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Im trying to build a histogram of a certain attribute in my dynamodb.
I thought the easiest way would be to use multiple filter-expression
This is my baseline query with a single filter-expression and it works
aws dynamodb scan --table-name test --select "COUNT" --filter-expression "contains(score, :s)" --expression-attribute-values '{ ":s": { "N": "1" } }' --limit 100
Now, im trying to extend it to multiple filter expressions and im not sure how.
I have tried:
aws dynamodb scan --table-name test --select "COUNT" --filter-expression "score = :s" --filter-expression "score = :s1" --expression-attribute-values '{ ":s": { "N": "1" }, ":s1": { "N": "40" } }' --limit 100
and
aws dynamodb scan --table-name test --select "COUNT" --filter-expression "score = :s" | "score = :s1" --expression-attribute-values '{ ":s": { "N": "1" }, ":s1": { "N": "40" } }' --limit 100
686
A Scan operation in Amazon DynamoDB reads every item in a table or a secondary index. By default, a Scan operation returns all of the data attributes for every item in the table or index. You can use the ProjectionExpression parameter so that Scan only returns some of the attributes, rather than all of them.
A filter expression determines which items within the Query results should be returned to you. All of the other results are discarded. A filter expression is applied after a Query finishes, but before the results are returned.
More complex queries on DynamoDB data are occasionally required. Instead of scanning for such queries, it is usually preferable to create a GSI (global secondary index). Out of interest, I ran an experiment to confirm that Scan operation is indeed slower than Query operation.
Scans are generally speaking slow. To make that process faster, you can use a feature called "Parallel Scans" which divide the whole DynamoDB Table into Segments. A separate thread/worker then processes each Segment so N workers can work simultaneously to go through the whole keyspace faster.
Probably I am late to answer. But, was searching for a similar scenario and got nothing. Still answering if someone else could benefit.
aws dynamodb scan --table-name test --select "COUNT" \
--filter-expression "score = :s OR score = :s1" \
--expression-attribute-values '{ ":s": { "N": "1" }, ":s1": { "N": "40" } }' \
--limit 100
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