I have some table in mariadb.
I need to create foreign table partition for that table
CREATE TABLE IF NOT EXISTS users (
id serial NOT NULL,
name varchar(30)
) partition by range(id);
CREATE foreign TABLE IF NOT EXISTS users_p
partition of users for values from(0) to (10000)
SERVER test22
options (table_name 'users');
If i try to get some data all is OK
but then i try insert something
insert into users (id,name) values (111,'somename');
I got an error (text depends on fdw)
COPY and foreign partition routing not supported in mysql_fdw
i tried two variants of fdw.
EnterpriseDB/mysql_fdw and pgspider/jdbc_fdw
Is there a fdw that supports insert if foreign table is partition? Or any variants how can i realize that
pgspider/mysql_fdw - solves my problem
Related
I have a table in database like this
CREATE TABLE assignments
(
id uuid,
owner_id uuid NOT NULL,
);
Now I want to check in records , If IDs I am getting from request already exist or Not. If exist I will update owner_id and If In request I Not getting a ID which already exist in table I have to delete that record.
(In short it's update mechanism In which I am getting multiple Id's to update in table and If there is already a record in database and In request aswell I will update in database , and If there is record in table but not in request I will delete that from database)
This can be done with a single Insert statement with the ON Conflict clause. Your first task will be creating a PK (or UNIQUE) constraint on the table. Presumably that would be id.
alter table assignments
add constraint primary key (id);
Then insert your data, the 'on constraint' clause will update the owner_id for any existing id.
insert assignments(id, owner_id)
values ( <id>,<owner>)
on conflict (id)
do update
set owner_id = excluded.owner_id;
I created a table in PostgreSQL with a foreign key constraint.
I dropped the table to which the foreign key belongs. Now how to alter the table or how to defer the foreign key present in the table?
To clarify:
I have a table named test. It has a column called subjectName, which is a foreign key of subject Table. Now I dropped subject table. How to remove the FK constaint on table test
Assuming the following tables:
create table subject
(
name varchar(10) primary key
);
create table test
(
some_column integer,
subject_name varchar(10) not null references subject
);
there are two scenarios what could have happened when you dropped the table subject:
1. you didn't actually drop it:
drop table subject;
ERROR: cannot drop table subject because other objects depend on it
Detail: constraint test_subject_name_fkey on table test depends on table subject
Hint: Use DROP ... CASCADE to drop the dependent objects too.
2. you did drop it, then the foreign key is gone as well.
drop table subject cascade;
NOTICE: drop cascades to constraint test_subject_name_fkey on table test
which tells you that the foreign key constraint was automatically dropped.
Perhaps your question in not exactly what you mean. Are you wanting to remove the which was a foreign key from the table. As amply indicated if you dropped the parent table then the FK is also dropped. However the column itself is not dropped from the child table. To remove that you need to alter the table.
alter table test drop column subject_name;
See demo here
I'm trying to partitioning a table with existing rows in Postgresql 10.8.
The structure is like this :
I'm trying to create partitions of table Item, it has around 5mill of rows.
I create the partitions with those commands:
CREATE TABLE item_1 (CHECK (id >0 AND id <1000001)) INHERITS (item);
CREATE TABLE item_2 (CHECK (id >1000000 AND id <2000001)) INHERITS (item);
...
Then the rules:
CREATE RULE item_1_rule AS ON INSERT TO item WHERE (id >0 AND id <1000001) DO INSTEAD INSERT INTO item_1 VALUES (NEW.*);
CREATE RULE item_2_rule AS ON INSERT TO item WHERE (id >1000000 AND id <2000001) DO INSTEAD INSERT INTO item_2 VALUES (NEW.*);
...
Then the migration to the partitioned tables:
INSERT INTO item_1 SELECT * FROM item WHERE (id >0 AND id <1000001);
INSERT INTO item_2 SELECT * FROM item WHERE (id >1000000 AND id <2000001);
...
And finally I try to Delete all the rows from the Item table:
DELETE FROM ONLY item;
But I get this error:
ERROR: update or delete on table "item" violates foreign key constraint >"item_audit_item_id_fkey" on table "item_audit"
SQL state: 23503
Detail: Key (id)=(1) is still referenced from table "item_audit".
So is it possible to drop the data from the main table Item to have only the rows on the partitions tables?
There are other alternatives to make a partition in a different way?
