Multiple bookmarks #376
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Multiple bookmarks #376
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lutovich
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zhenlineo
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May 23, 2017
| while ( iterator.hasNext() ) | ||
| { | ||
| String bookmark = iterator.next(); | ||
| long value = bookmarkValue( bookmark ); |
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value might be null for the following case:
bookmarks = new String[]{aBookmark, null, null};
zhenlineo
reviewed
May 23, 2017
| } | ||
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| @Override | ||
| public Session session( Collection<String> bookmarks ) |
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Five methods can be merged in to two
public Session session( String... bookmark )
public Session session( AccessMode mode, String... bookmark )
zhenlineo
reviewed
May 24, 2017
| return maxValue; | ||
| } | ||
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| public Map<String,Value> asParameters() |
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maybe asBeginTransactionParameters()?
Previously it was possible to only supply a single bookmark when creating
a new session. However there is a use-case to be able to supply multiple
bookmarks when multiple worker threads execute write queries and then
reader should be able to observe all those writes. To achieve this driver
now exposed session creation methods that take an iterable of bookmarks.
It was chosen to add additional `Driver#session()` overloads with
`Iterable<String>` instead of extending single-bookmark methods with
varargs because:
* this maintains backwards compatibility for pre-existing methods
* addition of varargs would make API look strange because call or
`Driver#session()` and call of `Driver#session(String... bookmarks)`
without params is essentially the same thing
* invocation of vararg methods with single `null` argument can be confusing
* varargs are more suitable for manual params listing
Driver will now send:
```
{
bookmark: "max",
bookmarks: ["one", "two", "max"]
}
```
instead of simple:
```
{
bookmark: "max"
}
```
this is done to maintain backwards compatibility with databases that
only support single bookmark. It forces driver to parse and compare
bookmarks which violates the fact that bookmarks are opaque. This is
done only to maintain backwards compatibility and should not be copied.
Code doing this will eventually be removed.
lutovich
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zhenlineo
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| return maxValue == null; | ||
| } | ||
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| public String asString() |
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This method name is confusing in a way that I would question why only return one bookmark rather than all of them back (like toString method).
Maybe change to names like asSingleString(), or maxBookmarkAsString, or singleBookmarkAsString?
zhenlineo
reviewed
May 24, 2017
| } | ||
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| @Test | ||
| public void bookmarkFromIterable() |
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What about a test for
Bookmark bookmark = Bookmark.from( asList(
null, "neo4j:bookmark:v1:tx10", "neo4j:bookmark:v1:tx12" ) );
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* improve method naming in `Bookmark` * handle `null` bookmark in given `Iterable`
|
LGTM |
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Previously it was possible to only supply a single bookmark when creating a new session. However there is a use-case to be able to supply multiple bookmarks when multiple worker threads execute write queries and then reader should be able to observe all those writes. To achieve this driver now exposed session creation methods that take an iterable of bookmarks.
It was chosen to add additional
Driver#session()overloads withIterable<String>instead of extending single-bookmark methods with varargs because:Driver#session()and call ofDriver#session(String... bookmarks)without params is essentially the same thingnullargument can be confusingDriver will now send:
instead of simple:
this is done to maintain backwards compatibility with databases that only support single bookmark. It forces driver to parse and compare bookmarks which violates the fact that bookmarks are opaque. This is done only to maintain backwards compatibility and should not be copied. Code doing this will eventually be removed.
Related Bolt server PR: neo4j/neo4j#9404