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new 83211c2 Refactor listSplits operation when using maxSplits (#2381)
83211c2 is described below
commit 83211c207cc74c30e25433b595026d31752ba2be
Author: Mark Owens <jmar...@apache.org>
AuthorDate: Mon Dec 13 09:17:35 2021 -0500
Refactor listSplits operation when using maxSplits (#2381)
Refactored listSplits method in TableOperationsImpl. This change affects
the listSplits command which takes maxSplits as an option.
* Renamed variable names to enhance readability.
* Added documentation for the method.
* Replaced while-loop with if-loop after determining while-loop was only
run at most once each time.
* Created IT test for method in ShellIT class.
Closes #2371
Co-authored-by: Keith Turner <ktur...@apache.org>
---
.../core/clientImpl/TableOperationsImpl.java | 66 ++++++++++++++++------
.../java/org/apache/accumulo/test/ShellIT.java | 23 ++++++++
2 files changed, 71 insertions(+), 18 deletions(-)
diff --git
a/core/src/main/java/org/apache/accumulo/core/clientImpl/TableOperationsImpl.java
b/core/src/main/java/org/apache/accumulo/core/clientImpl/TableOperationsImpl.java
index c95910f..202860a 100644
---
a/core/src/main/java/org/apache/accumulo/core/clientImpl/TableOperationsImpl.java
+++
b/core/src/main/java/org/apache/accumulo/core/clientImpl/TableOperationsImpl.java
@@ -689,28 +689,59 @@ public class TableOperationsImpl extends
TableOperationsHelper {
}
+ /**
+ * This version of listSplits is called when the maxSplits options is
provided. If the value of
+ * maxSplits is greater than the number of existing splits, then all splits
are returned and no
+ * additional processing is performed.
+ *
+ * But, if the value of maxSplits is less than the number of existing
splits, maxSplit split
+ * values are returned. These split values are "evenly" selected from the
existing splits based
+ * upon the algorithm implemented in the method.
+ *
+ * A stepSize is calculated based upon the number of splits requested and
the total split count. A
+ * running sum adjusted by this stepSize is calculated as each split is
parsed. Once this sum
+ * exceeds a value of 1, the current split point is selected to be returned.
The sum is then
+ * decremented by 1 and the process continues until all existing splits have
been parsed or
+ * maxSplits splits have been selected.
+ *
+ * @param tableName
+ * the name of the table
+ * @param maxSplits
+ * specifies the maximum number of splits to return
+ * @return a Collection containing a subset of evenly selected splits
+ */
@Override
- public Collection<Text> listSplits(String tableName, int maxSplits)
+ public Collection<Text> listSplits(final String tableName, final int
maxSplits)
throws TableNotFoundException, AccumuloSecurityException {
// tableName is validated in _listSplits
- List<Text> endRows = _listSplits(tableName);
- if (endRows.size() <= maxSplits)
- return endRows;
-
- double r = (maxSplits + 1) / (double) (endRows.size());
- double pos = 0;
- ArrayList<Text> subset = new ArrayList<>(maxSplits);
- int j = 0;
- for (int i = 0; i < endRows.size() && j < maxSplits; i++) {
- pos += r;
- while (pos > 1) {
- subset.add(endRows.get(i));
- j++;
- pos -= 1;
- }
+ final List<Text> existingSplits = _listSplits(tableName);
+
+ // As long as maxSplits is equal to or larger than the number of current
splits, the existing
+ // splits are returned and no additional processing is necessary.
+ if (existingSplits.size() <= maxSplits) {
+ return existingSplits;
}
- return subset;
+ // When the number of maxSplits requested is less than the number of
existing splits, the
+ // following code populates the splitsSubset list 'evenly' from the
existing splits
+ ArrayList<Text> splitsSubset = new ArrayList<>(maxSplits);
+ final int SELECTION_THRESHOLD = 1;
+
+ // stepSize can never be greater than 1 due to the if-loop check above.
+ final double stepSize = (maxSplits + 1) / (double) (existingSplits.size());
+ double selectionTrigger = 0.0;
+
+ for (Text existingSplit : existingSplits) {
+ if (splitsSubset.size() >= maxSplits) {
+ break;
+ }
+ selectionTrigger += stepSize;
+ if (selectionTrigger > SELECTION_THRESHOLD) {
+ splitsSubset.add(existingSplit);
+ selectionTrigger -= 1;
+ }
+ }
+ return splitsSubset;
}
@Override
@@ -727,7 +758,6 @@ public class TableOperationsImpl extends
TableOperationsHelper {
// should not happen
throw new AssertionError(e);
}
-
}
@Override
diff --git a/test/src/main/java/org/apache/accumulo/test/ShellIT.java
b/test/src/main/java/org/apache/accumulo/test/ShellIT.java
index 0136f6c..86c9cb7 100644
--- a/test/src/main/java/org/apache/accumulo/test/ShellIT.java
+++ b/test/src/main/java/org/apache/accumulo/test/ShellIT.java
@@ -589,4 +589,27 @@ public class ShellIT extends SharedMiniClusterBase {
}
}
+ // Test the maxSplits option for getsplits/listsplits.
+ @Test
+ public void testMaxSplitsOption() throws Exception {
+ Shell.log.debug("Starting testMaxSplits test ------------------");
+ exec("createtable maxtab", true);
+ exec("addsplits 0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s
t", true);
+ exec("getsplits -m 31", true,
+
"0\n1\n2\n3\n4\n5\n6\n7\n8\n9\na\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\nn\no\np\nq\nr\ns\nt\n");
+ exec("getsplits -m 30", true,
+
"0\n1\n2\n3\n4\n5\n6\n7\n8\n9\na\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\nn\no\np\nq\nr\ns\nt\n");
+ exec("getsplits -m 29", true,
+
"1\n2\n3\n4\n5\n6\n7\n8\n9\na\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\nn\no\np\nq\nr\ns\nt\n");
+ exec("getsplits -m 15", true,
"1\n3\n5\n7\n9\nb\nd\nf\ng\ni\nk\nm\no\nq\ns\n");
+ exec("getsplits -m 10", true, "2\n5\n8\na\nd\ng\nj\nl\no\nr\n");
+ exec("getsplits -m 5", true, "5\na\nf\nk\np\n");
+ exec("getsplits -m 3", true, "7\nf\nm\n");
+ exec("getsplits -m 1", true, "f\n");
+ // if 0 is supplied as maxSplits, the non-maxSplits version of getsplits
is called and all
+ // are returned.
+ exec("getsplits -m 0", true,
+
"0\n1\n2\n3\n4\n5\n6\n7\n8\n9\na\nb\nc\nd\ne\nf\ng\nh\ni\nj\nk\nl\nm\nn\no\np\nq\nr\ns\nt\n");
+ }
+
}
