I have a DynamoDB table with following keys:
id: partition key
created_at: sort key
brand#category#size#color: partition key for global index 'byAttributes'
The global index partition key is a composite of 4 table attributes using '#' as a delimiter.
Is there a way in DynamoDB that I can query the table using only a subset of the attributes using a wildcard for unspecified attributes?
As examples:
byAttributes = 'levis#shirts#*#red'
byAttributes = '*#pants#L#*'
I don't wish to use a FilterExpression because it only filters data after a search. I want to take advantage of the attributes being indexed.
No. But you can create alternative GSIs for different combinations.
You can also include a hierarchical SK value and use begins-with to limit based on zero or more values.
Putting some values in the PK and the rest in a hierarchical SK achieves a lot of combinations.
For example have a GSI:
PK = category,
SK = size#brand#color
Now you can query by category, category/size, category/size/brand, or all four.
If it gets more than four you may want to look at Rockset as an indexing system against DynamoDB data.
Related
I have a simple table consisting of orderID as PK and userID as SK, I found out that in dynamoDB you need to specify both PK and SK to use query. so in this case, how is it possible for me to get all the orders for userID x since I can't ignore orderID since they're the partition key of this table? another way to solve this which works but not recomended is using a scan filter, which scans the whole table then filters the result. it will eventually slow down as the table grow. I wonder how do you guys do it with this scenario?
You can create a Global Secondary Index (GSI) based on userId and query based on that index.
You can read more about indexes and GSI’s in the AWS docs here.
select * from tableName where columnName="value";
How can I fetch a similar result in DynamoDB using java, without using primary key as my attribute (Need to group data based on a value for a particular column).
I have gone through articles regarding getbatchitems, QuerySpec but all these require me to pass the primary key.
Can someone give a lead here?
Short answer is you can't. Whenever you use the Query or GetItem operations in DynamoDB you must always supply the table or index primary key.
You have two options:
Perform a Scan operation on the table and filter by columnName="value". However this requires DynamoDB to look at every item in the table so it is likely to be slow and expensive.
Add a Global Secondary Index to your table. This will require you to define a primary key for the index that contains the columnName you want to query
Is it possible to retrieve rows from the dynamodb Global secondary index using batchgetitem api? If my aim is to retrieve data from the main table based on some non-key attribute also , but data should be retrieved in the batch of 100 items - is the GSI index won't fit here?
Also is BatchItemGet API available for Query? Say a table has the primary key and sort key and same primary key can have multiple sort keys can I retrieve multiple primary keys using batchItemGet with just primary key only or it won't fir here?
There is no way to specify the index name in the BatchGetItem API operation according to the docs. That means using BatchGetItem (and GetItem for that matter) on a secondary index isn't possible. Both of these operate on the primary index.
If you want to retrieve data from a secondary index, you need to use Query or Scan. Both support the IndexName attribute according to the documentation. When using Query you have to specify the partition key and can optionally filter based on the sort key. If you don't filter on the sort key, you will get all items with the partition key, which should take care of your second requirement.
To retrieve data from a secondary index based on different partition keys, you'd need to issue multiple Query operations for the separate values of these keys, there is no batching here.
You can use PartiQL with WHERE IN clause for that:
SELECT * FROM Orders WHERE OrderID IN [100, 300, 234]
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ql-reference.select.html
I have 2 LSI in my table with a primary partition Key with primary sort key
Org-ID - primary partition Key
ClientID- primary sort Key
Gender - LSI
Section - LSI
I have no issue with querying a table with one LSI, but how to mention 2 LSI in a table schema.
var params = {
TableName:"MyTable",
IndexNames: ['ClientID-Gender-index','ClientID-Section-index'],
KeyConditionExpression : '#Key1 = :Value1 and #Key2=:Value2 and #Key3=:Value3',
ExpressionAttributeNames:{
"#Key1":"Org-ID",
"#Key2":"Gender",
"#Key3":"Section"
},
ExpressionAttributeValues : {
':Value1' :"Microsoft",
':Value2':"Male",
':Value3':"Cloud Computing"
}};
Can anyone fix the issue in IndexName(line 3) or KeyConditionExpression(line 4), I'm not sure about it.
Issue
Condition can be of length 1 or 2 only
You can only query a single DynamoDB index at a time. You cannot use multiple indexes in the same query.
A simple alternative is to use a single index and apply a query filter, but this will potentially require a lot of records to be scanned and the filter only reduces the amount of data transferred over the network.
A more advanced alternative is to make a compound key. You would most likely want to use a GSI, rather than an LSI for this use case. By making a single new column that is the string concatenation of Key1, Key2, and Key3 you can use this GSI to search all three keys at the same time. This will make each individual record bigger by repeating data but it allows for a more complex query pattern.
I am studying DynamoDB and confuse on the order.
a. Could I use multiple conditions in the KeyConditions field of query command to do the 'AND' query? i.e. Set condition to the following keys:
hash part of primary key,
range part of primary key,
local secondary index 1,
b. If it's workable, how would DynamoDB sort the result?
DynamoDB can only use one index at a time so you can't really query using both a range primary key AND a secondary index.
The sort will be based on the index actually used.
The conditions are filtering out results and are not limited to indices.