If you use inheritance partitioning, you won't be able to have foreign keys pointing to the partitioned table. You have to drop the constraint before you can delete the rows.
I recommend to use declarative partitioning. If you upgrade to v11 or later, you can have a foreign key pointing to a partitioned table, but since the primary key on a partitioned table has to contain the partitioning key, you'd have to add that column to the foreign key as well.
Since partitioning is mostly useful for mass data deletion, it might make sense to partition item_audit the same way.
I'm trying to find an example to create a partition table.
I have some tables with many tuples and I can classify them according to a value of one column, but, I just find examples using range and date (my column is a varchar and, in other table, is a int/foreign key).
I'm trying to speed my SELECT with this technique.
Here one of my CREATE tables (column Source will be used to partition this table):
CREATE TABLE tb_hit_source (
Hit_SourceId bigserial NOT NULL,
Source varchar(50) NOT NULL,
UniqueId varchar(50) NOT NULL,
tb_hit_HitId int8 NOT NULL,
CONSTRAINT tb_hit_source_ak_1 UNIQUE (Source, tb_hit_HitId, UniqueId) NOT DEFERRABLE INITIALLY IMMEDIATE,
CONSTRAINT tb_hit_source_pk PRIMARY KEY (Hit_SourceId)
);
CREATE INDEX tb_hit_source_idx_1 on tb_hit_source (Source ASC);
CREATE INDEX tb_hit_source_idx_2 on tb_hit_source (tb_hit_HitId ASC);
ALTER TABLE tb_hit_source ALTER COLUMN Hit_SourceId SET DEFAULT nextval('"HitSourceId_seq_tb_hit_source"');;
to create the table do.
CREATE TABLE tb_hit_source (
Hit_SourceId bigserial NOT NULL,
Source varchar(50) NOT NULL,
UniqueId varchar(50) NOT NULL,
tb_hit_HitId int8 NOT NULL,
CONSTRAINT tb_hit_source_ak_1
UNIQUE (Source, tb_hit_HitId, UniqueId) NOT DEFERRABLE,
CONSTRAINT tb_hit_source_pk PRIMARY KEY (Hit_SourceId)
PARTITION BY RANGE (Source);
then to create the partitions use the same value at each end of the range to force a single value partition.
CREATE TABLE tb_hit_source_a PARTITION OF tb_hit_source
FOR VALUES FROM ('a') TO ('a');
etc.
podtgresql 11 offers PARTITION BY LIST (source) allowing the partitions to be declared more simply.
CREATE TABLE tb_hit_source_a PARTITION OF tb_hit_source
FOR VALUES IN ('a');
to create the partitions do
create table part_a (check source='part_a' )inherits (tb_hit_source);
create table part_a (check source='part_b' )inherits (tb_hit_source);
etc.
but if there are going to be many partitions it will probably be more convenient to put them in a separate schema.
create schema hit_source_parts;
create table hit_source_parts.a (check(source='a'))inherits (tb_hit_source);
create table hit_source_parts.b (check(source='b'))inherits (tb_hit_source);
etc.
Any partitions you make will also need the aproptiate indexes.
unique constraints won't work across partitions this is one reaon why most uses of partitioning partition on one of the unique colums, by fragmenting this way uniqueness in each partition also enforces global uniqueness.
I have a postgres table (lets call this table Events) with a composite foreign key to another table (lets call this table Logs). The Events table looks like this:
CREATE TABLE Events (
ColPrimary UUID,
ColA VARCHAR(50),
ColB VARCHAR(50),
ColC VARCHAR(50),
PRIMARY KEY (ColPrimary),
FOREIGN KEY (ColA, ColB, ColC) REFERENCES Logs(ColA, ColB, ColC)
);
In this case, I know that I can efficiently search for Events by the primary key, and join to Logs.
What I am interested in is if this foreign key creates an index on the Events table which can be useful even without joining. For example, would the following query benefit from the FK?
SELECT * FROM Events
WHERE ColA='foo' AND ColB='bar'
Note: I have run the POSTGRES EXPLAIN for a very similar case to this, and see that the query will result in a full table scan. I am not sure if this is because the FK is not helpful for this query, or if my data size is small and a scan is more efficient at my current scale.
PostgreSQL does not automatically create an index on the columns on which a foreign key is defined. If you need such an index, you will have to create it yourself.
It is usually a good idea to have such an index, so that modifications on the parent table that affect the referenced columns are efficient.