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authorJames Ahlborn <jtahlborn@yahoo.com>2014-05-01 03:18:37 +0000
committerJames Ahlborn <jtahlborn@yahoo.com>2014-05-01 03:18:37 +0000
commite24827b6e8e5f500501245e65349823445d20ddb (patch)
tree3dffddefc134a4e7067331f5556a33bbbf56b40e /src/site/xdoc
parent6058071abded03b6b33615d619c50c527245795d (diff)
downloadjackcess-e24827b6e8e5f500501245e65349823445d20ddb.tar.gz
jackcess-e24827b6e8e5f500501245e65349823445d20ddb.zip
add some more cookbook content
git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@857 f203690c-595d-4dc9-a70b-905162fa7fd2
Diffstat (limited to 'src/site/xdoc')
-rw-r--r--src/site/xdoc/cookbook.xml79
1 files changed, 79 insertions, 0 deletions
diff --git a/src/site/xdoc/cookbook.xml b/src/site/xdoc/cookbook.xml
index 8752425..6f13d27 100644
--- a/src/site/xdoc/cookbook.xml
+++ b/src/site/xdoc/cookbook.xml
@@ -283,6 +283,85 @@
speed and memory, they are "lightweight" enough to be used in an
on-demand capacity.
</p>
+ <p>
+ The simplest case involves a normal, un-indexed cursor for a given
+ table. The cursor will traverse the table in no particular row order
+ but it can still be used to find rows where column(s) match
+ specified values. For example...
+ </p>
+<source>
+ Table table = db.getTable("Test");
+ Cursor cursor = CursorBuilder.createCursor(table);
+ boolean found = cursor.findFirstRow(Collections.singletonMap("ID", 1));
+ if (found) {
+ System.out.println(String.format("Row found: Name = '%s'.",
+ cursor.getCurrentRowValue(table.getColumn("Name"))));
+ } else {
+ System.out.println("No matching row was found.");
+ }
+</source>
+ <p>
+ ...will search for the row where <code>"ID" == 1</code>. Since the
+ cursor does not use an index it will perform the equivalent of a
+ "table scan" while searching.
+ </p>
+ <p>
+ Cursors can also use an existing index on the table to (1) control
+ the order in which they traverse the table, and (2) find rows
+ faster. Since we defined the "ID" column as our Primary Key we can
+ also perform the above search like this...
+ </p>
+<source>
+ Table table = db.getTable("Test");
+ IndexCursor cursor = CursorBuilder.createCursor(table.getPrimaryKeyIndex());
+ boolean found = cursor.findFirstRow(Collections.singletonMap("ID", 1));
+ // ... proceed as in previous example ...
+</source>
+ <p>
+ ...or by using the <code>CursorBuilder.findRowByPrimaryKey</code>
+ "convenience method" like this:
+ </p>
+<source>
+ Table table = db.getTable("Test");
+ Row row = CursorBuilder.findRowByPrimaryKey(table, 1);
+ if (row != null) {
+ System.out.println(String.format("Row found: Name = '%s'.",
+ row.get("Name")));
+ } else {
+ System.out.println("No matching row was found.");
+ }
+</source>
+ <p>
+ Either of the two previous approaches will use the Primary Key index
+ to locate the row where <code>"ID" == 1</code>, potentially making
+ it much faster to execute.
+ </p>
+ <p>
+ As mentioned above, an index-backed cursor will also retrieve rows
+ in index order, so if we wanted to retrieve all of the rows in
+ alphabetical order by <code>"Name"</code> we could use the
+ "NameIndex" index to create a cursor and then iterate through the
+ rows like this:
+ </p>
+<source>
+ Table table = db.getTable("Test");
+ IndexCursor cursor = CursorBuilder.createCursor(table.getIndex("NameIndex"));
+ for(Row row : cursor) {
+ System.out.println(String.format("ID=%d, Name='%s'.",
+ row.get("ID"), row.get("Name")));
+ }
+</source>
+ <p>
+ Or, if you wanted to iterate through all of the rows where
+ <code>"Name" == 'bob'</code> you could do:
+ </p>
+<source>
+ Table table = db.getTable("Test");
+ IndexCursor cursor = CursorBuilder.createCursor(table.getIndex("NameIndex"));
+ for(Row row : cursor.newEntryIterable("bob")) {
+ System.out.println(String.format("ID=%d, Name='%s'.", row.get("ID"), row.get("Name")));
+ }
+</source>
</subsection>
<p>