#73 items counting implemented

src/main/java/com/jcabi/dynamo/AwsFrame.java

@@ -30,7 +30,6 @@
 package com.jcabi.dynamo;
 
 import com.amazonaws.services.dynamodbv2.model.Condition;
-import com.google.common.collect.Iterators;
 import com.jcabi.aspects.Immutable;
 import com.jcabi.aspects.Loggable;
 import java.io.IOException;
@@ -130,7 +129,16 @@ public Iterator<Item> iterator() {
 
     @Override
     public int size() {
-        return Iterators.size(this.iterator());
+        try {
+            return this.valve.count(
+                this.credentials, this.name, this.conditions
+            );
+        } catch (final IOException ex) {
+            throw new IllegalStateException(
+                String.format("can't count items in \"%s\"", this.name),
+                ex
+            );
+        }
     }
 
     @Override

src/main/java/com/jcabi/dynamo/QueryValve.java

@@ -177,6 +177,38 @@ public Dosage fetch(final Credentials credentials, final String table,
         }
     }
 
+    @Override
+    public int count(final Credentials credentials, final String table,
+        final Map<String, Condition> conditions) throws IOException {
+        final AmazonDynamoDB aws = credentials.aws();
+        try {
+            QueryRequest request = new QueryRequest()
+                .withTableName(table)
+                .withReturnConsumedCapacity(ReturnConsumedCapacity.TOTAL)
+                .withKeyConditions(conditions)
+                .withConsistentRead(true)
+                .withSelect(Select.COUNT)
+                .withLimit(Integer.MAX_VALUE);
+            if (!this.index.isEmpty()) {
+                request = request.withIndexName(this.index);
+            }
+            final long start = System.currentTimeMillis();
+            final QueryResult rslt = aws.query(request);
+            final int count = rslt.getCount();
+            Logger.info(
+                this,
+                // @checkstyle LineLength (1 line)
+                "#total(): COUNT=%d in '%s' using %s, %s, in %[ms]s",
+                count, request.getTableName(), request.getQueryFilter(),
+                AwsTable.print(rslt.getConsumedCapacity()),
+                System.currentTimeMillis() - start
+            );
+            return count;
+        } finally {
+            aws.shutdown();
+        }
+    }
+
     /**
      * With consistent read.
      * @param cnst Consistent read

src/main/java/com/jcabi/dynamo/ScanValve.java

@@ -62,7 +62,7 @@
 @Immutable
 @ToString
 @Loggable(Loggable.DEBUG)
-@EqualsAndHashCode(of = { "limit" })
+@EqualsAndHashCode(of = { "limit", "attributes" })
 public final class ScanValve implements Valve {
 
     /**
@@ -133,6 +133,23 @@ public Dosage fetch(final Credentials credentials,
         }
     }
 
+    @Override
+    public int count(final Credentials credentials, final String table,
+        final Map<String, Condition> conditions) throws IOException {
+        Dosage dosage = this.fetch(
+            credentials, table, conditions, Collections.<String>emptyList()
+        );
+        int count = 0;
+        while (true) {
+            count += dosage.items().size();
+            if (!dosage.hasNext()) {
+                break;
+            }
+            dosage = dosage.next();
+        }
+        return count;
+    }
+
     /**
      * With given limit.
      * @param lmt Limit to use

src/main/java/com/jcabi/dynamo/Valve.java

@@ -59,4 +59,15 @@ Dosage fetch(Credentials credentials, String table,
         Map<String, Condition> conditions, Collection<String> keys)
         throws IOException;
 
+    /**
+     * Count items.
+     * @param credentials Credentials to AWS
+     * @param table Table name
+     * @param conditions Conditions
+     * @return Total count of the
+     * @throws IOException In case of DynamoDB failure
+     */
+    int count(Credentials credentials, String table,
+        Map<String, Condition> conditions) throws IOException;
+
 }

src/main/java/com/jcabi/dynamo/retry/ReValve.java

@@ -81,4 +81,11 @@ public Dosage fetch(final Credentials credentials, final String table,
         );
     }
 
+    @Override
+    @RetryOnFailure(verbose = false, delay = Tv.FIVE, unit = TimeUnit.SECONDS)
+    public int count(final Credentials credentials, final String table,
+        final Map<String, Condition> conditions) throws IOException {
+        return this.origin.count(credentials, table, conditions);
+    }
+
 }

src/test/java/com/jcabi/dynamo/AwsFrameITCase.java

@@ -52,12 +52,35 @@ public void calculatesItems() throws Exception {
         final String name = RandomStringUtils.randomAlphabetic(Tv.EIGHT);
         final RegionMock mock = new RegionMock();
         final Table tbl = mock.get(name).table(name);
-        final Attributes attrs = new Attributes().with(mock.range(), 1L);
+        final String hash = "hello";
+        final Attributes attrs = new Attributes().with(mock.hash(), hash);
         for (int idx = 0; idx < Tv.TEN; ++idx) {
-            tbl.put(attrs.with(mock.hash(), String.format("i%d", idx)));
+            tbl.put(attrs.with(mock.range(), idx));
         }
         MatcherAssert.assertThat(
-            tbl.frame().through(new ScanValve().withLimit(1)).size(),
+            tbl.frame()
+                .through(new ScanValve().withLimit(1))
+                .size(),
+            Matchers.equalTo(Tv.TEN)
+        );
+        MatcherAssert.assertThat(
+            tbl.frame()
+                .through(new ScanValve().withLimit(Tv.HUNDRED))
+                .size(),
+            Matchers.equalTo(Tv.TEN)
+        );
+        MatcherAssert.assertThat(
+            tbl.frame()
+                .through(new QueryValve().withLimit(1))
+                .where(mock.hash(), hash)
+                .size(),
+            Matchers.equalTo(Tv.TEN)
+        );
+        MatcherAssert.assertThat(
+            tbl.frame()
+                .through(new QueryValve().withLimit(Tv.HUNDRED))
+                .where(mock.hash(), hash)
+                .size(),
             Matchers.equalTo(Tv.TEN)
         );
     }