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Posted to dev@accumulo.apache.org by dhutchis <gi...@git.apache.org> on 2015/08/24 04:22:33 UTC
[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
GitHub user dhutchis opened a pull request:
https://github.com/apache/accumulo/pull/45
ACCUMULO-3959 More accurate BatchScanner javadoc
This will help clear possible confusion on when to use BatchScanners vs Scanners.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dhutchis/accumulo ACCUMULO-3959
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/accumulo/pull/45.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #45
----
commit 01dd7e32e864c7359f8b289f1434c9d9a5c154d4
Author: Dylan Hutchison <dh...@mit.edu>
Date: 2015-08-24T02:19:47Z
ACCUMULO-3959 More accurate BatchScanner javadoc
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[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
Posted by keith-turner <gi...@git.apache.org>.
Github user keith-turner commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/45#discussion_r37789259
--- Diff: core/src/main/java/org/apache/accumulo/core/client/BatchScanner.java ---
@@ -16,19 +16,20 @@
*/
package org.apache.accumulo.core.client;
+import org.apache.accumulo.core.data.Range;
+
import java.util.Collection;
import java.util.concurrent.TimeUnit;
-import org.apache.accumulo.core.data.Range;
-
/**
* Implementations of BatchScanner support efficient lookups of many ranges in accumulo.
+ * BatchScanners are also appropriate for large, single ranges,
+ * as a BatchScanner will break those ranges up into separate RPCs
+ * provided the range spans more than one tablet
+ * and there are sufficiently many scan threads available.
--- End diff --
Maybe instead of suggesting how to use the batch scanner, we could focus more on describing possible behavior?
* May parallelize reading of data. Multiple input ranges may be read in parallel or sub ranges of individual input ranges may be read in parallel.
* May return data in unsorted order.
* May batch multiple ranges into a single RPC to a tserver.
Could still mention possible use cases like :
* Looking up lots of small ranges
* Parallelizing (spell check in web browser does not like that word) a computation over an entire table using a large range w/ iterators. This case may not return lots of data, although lots of data may be read by the iterators.
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[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
Posted by keith-turner <gi...@git.apache.org>.
Github user keith-turner commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/45#discussion_r37784571
--- Diff: core/src/main/java/org/apache/accumulo/core/client/BatchScanner.java ---
@@ -16,19 +16,20 @@
*/
package org.apache.accumulo.core.client;
+import org.apache.accumulo.core.data.Range;
+
import java.util.Collection;
import java.util.concurrent.TimeUnit;
-import org.apache.accumulo.core.data.Range;
-
/**
* Implementations of BatchScanner support efficient lookups of many ranges in accumulo.
+ * BatchScanners are also appropriate for large, single ranges,
+ * as a BatchScanner will break those ranges up into separate RPCs
+ * provided the range spans more than one tablet
+ * and there are sufficiently many scan threads available.
*
- * Use this when looking up lots of ranges and you expect each range to contain a small amount of data. Also only use this when you do not care about the
- * returned data being in sorted order.
- *
- * If you want to lookup a few ranges and expect those ranges to contain a lot of data, then use the Scanner instead. Also, the Scanner will return data in
- * sorted order, this will not.
+ * Only use this when you do not care about returned data being in sorted order.
--- End diff --
This was already broken before your patch, but I think javadoc need `<p>` markup for paragraphs. Not sure it will render as intended w/o it.
Did you format these changes?
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[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
Posted by asfgit <gi...@git.apache.org>.
Github user asfgit closed the pull request at:
https://github.com/apache/accumulo/pull/45
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[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
Posted by joshelser <gi...@git.apache.org>.
Github user joshelser commented on the pull request:
https://github.com/apache/accumulo/pull/45#issuecomment-134319018
+1 from me. Will merge today.
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[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
Posted by dhutchis <gi...@git.apache.org>.
Github user dhutchis commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/45#discussion_r37785744
--- Diff: core/src/main/java/org/apache/accumulo/core/client/BatchScanner.java ---
@@ -16,19 +16,20 @@
*/
package org.apache.accumulo.core.client;
+import org.apache.accumulo.core.data.Range;
+
import java.util.Collection;
import java.util.concurrent.TimeUnit;
-import org.apache.accumulo.core.data.Range;
-
/**
* Implementations of BatchScanner support efficient lookups of many ranges in accumulo.
+ * BatchScanners are also appropriate for large, single ranges,
+ * as a BatchScanner will break those ranges up into separate RPCs
+ * provided the range spans more than one tablet
+ * and there are sufficiently many scan threads available.
*
- * Use this when looking up lots of ranges and you expect each range to contain a small amount of data. Also only use this when you do not care about the
- * returned data being in sorted order.
- *
- * If you want to lookup a few ranges and expect those ranges to contain a lot of data, then use the Scanner instead. Also, the Scanner will return data in
- * sorted order, this will not.
+ * Only use this when you do not care about returned data being in sorted order.
--- End diff --
Correct, I see that the <p> tag is necessary from the online javadoc at
http://accumulo.apache.org/1.7/apidocs/org/apache/accumulo/core/client/BatchScanner.html
Will fix tonight when I return to my laptop. I don't think my editor
(IntelliJ with the Eclipse code formatter plugin) adds the HTML tags
automatically.
On Mon, Aug 24, 2015 at 2:25 PM, Keith Turner <no...@github.com>
wrote:
> In core/src/main/java/org/apache/accumulo/core/client/BatchScanner.java
> <https://github.com/apache/accumulo/pull/45#discussion_r37784571>:
>
> > *
> > - * Use this when looking up lots of ranges and you expect each range to contain a small amount of data. Also only use this when you do not care about the
> > - * returned data being in sorted order.
> > - *
> > - * If you want to lookup a few ranges and expect those ranges to contain a lot of data, then use the Scanner instead. Also, the Scanner will return data in
> > - * sorted order, this will not.
> > + * Only use this when you do not care about returned data being in sorted order.
>
> This was already broken before your patch, but I think javadoc need <p>
> markup for paragraphs. Not sure it will render as intended w/o it.
>
> Did you format these changes?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/apache/accumulo/pull/45/files#r37784571>.
>
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[GitHub] accumulo pull request: ACCUMULO-3959 More accurate BatchScanner ja...
Posted by keith-turner <gi...@git.apache.org>.
Github user keith-turner commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/45#discussion_r37789345
--- Diff: core/src/main/java/org/apache/accumulo/core/client/BatchScanner.java ---
@@ -16,19 +16,20 @@
*/
package org.apache.accumulo.core.client;
+import org.apache.accumulo.core.data.Range;
+
import java.util.Collection;
import java.util.concurrent.TimeUnit;
-import org.apache.accumulo.core.data.Range;
-
/**
* Implementations of BatchScanner support efficient lookups of many ranges in accumulo.
+ * BatchScanners are also appropriate for large, single ranges,
+ * as a BatchScanner will break those ranges up into separate RPCs
+ * provided the range spans more than one tablet
+ * and there are sufficiently many scan threads available.
*
- * Use this when looking up lots of ranges and you expect each range to contain a small amount of data. Also only use this when you do not care about the
- * returned data being in sorted order.
- *
- * If you want to lookup a few ranges and expect those ranges to contain a lot of data, then use the Scanner instead. Also, the Scanner will return data in
- * sorted order, this will not.
--- End diff --
Not 100% sure, but I think I wrote this javadoc. My thinking was that the Scanner does pipelining and may have better performance for reading data to a single client. However, this may be completely wrong. I think removing this suggestions is a good idea.
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