I have two userdefined type in Cassandra. First one is using the second object as frozen object inside it.
CREATE TYPE my_keyspace.test (
testid text,
testdate text,
testdata frozen<testdata>
);
CREATE TYPE my_keyspace.testdata (
subject text,
metadata text
);
Now my requirement is to convert this single object to list of UDT . Something like this
CREATE TYPE my_keyspace.test (
testid text,
testdate text,
testdata list<frozen<testdata>>
);
Is it possible to update single object to list of object in Cassandra. Whata are options available to update the schema.
The only way to do it, is to add another field with required type using the ALTER TYPE, and start to use this new field, migrating existing data using some code. Cassandra doesn't allow to change type of the existing fields, and you can't also drop a field from UDT. So your type should be something like this:
CREATE TYPE my_keyspace.test (
testid text,
testdate text,
testdata frozen<testdata>
testdata_lst list<frozen<testdata>>
);
Existing data could be migrated into a list, and then set to null to free the space.
Related
From what I looked so far, it seems impossible with Cassandra. But I thought I'd give it a shot:
How can I select a value of a json property, parsed from a json object string, and use it as part of an update / insert statement in Cassandra?
For example, I'm given the json object:
{
id:123,
some_string:"hello there",
mytimestamp: "2019-09-02T22:02:24.355Z"
}
And this is the table definition:
CREATE TABLE IF NOT EXISTS myspace.mytable (
id text,
data blob,
PRIMARY KEY (id)
);
Now the thing to know at this point is that for a given reason the data field will be set to the json string. In other words, there is no 1:1 mapping between the given json and the table columns, but the data field contains the json object as kind of a blob value.
... Is it possible to parse the timestamp value of the given json object as part of an insert statement?
Pseudo code example of what I mean, which obviously doesn't work ($myJson is a placeholder for the json object string above):
INSERT INTO myspace.mytable (id, data)
VALUES (123, $myJson)
USING timestamp toTimeStamp($myJson.mytimestamp)
The quick answer is no, it's not possible to do that with CQL.
The norm is to parse the elements of the JSON object within your application to extract the corresponding values to construct the CQL statement.
As a side note, I would discourage using the CQL blob type due to possible performance issues should the blob size exceeed 1MB. If it's JSON, consider storing it as CQL text type instead. Cheers!
Worth mentioning, but CQL can do a limited amount of JSON parsing on its own. Albeit, not as detailed as you're asking here (ex: USING timestamp).
But something like this works:
> CREATE TABLE myjsontable (
... id TEXT,
... some_string TEXT,
... PRIMARY KEY (id));
> INSERT INTO myjsontable JSON '{"id":"123","some_string":"hello there"}';
> SELECT * FROM myjsontable WHERE id='123';
id | some_string
-----+-------------
123 | hello there
(1 rows)
In your case you'd either have to redesign the table or the JSON payload so that they match. But as Erick and Cédrick have mentioned, the USING timestamp part would have to happen client-side.
What you detailed is doable with Cassandra.
Timestamp
To insert timestamp in a query it should be formatted as an ISO 8601 String. Sample examples could be found here. In your code, you might have to convert your incoming value to expected type and format.
Blob:
Blob expects to store binary data, as such it cannot be put Ad hoc as a String in a CQL query. (you can use TEXT type to do it if you want to encode base64)
When you need to insert binary data you need to provide proper type as well. For instance if you are working with Javascript to need to provide a Buffer as describe in the documentation Then when you execute your query you externalized your parameters
const sampleId = 123;
const sampleData = Buffer.from('hello world', 'utf8');
const sampleTimeStamp = new Date();
client.execute('INSERT INTO myspace.mytable (id, data) VALUES (?, ?) USING timestamp toTimeStamp(?)', [ sampleId, sampleData, sampleTimeStamp ]);
Im currently working on creating correct database columns for my database. I have created two tables and used alter:
CREATE TABLE stores (
id SERIAL PRIMARY KEY,
store_name TEXT
-- add more fields if needed
);
CREATE TABLE products (
id SERIAL,
store_id INTEGER NOT NULL,
title TEXT,
image TEXT,
url TEXT UNIQUE,
added_date timestamp without time zone NOT NULL DEFAULT NOW(),
PRIMARY KEY(id, store_id)
);
ALTER TABLE products
ADD CONSTRAINT "FK_products_stores" FOREIGN KEY ("store_id")
REFERENCES stores (id) MATCH SIMPLE
ON UPDATE NO ACTION
ON DELETE RESTRICT;
Now I am trying to use it together with PeeWee and I have managed to do a small step which is:
class Stores(Model):
id = IntegerField(column_name='id')
store_id = TextField(column_name='store_name')
class Products(Model):
id = IntegerField(column_name='id')
store_id = IntegerField(column_name='store_id')
title = TextField(column_name='title')
url = TextField(column_name='url')
image = TextField(column_name='image')
However my problem is that I have used:
ALTER TABLE products
ADD CONSTRAINT "FK_products_stores" FOREIGN KEY ("store_id")
REFERENCES stores (id) MATCH SIMPLE
ON UPDATE NO ACTION
ON DELETE RESTRICT;
which means that I do have a Foreign key and I am quite not sure how I can apply to use Foreign key together with PeeWee. I wonder how can I do that?
