When i create a table with pk field as identity and i run a script with test rows of data the sequence is out of sync
ex:
ID NUMBER(11) GENERATED BY DEFAULT ON NULL AS IDENTITY, CONSTRAINT test_id_pk PRIMARY KEY(ID),
text VARCHAR2(20)
);
INSERT INTO test VALUES(1,'asd');
INSERT INTO test VALUES(2,'asd');
INSERT INTO test VALUES(3,'asd');
INSERT INTO test VALUES(4,'asd');
INSERT INTO test VALUES(5,'asd');
INSERT INTO test VALUES(6,'asd');
then when i do
SELECT "autogenerated sequence".nextval FROM DUAL;
the result is 1
is there a way to sync all sequences?
for the moment ill have to change the pk fields of my test script to NULL, so the sequence is not out of sync
Use the following command to sync the sequence with existing data:
ALTER TABLE test MODIFY id
GENERATED BY DEFAULT ON NULL AS IDENTITY (START WITH LIMIT VALUE);
The START WITH LIMIT VALUE clause will set the sequence to the highest value of the existing data in the column, plus one.
Related
I am trying to simply insert JSON data in to a PostgreSQL database. The first column is a serial ID primary key column. When I try to insert the data and omit the serial id value, the serial id value is populated with my first record instead of automatically populating itself.
Example:
CREATE TABLE test (
id SERIAL PRIMARY KEY,
prem_id text,
name text)
Coming from JSON pipeline:
INSERT INTO test VALUES ('1001','Lucy');
INSERT INTO test VALUES ('1002','Johnny');
Table populates as follows:
id | prem_id | name
1001 | Lucy | null
1002 | Johnny | null
If I directly insert from pgAdmin, then I get the same results as above. The only time it works properly is if I add the DEFAULT keyword to the INSERT statement. Just doesn't make sense... All documentation I have read says if you omit this, then it should automatically increment.
I also tried
CREATE TABLE test (
id INT PRIMARY KEY GENERATED ALWAYS AS IDENTITY,
...)
But I am getting a syntax error "at or before GENERATED". I'm really stuck on this one.
Anyone else experience this issue or have any fixes for it?
Much appreciated!
You need to specify the target columns, otherwise the values are matched in the order the columns were defined in the CREATE TABLE statement. You also missed the VALUES clause:
INSERT INTO test
(prem_id, name)
values
('1001','Lucy'),
('1002','Johnny');
Online example
I have a postgres database with a single table. The primary key of this table is a generated UUID. I am trying to add a logging table to this database such that whenever a row is added or deleted, the logging table gets an entry. My table has the following structure
CREATE TABLE configuration (
id uuid NOT NULL DEFAULT uuid_generate_v4(),
name text,
data json
);
My logging table has the following structure
CREATE TABLE configuration_log (
configuration_id uuid,
new_configuration_data json,
old_configuration_data json,
"user" text,
time timestamp
);
I have added the following rules:
CREATE OR REPLACE RULE log_configuration_insert AS ON INSERT TO "configuration"
DO INSERT INTO configuration_log VALUES (
NEW.id,
NEW.data,
'{}',
current_user,
current_timestamp
);
CREATE OR REPLACE RULE log_configuration_update AS ON UPDATE TO "configuration"
WHERE NEW.data::json::text != OLD.data::json::text
DO INSERT INTO configuration_log VALUES (
NEW.id,
NEW.data,
OLD.data,
current_user,
current_timestamp
);
Now, if I insert a value in the configuration table, the UUID in the configuration table and the configuration_log table are different. For example, the insert query
INSERT INTO configuration (name, data)
VALUES ('test', '{"property1":"value1"}')
The result is this... the UUID is c2b6ca9b-1771-404d-baae-ae2ec69785ac in the configuration table whereas in the configuration_log table the result is this... the UUID id 16109caa-dddc-4959-8054-0b9df6417406
However, the update rule works as expected. So if I write an update query as
UPDATE "configuration"
SET "data" = '{"property1":"abcd"}'
WHERE "id" = 'c2b6ca9b-1771-404d-baae-ae2ec69785ac';
The configuration_log table gets the correct UUID as seen here i.e. c2b6ca9b-1771-404d-baae-ae2ec69785ac
I am using NEW.id in both the rules so I was expecting the same behavior. Can anyone point out what I might be doing wrong here?
