Using multiGet()

TableAPI.multiGet() allows you to retrieve multiple rows at once, so long as they all share the same shard keys. You must specify a full set of shard keys to this method.

Use TableAPI.multiGet() only if your retrieval set will fit entirely in memory.

For example, suppose you have a table that stores information about products, which is designed like this:

CREATE TABLE myTable (
    itemType STRING,
    itemCategory STRING,
    itemClass STRING,
    itemColor STRING,
    itemSize STRING,
    price FLOAT,
    inventoryCount INTEGER,
    PRIMARY KEY (SHARD(itemType, itemCategory, itemClass), itemColor,
    itemSize)
) 

With tables containing data like this:

• Row 1:

  • itemType: Hats

  • itemCategory: baseball

  • itemClass: longbill

  • itemColor: red

  • itemSize: small

  • price: 12.07

  • inventoryCount: 127

• Row 2:

  • itemType: Hats

  • itemCategory: baseball

  • itemClass: longbill

  • itemColor: red

  • itemSize: medium

  • price: 13.07

  • inventoryCount: 201

• Row 3:

  • itemType: Hats

  • itemCategory: baseball

  • itemClass: longbill

  • itemColor: red

  • itemSize: large

  • price: 14.07

  • inventoryCount: 39

In this case, you can retrieve all of the rows with their itemType field set to Hats and their itemCategory field set to baseball. Notice that this represents a partial primary key, because itemClass, itemColor and itemSize are not used for this query.

package kvstore.basicExample;

...

import java.util.List;
import java.util.Iterator;
import oracle.kv.ConsistencyException;
import oracle.kv.KVStore;
import oracle.kv.RequestTimeoutException;
import oracle.kv.table.PrimaryKey;
import oracle.kv.table.Row;
import oracle.kv.table.Table;
import oracle.kv.table.TableAPI;

...

// KVStore handle creation is omitted for brevity

...

TableAPI tableH = kvstore.getTableAPI();

// The name you give to getTable() must be identical
// to the name that you gave the table when you created
// the table using the CREATE TABLE DDL statement.
Table myTable = tableH.getTable("myTable");

// Construct the PrimaryKey. In this case, we are
// using a partial primary key.
PrimaryKey key = myTable.createPrimaryKey();
key.put("itemType", "Hats");
key.put("itemCategory", "baseball");
key.put("itemClass", "longbill");

List<Row> myRows = null;

try {
    myRows = tableH.multiGet(key, null, null);
} catch (ConsistencyException ce) {
    // The consistency guarantee was not met
} catch (RequestTimeoutException re) {
    // The operation was not completed within the
    // timeout value
} 

You can then iterate over the resulting list as follows:

for (Row theRow: myRows) {
    String itemType = theRow.get("itemType").asString().get();
    String itemCategory = theRow.get("itemCategory").asString().get();
    String itemClass = theRow.get("itemClass").asString().get();
    String itemColor = theRow.get("itemColor").asString().get();
    String itemSize = theRow.get("itemSize").asString().get();
    Float price = theRow.get("price").asFloat().get();
    Integer price = theRow.get("itemCount").asInteger().get();
}