I have an html table that is filled from a DynamoDB table. Clicking a row pops up an edit form in a modal. The data inputted is sent to a flask server to update the item - using AWS DynamoDB - that was edited in the modal form. Upon reading the AWS documentation for this, the correct method is to use update_item. However, when doing so the item is added again instead of updating the item. I used the AWS here to script the below. In my DynamoDB table, the primary partition key is KEY1 and the primary sort key is KEY2 in the below reference.
table = dynamodb.Table('table_name') #define DynamoDB table
key1 = account_id #string value of account id
key2 = request.form["KEY2"] #this is a read only field in the form, so the key does not get updated here
form_val1 = request.form["input1"]
form_val2 = request.form["input2"]
form_val3 = request.form["input3"]
form_val4 = request.form["input4"]
form_val5 = request.form["input5"]
form_val6 = request.form["input6"]
form_val7 = request.form["input7"]
form_val8 = request.form["input8"]
form_val9 = request.form["input9"]
#update item in dynamo
table.update_item(
Key={
'KEY1': key1, #partition key
'KEY2': key2 #sort key
},
UpdateExpression='SET dbField1 = :val1, dbField2 = :val2, dbField3 = :val3, dbField4 = :val4, dbField5 = :val5, dbField6 = :val6, dbField7 = :val7, dbField8 = :val8, dbField9 = :val9',
ExpressionAttributeValues={
':val1': form_val1,
':val2': form_val2,
':val3': form_val3,
':val4': form_val4,
':val5': form_val5,
':val6': form_val6,
':val7': form_val7,
':val8': form_val8,
':val9': form_val9
}
)
You can't and I will explain to you for what that not is possible.
When you create a table on dynamo DB with key and a order key you automatically create an index between key and sort key. We know an index is inmutable, that means you can't update the keys. Is for that reason that when you update dynamo create a new element.
It's a problem of the definition of your table because you never need to change the key or the sort key. Recreate your table only with the index and not with the sort index (because if your app can change the sort index that make not sense).
Is this the full query? the update_item docs say that TableName is required, which I don't see in your snippet.
From the updateitem docs:
Edits an existing item's attributes, or adds a new item to the table
if it does not already exist.
Make sure that the primary key (partition key and sort key) are unique in your table. If they are not, updateitem will create a new item in the database.
Are you absolutely certain that the primary key for the item already exists in the database?
Related
I just started to study the clickhouse! I use python and library clickhouse_connect. Can't get to add a new string to the Array(String)
I try to create new String to Array
My code:
import clickhouse_connect
ch_client = clickhouse_connect.get_client(host=ch_host, user=ch_user, password=ch_pass, database=ch_datebase)
ch_client.command(f'CREATE TABLE IF NOT EXISTS {ch_table} (key String, strings Array(String)) ENGINE MergeTree ORDER BY key')
insert_data = [['123', ['string1']]]
ch_client.insert(ch_table, insert_data, column_names=['key', 'strings'])
insert_data = [['123', ['string2']]]
ch_client.insert(ch_table, insert_data, column_names=['key', 'strings'])
Is there an easy way to insert a new row into the list if there is already such a key, and if there is no such key, then create a new row?
You could just insert your rows, then write a query that gives you what you want:
SELECT
key,
groupArrayArray(strings)
FROM ch_table
GROUP BY key;
If that works, you could create a materialized view from this query:
CREATE MATERIALIZED VIEW ch_table_view
ENGINE = AggregatingMergeTree
ORDER BY key
POPULATE AS
SELECT
key,
groupArrayArrayState(strings) AS strings_merged
FROM ch_table
GROUP BY key;
Notice the -State aggregate combinator was used, which keeps a "running total" of the array of strings. To read this column, you need to use the corresponding -Merge combinator:
SELECT
key,
groupArrayArrayMerge(strings_merged)
FROM ch_table_view
GROUP BY key;
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 shifting my database from mongodb to dynamo db. I have a problem with delete function from a table where labName is partition key and serialNumber is my sort key and there is one Id as feedId I want to delete all the records from the table where labName is given and feedId is NOT IN (array of ids).
I am doing it in mongo like below mentioned code
Is there a way with BatchWriteItem where i can add condition for feedId without sort key.
let dbHandle = await getMongoDbHandle(dbName);
let query = {
feedid: {$nin: feedObjectIds}
}
let output = await dbModule.removePromisify(dbHandle,
dbModule.collectionNames.feeds, query);
While working with DynamoDB, you can perform Conditional Retrieval (GET) / Deletion (DELETE) on the records only & only if you have provided all of the attributes for the Primary Key. For example:
For a Simple Primary key, you only need to provide a value for the Partition key.
For a Composite Primary Key, you must need to provide values for both the Partition key & sort key.
I want to create a table in cassandra, that is used as a lookup table. I have a lot of urls in my database and want to store ids instead of the urls-strings. So my approach is, to store the urls in a table with two columns: id (int) and url (text).
My problem is, that I need an index for the url field and also for the id field.
The first index is used during progressing new ulrs (so find an id for an url in the database) and the second index is use during displaying data (get the url for an id).
How can I implement that in cassandra?
I would suggest creating 2 separate tables for this:
CREATE TABLE id_url (id int primary key, url text);
and
CREATE TABLE url_id (url text primary key, id int);
Inserts to these tables should be done with a batch:
BEGIN BATCH
INSERT INTO id_url (id, url) VALUES (1, '<url1>');
INSERT INTO url_id (url, id) VALUES ('<url1>', 1);
APPLY BATCH
You could create your table like this:
CREATE TABLE urls_table(
id int PRIMARY KEY,
url text
);
and then create an index on the second column:
create index urls_table_url on urls_table (url);
Your first query is satisfied since you're querying over partition key. The second one is satisfied since you created an index on url column.
In my cassandra table i have a collection of Map also i have indexed the map keys.
CREATE TABLE IF NOT EXISTS test.collection_test(
name text,
year text,
attributeMap map<text,text>,
PRIMARY KEY ((name, year))
);
CREATE INDEX ON collection_test (attributeMap);
The QueryBuilder syntax is as below:
select().all().from("test", "collection_test")
.where(eq("name", name)).and(eq("year", year));
How should i put where condition on attributeMap?
First of all, you will need to create an index on the keys in your map. By default, an index created on a map indexes the values of the map, not the keys. There is special syntax to index the keys:
CREATE INDEX attributeKeyIndex ON collection_test (KEYS(attributeMap));
Next, to SELECT from a map with indexed keys, you'll need the CONTAINS KEY keyword. But currently, there is not a definition for this functionality in the query builder API. However, there is an open ticket to support it: JAVA-677
Currently, to accomplish this with the Java Driver, you'll need to build your own query or use a prepared statement:
PreparedStatement statement = _session.prepare("SELECT * " +
"FROM test.collection_test " +
"WHERE attributeMap CONTAINS KEY ?");
BoundStatement boundStatement = statement.bind(yourKeyValue);
ResultSet results = _session.execute(boundStatement);
Finally, you should read through the DataStax doc on When To Use An Index. Secondary indexes are known to not perform well. I can't imagine that a secondary index on a collection would be any different.