Thanks
This is another good example why rules should be avoided
Quote from the manual:
For any reference to NEW, the target list of the original query is searched for a corresponding entry. If found, that entry's expression replaces the reference.
So NEW.id is replaced with uuid_generate_v4() which explains why you are seeing a different value.
You should rewrite this to a trigger.
Btw: using jsonb is preferred over json, then you can also get rid of the (essentially incorrect) cast of the json column to text to compare the content.
I am new in PostgreSQL and I am working with this database.
I got a file which I imported, and I am trying to get rows with a certain ID. But the ID is not defined, as you can see it in this picture:
so how do I access this ID? I want to use an SQL command like this:
SELECT * from table_name WHERE ID = 1;
If any order of rows is ok for you, just add a row number according to the current arbitrary sort order:
CREATE SEQUENCE tbl_tbl_id_seq;
ALTER TABLE tbl ADD COLUMN tbl_id integer DEFAULT nextval('tbl_tbl_id_seq');
The new default value is filled in automatically in the process. You might want to run VACUUM FULL ANALYZE tbl to remove bloat and update statistics for the query planner afterwards. And possibly make the column your new PRIMARY KEY ...
To make it a fully fledged serial column:
ALTER SEQUENCE tbl_tbl_id_seq OWNED BY tbl.tbl_id;
See:
Creating a PostgreSQL sequence to a field (which is not the ID of the record)
What you see are just row numbers that pgAdmin displays, they are not really stored in the database.
If you want an artificial numeric primary key for the table, you'll have to create it explicitly.
For example:
CREATE TABLE mydata (
id integer GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
obec text NOT NULL,
datum timestamp with time zone NOT NULL,
...
);
Then to copy the data from a CSV file, you would run
COPY mydata (obec, datum, ...) FROM '/path/to/csvfile' (FORMAT 'csv');
Then the id column is automatically filled.
I thought this would be simple, but I can't seem to use AUTO_INCREMENT in my db2 database. I did some searching and people seem to be using "Generated by Default", but this doesn't work for me.
If it helps, here's the table I want to create with the sid being auto incremented.
create table student(
sid integer NOT NULL <auto increment?>
sname varchar(30),
PRIMARY KEY (sid)
);
Any pointers are appreciated.
You're looking for is called an IDENTITY column:
create table student (
sid integer not null GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 1)
,sname varchar(30)
,PRIMARY KEY (sid)
);
A sequence is another option for doing this, but you need to determine which one is proper for your particular situation. Read this for more information comparing sequences to identity columns.
You will have to create an auto-increment field with the sequence object (this object generates a number sequence).
Use the following CREATE SEQUENCE syntax:
CREATE SEQUENCE seq_person
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10
The code above creates a sequence object called seq_person, that starts with 1 and will increment by 1. It will also cache up to 10 values for performance. The cache option specifies how many sequence values will be stored in memory for faster access.
To insert a new record into the "Persons" table, we will have to use the nextval function (this function retrieves the next value from seq_person sequence):
INSERT INTO Persons (P_Id,FirstName,LastName)
VALUES (seq_person.nextval,'Lars','Monsen')
The SQL statement above would insert a new record into the "Persons" table. The "P_Id" column would be assigned the next number from the seq_person sequence. The "FirstName" column would be set to "Lars" and the "LastName" column would be set to "Monsen".
hi If you are still not able to make column as AUTO_INCREMENT while creating table. As a work around first create table that is:
create table student(
sid integer NOT NULL
sname varchar(30),
PRIMARY KEY (sid)
);
and then explicitly try to alter column bu using the following
alter table student alter column sid set GENERATED BY DEFAULT AS
IDENTITY
Or
alter table student alter column sid set GENERATED BY DEFAULT
AS IDENTITY (start with 100)
Added a few optional parameters for creating "future safe" sequences.
