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HBASE-13799 javadoc how Scan gets polluted when used; if you set attributes or ask for scan metrics

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stack 2015-05-29 11:31:33 -07:00
parent d86f2fa3b2
commit 62b5e578a8
1 changed files with 13 additions and 20 deletions
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33
hbase-client/src/main/java/org/apache/hadoop/hbase/client/Scan.java
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@ -51,40 +51,33 @@ import org.apache.hadoop.hbase.util.Bytes;
* and stopRow may be defined. If rows are not specified, the Scanner will * and stopRow may be defined. If rows are not specified, the Scanner will
* iterate over all rows. * iterate over all rows.
* <p> * <p>
* To scan everything for each row, instantiate a Scan object. * To get all columns from all rows of a Table, create an instance with no constraints; use the
* {@link #Scan()} constructor. To constrain the scan to specific column families,
* call {@link #addFamily(byte[]) addFamily} for each family to retrieve on your Scan instance.
* <p> * <p>
* To modify scanner caching for just this scan, use {@link #setCaching(int) setCaching}. * To get specific columns, call {@link #addColumn(byte[], byte[]) addColumn}
* If caching is NOT set, we will use the caching value of the hosting {@link Table}.
* In addition to row caching, it is possible to specify a
* maximum result size, using {@link #setMaxResultSize(long)}. When both are used,
* single server requests are limited by either number of rows or maximum result size, whichever
* limit comes first.
* <p>
* To further define the scope of what to get when scanning, perform additional
* methods as outlined below.
* <p>
* To get all columns from specific families, execute {@link #addFamily(byte[]) addFamily}
* for each family to retrieve.
* <p>
* To get specific columns, execute {@link #addColumn(byte[], byte[]) addColumn}
* for each column to retrieve. * for each column to retrieve.
* <p> * <p>
* To only retrieve columns within a specific range of version timestamps, * To only retrieve columns within a specific range of version timestamps,
* execute {@link #setTimeRange(long, long) setTimeRange}. * call {@link #setTimeRange(long, long) setTimeRange}.
* <p> * <p>
* To only retrieve columns with a specific timestamp, execute * To only retrieve columns with a specific timestamp, call
* {@link #setTimeStamp(long) setTimestamp}. * {@link #setTimeStamp(long) setTimestamp}.
* <p> * <p>
* To limit the number of versions of each column to be returned, execute * To limit the number of versions of each column to be returned, call
* {@link #setMaxVersions(int) setMaxVersions}. * {@link #setMaxVersions(int) setMaxVersions}.
* <p> * <p>
* To limit the maximum number of values returned for each call to next(), * To limit the maximum number of values returned for each call to next(),
* execute {@link #setBatch(int) setBatch}. * call {@link #setBatch(int) setBatch}.
* <p> * <p>
* To add a filter, execute {@link #setFilter(org.apache.hadoop.hbase.filter.Filter) setFilter}. * To add a filter, call {@link #setFilter(org.apache.hadoop.hbase.filter.Filter) setFilter}.
* <p> * <p>
* Expert: To explicitly disable server-side block caching for this scan, * Expert: To explicitly disable server-side block caching for this scan,
* execute {@link #setCacheBlocks(boolean)}. * execute {@link #setCacheBlocks(boolean)}.
* <p><em>Note:</em> Usage alters Scan instances. Internally, attributes are updated as the Scan
* runs and if enabled, metrics accumulate in the Scan instance. Be aware this is the case when
* you go to clone a Scan instance or if you go to reuse a created Scan instance; safer is create
* a Scan instance per usage.
*/ */
@InterfaceAudience.Public @InterfaceAudience.Public
@InterfaceStability.Stable @InterfaceStability.Stable