You need to add a ForeignKeyField to Products and remove store_id
class Products(Model):
id = IntegerField(column_name='id')
title = TextField(column_name='title')
url = TextField(column_name='url')
image = TextField(column_name='image')
store = ForeignKeyField(Stores, backref='products')
I am building an API server which accepts file uploads using multer.
I need to store an array of all the paths to all files uploaded for each request to a column in the PostgreSQL database which I have connected to the server.
Say I have a table created with the following query
CREATE TABLE IF NOT EXISTS records
(
id SERIAL PRIMARY KEY,
created_on TIMESTAMPTZ NOT NULL DEFAULT NOW(),
created_by INTEGER,
title VARCHAR NOT NULL,
type VARCHAR NOT NULL
)
How do I define a new column filepaths on the above table where I can insert a javascript string array (ex: ['path-to-file-1', 'path-to-file-2', 'path-to-file-3']).
Also how do I retrive, update/edit the list in javascript using node-postgres
You have 2 options:
use json or jsonb type. In the case string to insert will look:
'["path-to-file-1", "path-to-file-2", "path-to-file-3"]'
I would prefer jsonb - it allows to have good indexes. Json is rather just text with some additional built-in functions.
Use array of text - something like filepaths text[]. To insert you can use:
ARRAY ['path-to-file-1', 'path-to-file-2', 'path-to-file-3']
or
'{path-to-file-1,path-to-file-2,path-to-file-3,"path to file 4"}'
You need to use " here only for elements that contain space and so on. But you fill free to use it for all elements too.
You can create a file table that has a path column and a foreign key reference to the record that it belongs to. This way you can store the path as just a text column instead of storing an array in a column, which is better practice for relational databases. You'll also be able to store additional information on a file if you need to later. And it'll be more simple to interact with the file path records since you'd add a new file path by just inserting a new row into the file table (with the appropriate foreign key) and remove by deleting a row from the file table.
For example:
CREATE TABLE IF NOT EXISTS file (
record_id integer NOT NULL REFERENCES records(id) ON DELETE CASCADE,
path text NOT NULL
);
Then to get all the files for a record you can join the two tables together and convert to an array if you want.
For example:
SELECT
records.*,
ARRAY (
SELECT
file.path
FROM
file
WHERE
records.id = file.record_id
) AS file_paths
FROM
records;
Sample input (using only the title field of records):
INSERT INTO records (title) VALUES ('A'), ('B'), ('C');
INSERT INTO file (record_id, path) VALUES (1, 'patha1'), (1, 'patha2'), (1, 'patha3'), (2, 'pathb1');
Sample output:
id | title | file_paths
----+-------+------------------------
1 | A | {patha1,patha2,patha3}
2 | B | {pathb1}
3 | C | {}
I have following requirement of my dataset, need to unserstand what datatype should I use and how to save my data accordingly :-
CREATE TABLE events (
id text,
evntoverlap map<text, map<timestamp,int>>,
PRIMARY KEY (id)
)
evntoverlap = {
'Dig1': {{'2017-10-09 04:10:05', 0}},
'Dig2': {{'2017-10-09 04:11:05', 0},{'2017-10-09 04:15:05', 0}},
'Dig3': {{'2017-10-09 04:11:05', 0},{'2017-10-09 04:15:05', 0},{'2017-10-09 04:11:05', 0}}
}
This gives an error :-
Error from server: code=2200 [Invalid query] message="Non-frozen collections are not allowed inside collections: map<text, map<timestamp, int>>"
How should I store this type of data in single column . Please suggest datatype and insert command for the same.
Thanks,
There is limitation of Cassandra - you can't nest collection (or UDT) inside collection without making it frozen. So you need to "froze" one of the collections - either nested:
CREATE TABLE events (
id text,
evntoverlap map<text, frozen<map<timestamp,int>>>,
PRIMARY KEY (id)
);
or top-level:
CREATE TABLE events (
id text,
evntoverlap frozen<map<text, map<timestamp,int>>>,
PRIMARY KEY (id)
);
See documentation for more details.
CQL collections limited to 64kb, if putting things like maps in maps you might push that limit. Especially with frozen maps you are deserializing the entire map, modifying it, and re inserting. Might be better off with a
CREATE TABLE events (
id text,
evnt_key, text
value map<timestamp, int>,
PRIMARY KEY ((id), evnt_key)
)
Or even a
CREATE TABLE events (
id text,
evnt_key, text
evnt_time timestamp
value int,
PRIMARY KEY ((id), evnt_key, evnt_time)
)
It would be more efficient and safer while giving additional benefits like being able to order the event_time's in ascending or descending order.
I am trying to insert values in UDT but getting error message -
message="unconfigured columnfamily my_object"
below my statement-
INSERT INTO home.my_object (id,type,quantity ,critical,page_count,stock,outer_envelope ) VALUES ('3.MYF','COM','D','A','VV','','');
What am i doing wrong?
That error means that the keyspace "home" exists, but does not contain a table (column family) called "my_object". I also noticed that your insert statement does not contain a UDT literal.
UDTs define a type, but you must also define a table with a column of that type before inserting any data. I assume your UDT is called "my_object". Try this:
create table home.test (key int primary key, object frozen<my_object>);
insert into home.test (key, object) values (0, {id: 'value', type: 'othervalue'});