CREATE SEQUENCE <NAME>
START WITH 1
INCREMENT BY 1
NO MAXVALUE
NO CYCLE
CACHE 10;
I have the following table in postgres:
CREATE TABLE "test" (
"id" serial NOT NULL PRIMARY KEY,
"value" text
)
I am doing following insertions:
insert into test (id, value) values (1, 'alpha')
insert into test (id, value) values (2, 'beta')
insert into test (value) values ('gamma')
In the first 2 inserts I am explicitly mentioning the id. However the table's auto increment pointer is not updated in this case. Hence in the 3rd insert I get the error:
ERROR: duplicate key value violates unique constraint "test_pkey"
DETAIL: Key (id)=(1) already exists.
I never faced this problem in Mysql in both MyISAM and INNODB engines. Explicit or not, mysql always update autoincrement pointer based on the max row id.
What is the workaround for this problem in postgres? I need it because I want a tighter control for some ids in my table.
UPDATE:
I need it because for some values I need to have a fixed id. For other new entries I dont mind creating new ones.
I think it may be possible by manually incrementing the nextval pointer to max(id) + 1 whenever I am explicitly inserting the ids. But I am not sure how to do that.
That's how it's supposed to work - next_val('test_id_seq') is only called when the system needs a value for this column and you have not provided one. If you provide value no such call is performed and consequently the sequence is not "updated".
You could work around this by manually setting the value of the sequence after your last insert with explicitly provided values:
SELECT setval('test_id_seq', (SELECT MAX(id) from "test"));
The name of the sequence is autogenerated and is always tablename_columnname_seq.
In the recent version of Django, this topic is discussed in the documentation:
Django uses PostgreSQL’s SERIAL data type to store auto-incrementing
primary keys. A SERIAL column is populated with values from a sequence
that keeps track of the next available value. Manually assigning a
value to an auto-incrementing field doesn’t update the field’s
sequence, which might later cause a conflict.
Ref: https://docs.djangoproject.com/en/dev/ref/databases/#manually-specified-autoincrement-pk
There is also management command manage.py sqlsequencereset app_label ... that is able to generate SQL statements for resetting sequences for the given app name(s)
Ref: https://docs.djangoproject.com/en/dev/ref/django-admin/#django-admin-sqlsequencereset
For example these SQL statements were generated by manage.py sqlsequencereset my_app_in_my_project:
BEGIN;
SELECT setval(pg_get_serial_sequence('"my_project_aaa"','id'), coalesce(max("id"), 1), max("id") IS NOT null) FROM "my_project_aaa";
SELECT setval(pg_get_serial_sequence('"my_project_bbb"','id'), coalesce(max("id"), 1), max("id") IS NOT null) FROM "my_project_bbb";
SELECT setval(pg_get_serial_sequence('"my_project_ccc"','id'), coalesce(max("id"), 1), max("id") IS NOT null) FROM "my_project_ccc";
COMMIT;
It can be done automatically using a trigger. This way you are sure that the largest value is always used as the next default value.
CREATE OR REPLACE FUNCTION set_serial_id_seq()
RETURNS trigger AS
$BODY$
BEGIN
EXECUTE (FORMAT('SELECT setval(''%s_%s_seq'', (SELECT MAX(%s) from %s));',
TG_TABLE_NAME,
TG_ARGV[0],
TG_ARGV[0],
TG_TABLE_NAME));
RETURN OLD;
END;
$BODY$
LANGUAGE plpgsql;
CREATE TRIGGER set_mytable_id_seq
AFTER INSERT OR UPDATE OR DELETE
ON mytable
FOR EACH STATEMENT
EXECUTE PROCEDURE set_serial_id_seq('mytable_id');
The function can be reused for multiple tables. Change "mytable" to the table of interest.
For more info regarding triggers:
https://www.postgresql.org/docs/9.1/plpgsql-trigger.html
https://www.postgresql.org/docs/9.1/sql-createtrigger.html