I drop not null on primary key column, and it executes, after I check schema of table and there is not null
table:
-- auto-generated definition
create table warehouses
(
id_warehouse serial not null
constraint warehouse_pkey
primary key,
responsible_person varchar(30) not null
);
script to drop not null:
alter table warehouses
drop constraint warehouse_pkey;
alter table warehouses
alter id_warehouse drop not null;
alter table warehouses
add constraint warehouse_pkey
primary key (id_warehouse);
Per information here:
https://www.postgresql.org/docs/current/sql-createtable.html
PRIMARY KEY (column constraint)
The PRIMARY KEY constraint specifies that a column or columns of a table can contain only unique (non-duplicate), nonnull values. Only one primary key can be specified for a table, whether as a column constraint or a table constraint.
A column defined as PRIMARY KEY will also have the NOT NULL constraint set.
Related
Trying to create this example table structure in Postgres 9.1:
CREATE TABLE foo (
name VARCHAR(256) PRIMARY KEY
);
CREATE TABLE bar (
pkey SERIAL PRIMARY KEY,
foo_fk VARCHAR(256) NOT NULL REFERENCES foo(name),
name VARCHAR(256) NOT NULL,
UNIQUE (foo_fk,name)
);
CREATE TABLE baz(
pkey SERIAL PRIMARY KEY,
bar_fk VARCHAR(256) NOT NULL REFERENCES bar(name),
name VARCHAR(256)
);
Running the above code produces an error, which does not make sense to me:
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "foo_pkey" for table "foo"
NOTICE: CREATE TABLE will create implicit sequence "bar_pkey_seq" for serial column "bar.pkey"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "bar_pkey" for table "bar"
NOTICE: CREATE TABLE / UNIQUE will create implicit index "bar_foo_fk_name_key" for table "bar"
NOTICE: CREATE TABLE will create implicit sequence "baz_pkey_seq" for serial column "baz.pkey"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "baz_pkey" for table "baz"
ERROR: there is no unique constraint matching given keys for referenced table "bar"
********** Error **********
ERROR: there is no unique constraint matching given keys for referenced table "bar"
SQL state: 42830
Can anyone explain why this error arises?
It's because the name column on the bar table does not have the UNIQUE constraint.
So imagine you have 2 rows on the bar table that contain the name 'ams' and you insert a row on baz with 'ams' on bar_fk, which row on bar would it be referring since there are two rows matching?
In postgresql all foreign keys must reference a unique key in the parent table, so in your bar table you must have a unique (name) index.
See also http://www.postgresql.org/docs/9.1/static/ddl-constraints.html#DDL-CONSTRAINTS-FK and specifically:
Finally, we should mention that a foreign key must reference columns
that either are a primary key or form a unique constraint.
Emphasis mine.
You should have name column as a unique constraint. here is a 3 lines of code to change your issues
First find out the primary key constraints by typing this code
\d table_name
you are shown like this at bottom "some_constraint" PRIMARY KEY, btree (column)
Drop the constraint:
ALTER TABLE table_name DROP CONSTRAINT some_constraint
Add a new primary key column with existing one:
ALTER TABLE table_name ADD CONSTRAINT some_constraint PRIMARY KEY(COLUMN_NAME1,COLUMN_NAME2);
That's All.
when you do UNIQUE as a table level constraint as you have done then what your defining is a bit like a composite primary key see ddl constraints, here is an extract
This specifies that the combination of values in the indicated columns is unique across the whole table, though any one of the columns need not be (and ordinarily isn't) unique.
this means that either field could possibly have a non unique value provided the combination is unique and this does not match your foreign key constraint.
most likely you want the constraint to be at column level. so rather then define them as table level constraints, 'append' UNIQUE to the end of the column definition like name VARCHAR(60) NOT NULL UNIQUE or specify indivdual table level constraints for each field.
