How to get item count from DynamoDB

Question

I want to know item count with DynamoDB querying   I can querying for DynamoDB  but I only want to know  total count of item    For example   SELECT COUNT    FROM     WHERE      in MySQL   result    aws- gt query array    TableName    gt   game table     IndexName    gt   week-point-index     KeyConditions    gt  array       week    gt  array           ComparisonOperator    gt   EQ            AttributeValueList    gt  array              array Type  STRING   gt   week                        point    gt  array           ComparisonOperator    gt   GE            AttributeValueList    gt  array              array Type  NUMBER   gt   my point                          echo Count  result  Items       this code gets the all users data higher than my point   If count of  result is 100 000   result is too much big  And it would exceed the limits of the query size   I need help

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In Scala   import com amazonaws services dynamodbv2 AmazonDynamoDBClientBuilder import com amazonaws services dynamodbv2 document DynamoDB val client   AmazonDynamoDBClientBuilder standard   build    val dynamoDB   new DynamoDB client  val tableDescription   dynamoDB getTable  table name   describe   getItemCount

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If you happen to reach here  and you are working with C   here is the code   var cancellationToken   new CancellationToken     var request   new ScanRequest  TableName    Select   Select COUNT    var result   context Client ScanAsync request  cancellationToken  Result   totalCount   result Count

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Replace the table name and use the below query to get the data on your local environment   aws dynamodb scan --table-name  lt TABLE NAME gt  --select  COUNT  --endpoint-url http   localhost 8000   Replace the table name and remove the endpoint url to get the data on production environment  aws dynamodb scan --table-name  lt TABLE NAME gt  --select  COUNT

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With the aws dynamodb cli you can get it via scan as follows   aws dynamodb scan --table-name  lt TABLE NAME gt  --select  COUNT    The response will look similar to this          Count   123       ScannedCount   123       ConsumedCapacity   null     notice that this information is in real time in contrast to the describe-table api

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I m too late here but like to extend Daniel s answer about using aws cli to include filter expression  Running aws dynamodb scan       --table-name  lt tableName gt        --filter-expression  quot  v    num quot        --expression-attribute-names    quot  v quot    quot fieldName quot          --expression-attribute-values    quot  num quot     quot N quot    quot 123 quot           --select  quot COUNT quot   would give        quot Count quot   2945       quot ScannedCount quot   7874       quot ConsumedCapacity quot   null    That is  ScannedCount is total count and Count is the number of items which are filtered by given expression  fieldName 123

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len response  Items      will give you the count of the filtered rows   where   fe   Key  entity   eq  tesla   response   table scan FilterExpression fe

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This is solution for AWS JavaScript SDK users  it is almost same for other languages   Result data Count will give you what you are looking for   apigClient getitemPost     body            then function result            var dataoutput   result data Items 0            console log result data Count        catch  function result

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I used scan to get total count of the required tableName Following is a Java code snippet for same  Long totalItemCount   0  do      ScanRequest req   new ScanRequest        req setTableName tableName        if result    null           req setExclusiveStartKey result getLastEvaluatedKey                result   client scan req        totalItemCount    result getItems   size       while result getLastEvaluatedKey      null    System out println  Result size      totalItemCount

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Similar to Java in PHP only set Select PARAMETER with value  COUNT    result    aws- gt query array    TableName    gt   game table     IndexName    gt   week-point-index     KeyConditions    gt  array       week    gt  array           ComparisonOperator    gt   EQ            AttributeValueList    gt  array              array Type  STRING   gt   week                        point    gt  array           ComparisonOperator    gt   GE            AttributeValueList    gt  array              array Type  NUMBER   gt   my point                        Select    gt   COUNT        and acces it just like this    echo  result  Count     but as Saumitra mentioned above be careful with resultsets largers than 1 MB  in that case use LastEvaluatedKey til it returns null to get the last updated count value

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Can be seen from UI as well  Go to overview tab on table  you will see item count  Hope it helps someone

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I m posting this answer for anyone using C  that wants a fully functional  well-tested answer that demonstrates using query instead of scan   In particular  this answer handles more than 1MB size of items to count          public async Task lt int gt  GetAvailableCount string pool type  string pool key                var queryRequest   new QueryRequest                       TableName   PoolsDb TableName              ConsistentRead   true              Select   Select COUNT              KeyConditionExpression    quot pool type plus pool key    type plus key quot               ExpressionAttributeValues   new Dictionary lt string  AttributeValue gt                      quot  type plus key quot   new AttributeValue   S    pool type   pool key                                      var t0   DateTime UtcNow          var result   await Client QueryAsync queryRequest           var count   result Count          var iter   0          while   result LastEvaluatedKey    null  amp  amp  result LastEvaluatedKey Values Count  gt  0                         iter                var lastkey   result LastEvaluatedKey Values ToList   0  S               logger LogDebug   quot GetAvailableCount  pool type - pool key  iteration  iter  instance key  lastkey  quot                queryRequest ExclusiveStartKey   result LastEvaluatedKey              result   await Client QueryAsync queryRequest               count    result Count                     logger LogDebug   quot GetAvailableCount  pool type - pool key  returned  count  after  iter  iterations in   DateTime UtcNow - t0  TotalMilliseconds  ms  quot            return count

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You could use dynamodb mapper query   PaginatedQueryList lt YourModel gt  list   DymamoDBMapper query YourModel class  queryExpression   int count   list size      it calls loadAllResults   that would lazily load next available result until allResultsLoaded   Ref  https   docs amazonaws cn en us amazondynamodb latest developerguide DynamoDBMapper Methods html DynamoDBMapper Methods query

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You can use the Select parameter and use COUNT in the request  It  returns the number of matching items  rather than the matching items themselves   Important  as brought up by Saumitra R  Bhave in a comment   If the size of the Query result set is larger than 1 MB  then ScannedCount and Count will represent only a partial count of the total items  You will need to perform multiple Query operations in order to retrieve all of the results     I m Not familiar with PHP but here is how you could use it with Java  And then instead of using Count  which I am guessing is a function in PHP  on the  Items  you can use the Count value from the response -  result  Count     final String week    whatever   final Integer myPoint   1337  Condition weekCondition   new Condition            withComparisonOperator ComparisonOperator EQ           withAttributeValueList new AttributeValue   withS week    Condition myPointCondition   new Condition            withComparisonOperator ComparisonOperator GE           withAttributeValueList new AttributeValue   withN myPoint toString      Map lt String  Condition gt  keyConditions   new HashMap lt  gt     keyConditions put  week   weekCondition   keyConditions put  point   myPointCondition    QueryRequest request   new QueryRequest  game table    request setIndexName  week-point-index    request setSelect Select COUNT   request setKeyConditions keyConditions    QueryResult result   dynamoDBClient query request   Integer count   result getCount      If you don t need to emulate the WHERE clause  you can use a DescribeTable request and use the resulting item count to get an estimate      The number of items in the specified table  DynamoDB updates this value approximately every six hours  Recent changes might not be reflected in this value    Also  an important note from the documentation as noted by Saumitra R  Bhave in the comments on this answer      If the size of the Query result set is larger than 1 MB  ScannedCount and Count represent only a partial count of the total items  You need to perform multiple Query operations to retrieve all the results  see Paginating Table Query Results

[database] How to get item count from DynamoDB?

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