQUE, btree (oid)
"pg_constraint_conname_nsp_index" btree (conname, connamespace)
"pg_constraint_conrelid_index" btree (conrelid)
"pg_constraint_contypid_index" btree (contypid)
zxy=> select conname from pg_constraint where conrelid=54934;
conname
---------------------
pk_cst_pcp_avy_sttn
(1 row)
实际上是pk_cst_pcp_avy_sttn
发现区别了吧，这个时候再去删除主键
zxy=> alter table tmp_cst_pcp_avy_sttn_hw drop constraint pk_cst_pcp_avy_sttn cascade;
ALTER TABLE
zxy=> \d tmp_cst_pcp_avy_sttn_hw
Table "a0.tmp_cst_pcp_avy_sttn_hw"
Column | Type | Modifiers
-----------------------+-----------------------+-----------
dccp_avy_id | character varying(40) | not null
avy_aw_cnd_id | character varying(20) | not null
cst_id | character varying(18) | not null
multi_tenancy_id | character varying(5) | not null
stat_dt | date | not null
cstpcpavyfit_cnd_dnum | numeric(5,0) |
cstpcpavyfitcnd_acamt | numeric(15,2) |
avy_aw_rslt_stcd | character varying(2) |
ccycd | character varying(3) |
cardno | character varying(19) |
txn_dt | date |
prz_tpcd | character varying(2) |
aspd_id | character varying(8) |
Distributed by: (dccp_avy_id, avy_aw_cnd_id, cst_id, stat_dt, multi_tenancy_id)
zxy=> 完全删除了
总结：GP删除主键的语句：ALTER TABLE 表名 DROP CONSTRAINT 约束名 [RESTRICT | CASCADE]
如果报约束名不存在时，去数据字典（pg_class和pg_constraint）中查找，去查实际的约束名