Trying to create this example table structure in Postgres 9.1:
CREATE TABLE foo (
name VARCHAR(256) PRIMARY KEY
);
CREATE TABLE bar (
pkey SERIAL PRIMARY KEY,
foo_fk VARCHAR(256) NOT NULL REFERENCES foo(name),
name VARCHAR(256) NOT NULL,
UNIQUE (foo_fk,name)
);
CREATE TABLE baz(
pkey SERIAL PRIMARY KEY,
bar_fk VARCHAR(256) NOT NULL REFERENCES bar(name),
name VARCHAR(256)
);
Running the above code produces an error, which does not make sense to me:
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "foo_pkey" for table "foo"
NOTICE: CREATE TABLE will create implicit sequence "bar_pkey_seq" for serial column "bar.pkey"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "bar_pkey" for table "bar"
NOTICE: CREATE TABLE / UNIQUE will create implicit index "bar_foo_fk_name_key" for table "bar"
NOTICE: CREATE TABLE will create implicit sequence "baz_pkey_seq" for serial column "baz.pkey"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "baz_pkey" for table "baz"
ERROR: there is no unique constraint matching given keys for referenced table "bar"
********** Error **********
ERROR: there is no unique constraint matching given keys for referenced table "bar"
SQL state: 42830
Can anyone explain why this error arises?
It's because the name column on the bar table does not have the UNIQUE constraint.
So imagine you have 2 rows on the bar table that contain the name 'ams' and you insert a row on baz with 'ams' on bar_fk, which row on bar would it be referring since there are two rows matching?
In postgresql all foreign keys must reference a unique key in the parent table, so in your bar table you must have a unique (name) index.
See also http://www.postgresql.org/docs/9.1/static/ddl-constraints.html#DDL-CONSTRAINTS-FK and specifically:
Finally, we should mention that a foreign key must reference columns
that either are a primary key or form a unique constraint.
Emphasis mine.
You should have name column as a unique constraint. here is a 3 lines of code to change your issues
First find out the primary key constraints by typing this code
\d table_name
you are shown like this at bottom "some_constraint" PRIMARY KEY, btree (column)
Drop the constraint:
ALTER TABLE table_name DROP CONSTRAINT some_constraint
Add a new primary key column with existing one:
ALTER TABLE table_name ADD CONSTRAINT some_constraint PRIMARY KEY(COLUMN_NAME1,COLUMN_NAME2);
That's All.
when you do UNIQUE as a table level constraint as you have done then what your defining is a bit like a composite primary key see ddl constraints, here is an extract
This specifies that the combination of values in the indicated columns is unique across the whole table, though any one of the columns need not be (and ordinarily isn't) unique.
this means that either field could possibly have a non unique value provided the combination is unique and this does not match your foreign key constraint.
most likely you want the constraint to be at column level. so rather then define them as table level constraints, 'append' UNIQUE to the end of the column definition like name VARCHAR(60) NOT NULL UNIQUE or specify indivdual table level constraints for each field.
I am trying to create a database with minimum redundancy in mind. We would like to use the timescaledb hypertables (I run postgreSQL v. 12 and timescaledb v. 1.7.4). The postgreSQL code to create the tables are as follows - you can see the dbdiagram here https://dbdiagram.io/d/5f992f0e3a78976d7b797ca2 or view the tables here Image of database
CREATE TABLE "datapoints" (
"id" bigserial UNIQUE NOT NULL,
"tstz" timestamptz NOT NULL,
"entity_id" bigint NOT NULL,
"value" real NOT NULL,
PRIMARY KEY ("tstz", "entity_id")
);
CREATE TABLE "datapoint_quality" (
"tstz" timestamptz NOT NULL,
"datapoint_id" bigint NOT NULL,
"flag_id" bigint NOT NULL,
PRIMARY KEY ("tstz", "datapoint_id", "flag_id")
);
CREATE TABLE "quality_flags" (
"id" bigserial PRIMARY KEY,
"value" text
);
CREATE TABLE "sensor_types" (
"id" bigserial PRIMARY KEY,
"name" text UNIQUE NOT NULL
);
CREATE TABLE "sensors" (
"tstz" timestamptz NOT NULL DEFAULT (now()),
"id" bigserial UNIQUE NOT NULL,
"name" text NOT NULL,
"parent" bigint NOT NULL,
"type" bigint NOT NULL,
PRIMARY KEY ("tstz", "id")
);
CREATE TABLE "datapoint_annotation" (
"tstz" timestamptz NOT NULL,
"datapoint_id" bigint NOT NULL,
"annotation_id" bigint NOT NULL,
PRIMARY KEY ("tstz", "datapoint_id", "annotation_id")
);
CREATE TABLE "annotations" (
"id" bigserial PRIMARY KEY NOT NULL,
"value" text NOT NULL
);
ALTER TABLE "datapoints" ADD FOREIGN KEY ("entity_id") REFERENCES "sensors" ("id");
ALTER TABLE "datapoint_quality" ADD FOREIGN KEY ("datapoint_id") REFERENCES "datapoints" ("id");
ALTER TABLE "datapoint_quality" ADD FOREIGN KEY ("flag_id") REFERENCES "quality_flags" ("id");
ALTER TABLE "sensors" ADD FOREIGN KEY ("parent") REFERENCES "sensors" ("id");
ALTER TABLE "sensors" ADD FOREIGN KEY ("type") REFERENCES "sensor_types" ("id");
ALTER TABLE "datapoint_annotation" ADD FOREIGN KEY ("datapoint_id") REFERENCES "datapoints" ("id");
ALTER TABLE "datapoint_annotation" ADD FOREIGN KEY ("annotation_id") REFERENCES "annotations" ("id");
CREATE UNIQUE INDEX ON "quality_flags" ("value");
CREATE UNIQUE INDEX ON "annotations" ("value");
So far so good - next I want to create the hypertables, which I do as:
SELECT create_hypertable('datapoint_annotation', 'tstz');
SELECT create_hypertable('datapoint_quality', 'tstz');
SELECT create_hypertable('datapoints', 'tstz');
SELECT create_hypertable('sensors', 'tstz');
This works well for the first two lines, but for the latter two I get the following error:
ERROR: cannot create a unique index without the column "tstz" (used in partitioning)
SQL state: TS103
I can include the tstz in the primary key as ("id", "tstz") and use that as foreign key, but this gives me a one-to-one relation, and for minimum redundancy I would like to have a one-to-many relation.
I am sure there should be some way to do this - so what am I missing?
I'll take the foreign key constraint from datapoint_quality to datapoints as an example.
To make that work with a partitioned table, you need a unique constraint on datapoint. As the error message tell you, such a constraint must contain the partitioning key. So you end up with
ALTER TABLE datapoints ADD UNIQUE (id, tstz);
To reference that unique constraint from datapoint_quality, you need to have the timestamp there too:
ALTER TABLE datapoint_quality ADD datapoints_tstz timestamp with time zone;
You have to fill it with the appropriate values:
UPDATE datapoint_quality AS dq
SET datapoints_tstz = d.tstz
FROM datapoints AS d
WHERE d.id = dq.datapoint_id;
Then set it NOT NULL:
ALTER TABLE datapoint_quality ALTER datapoints_tstz SET NOT NULL;
Now you can define your foreign key:
ALTER TABLE datapoint_quality
ADD FOREIGN KEY (datapoint_id, datapoints_tstz)
REFERENCES datapoints (id, tstz) MATCH FULL;
There is no other way to have foreign key constraints with partitioned tables.
After testing the proposed solution by Laurenz in a database I have and also after replicating the original database of this case. I use PostgreSQL 12.6 and timescaledb 1.7.5.
Basically, I arrived well until defining the Foreign Key for Table datapoint_quality:
ALTER TABLE datapoint_quality
ADD FOREIGN KEY (datapoint_id, datapoints_tstz)
REFERENCES datapoints (id, tstz) MATCH FULL;
The next error is present in both databases I've tested after several attempts (included above one) to define the foreign key to a hypertable:
ERROR: foreign keys to hypertables are not supported Blockquote SQL state: 0A000
According to https://docs.timescale.com/timescaledb/latest/overview/limitations/##distributed-hypertable-limitations, it looks like the above error is part of the hypertable limitations:
Foreign key constraints referencing a hypertable are not supported.
Considering this, does anyone know any solution at the DB level to establish the relationships (1..* or ...) among a table without hypertables to other tables with hypertables behind?
Maybe could be a solution to deal with this at even a REST API level (e.g. Django or Flask) given at timescaledb or PostgreSQL I have not found much more solutions.
Existing table with 5 columns.
qid which is the PK, question geo_type user_input active
I need to be able to insert into the table with each new insert getting a new primary key id (which would be the max existing id +1).
So i need to be able to do this
insert into sip_questions (question,geo_type,user_input,active) values('noury','octagon',TRUE,TRUE)
but this give me this error
ERROR: duplicate key value violates unique constraint "s_questions_pkey"
DETAIL: Key (qid)=(1) already exists.
********** Error **********
ERROR: duplicate key value violates unique constraint "s_questions_pkey"
SQL state: 23505
Detail: Key (qid)=(1) already exists.
this is the table
CREATE TABLE public.sip_questions
(
qid integer NOT NULL DEFAULT nextval('s_questions_qid_seq'::regclass),
question character varying(200),
geo_type character varying(10),
user_input boolean,
active boolean,
CONSTRAINT s_questions_pkey PRIMARY KEY (qid)
)
WITH (
OIDS=FALSE
);
ALTER TABLE public.sip_questions
OWNER TO postgres;
i know how to do this from a fresh table like this
ALTER TABLE table ADD COLUMN id SERIAL PRIMARY KEY;
and every insert will increment the PK without me having to specify the id column
The new sequence must be bumped to the current max value.
You can reset it using
SELECT setval('s_questions_qid_seq', max(id)) FROM sip_questions;
I have been facing a problem on my django application while trying to add an value to a model. It seems that there is a constraint in the DB that should not be there, according to models.py. The error I get is:
IntegrityError: null value in column "column_x_ptr_id" violates not-null constraint
Doing a \dt in psql, I get:
Indexes:
"mytable_model_pkey" PRIMARY KEY, btree (column_x_ptr_id)
"mytable_model_p_key" UNIQUE CONSTRAINT, btree (column_y_ptr_id)
So, my question is how can I modify this index like so?
"mytable_model_pkey" PRIMARY KEY, btree (column_y_ptr_id)
I'm not sure that would solve the problem though..
Ok this will give you a "more or less" of what you need to do. Your table looks something like this:
CREATE TABLE mytable_model
(
column_x_ptr_id integer NOT NULL,
column_y_ptr_id integer,
CONSTRAINT mytable_model_pkey PRIMARY KEY (column_x_ptr_id),
CONSTRAINT mytable_model_p_key UNIQUE (column_y_ptr_id)
)
You need to drop both indexes, create a new PK on the second column, and remove the NOT NULL constraint:
ALTER TABLE mytable_model DROP CONSTRAINT mytable_model_pkey;
ALTER TABLE mytable_model DROP CONSTRAINT mytable_model_p_key;
ALTER TABLE mytable_model ADD CONSTRAINT mytable_model_pkey PRIMARY KEY (column_y_ptr_id);
ALTER TABLE mytable_model ALTER COLUMN column_x_ptr_id DROP NOT NULL;
Bear in mind that adding a primary key to column_y_ptr_id will change the column to NOT NULL. If any records have NULL in that field, this will fail. Then as I mentioned, you will probably want to put another index on column_x_ptr_id for performance reasons. What type you use is up to you.