<!DOCTYPE html>
<html>
<head>
</head>
<body>
<dl style="line-height: 1.5; margin-left: 2em">
<dt style="clear: both; float: left; font-weight: bold; width: 8em">Author</dt>
<dd style="margin-left: 8.5em">Kouhei Sutou <kou****@clear*****></dd>
<dt style="clear: both; float: left; font-weight: bold; width: 8em">Date</dt>
<dd style="margin-left: 8.5em">2011-06-21 11:35:16 +0900 (Tue, 21 Jun 2011)</dd>
<dt style="clear: both; float: left; font-weight: bold; width: 8em">New Revision</dt>
<dd style="margin-left: 8.5em"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36">b3c3f8068a930b762cfc0b6f6a2040c66b62fd36</a></dd>
<dt style="clear: both; float: left; font-weight: bold; width: 8em">Log</dt>
<dd style="margin-left: 8.5em"><pre style="border: 1px solid #aaa; font-family: Consolas, Menlo, "Liberation Mono", Courier, monospace; line-height: 1.2; padding: 0.5em">[doc] add missing escape.</pre></dd>
<dt style="clear: both; float: left; font-weight: bold; width: 8em">Modified files</dt>
<dd style="margin-left: 8.5em">
<ul>
<li><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#diff-0">doc/ja/source/userguide.rst</a></li>
</ul>
</dd>
</dl>
<div class="diff-section" style="clear: both">
<table style="border-collapse: collapse; border: 1px solid #aaa">
<thead>
<tr class="diff-header" style="border: 1px solid #aaa">
<td colspan="3">
<pre style="border: 0; font-family: Consolas, Menlo, "Liberation Mono", Courier, monospace; line-height: 1.2; margin: 0; padding: 0.5em; white-space: normal"><span class="diff-header" style="background-color: #eaf2f5; color: #999999; display: block; white-space: pre"> Modified: doc/ja/source/userguide.rst (+1 -1)</span>
<span class="diff-header-mark" style="background-color: #eaf2f5; color: #999999; display: block; white-space: pre">===================================================================</span>
</pre>
</td>
</tr>
</thead>
<tbody>
<tr>
<th class="diff-line-number" style="border: 1px solid #aaa">
<pre style="border: 0; font-family: Consolas, Menlo, "Liberation Mono", Courier, monospace; line-height: 1.2; margin: 0; padding: 0.5em; white-space: normal"><span class="diff-line-number-hunk-header" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L258">...</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L259">259</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L260">260</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L261">261</a></span>
<span class="diff-line-number-deleted" style="background-color: #ffaaaa; color: #000000; display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L262">262</a></span>
<span class="diff-line-number-nothing" style="display: block; white-space: pre"> </span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L263">263</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L264">264</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0L265">265</a></span>
</pre>
</th>
<th class="diff-line-number" style="border: 1px solid #aaa">
<pre style="border: 0; font-family: Consolas, Menlo, "Liberation Mono", Courier, monospace; line-height: 1.2; margin: 0; padding: 0.5em; white-space: normal"><span class="diff-line-number-hunk-header" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R258">...</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R259">259</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R260">260</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R261">261</a></span>
<span class="diff-line-number-nothing" style="display: block; white-space: pre"> </span>
<span class="diff-line-number-added" style="background-color: #aaffaa; color: #000000; display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R262">262</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R263">263</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R264">264</a></span>
<span class="diff-line-number-not-changed" style="display: block; white-space: pre"><a href="https://github.com/mroonga/mroonga/commit/b3c3f8068a930b762cfc0b6f6a2040c66b62fd36#L0R265">265</a></span>
</pre>
</th>
<td class="diff-content" style="border: 1px solid #aaa">
<pre style="border: 0; font-family: Consolas, Menlo, "Liberation Mono", Courier, monospace; line-height: 1.2; margin: 0; padding: 0.5em; white-space: normal"><span class="diff-hunk-header" style="background-color: #eaf2f5; color: #999999; display: block; white-space: pre">@@ -259,7 +259,7 @@ <span class="diff-context" style="background-color: #ffffaa; color: #000000">groongaでは各カラムごとにファイルを分けてデータを格納す</span></span>
<span class="diff-not-changed" style="display: block; white-space: pre"> 行カウント高速化</span>
<span class="diff-not-changed" style="display: block; white-space: pre"> ----------------</span>
<span class="diff-not-changed" style="display: block; white-space: pre"> </span>
<span class="diff-deleted" style="background-color: #ffaaaa; color: #000000; display: block; white-space: pre">-COUNT(*)などの行カウントを行う場合と通常のSELECTによるデータ参照を行う場合に対して、従来よりMySQLではストレージエンジンの呼び出しを行う部分(=ストレージエンジンインタフェース)における区別が存在していないため、行数をカウントするだけで良いような場合にもレコードアクセス（SELECTの結果には含まれないデータへのアクセス）が行われる問題があります。</span>
<span class="diff-added" style="background-color: #aaffaa; color: #000000; display: block; white-space: pre">+COUNT(\*)などの行カウントを行う場合と通常のSELECTによるデータ参照を行う場合に対して、従来よりMySQLではストレージエンジンの呼び出しを行う部分(=ストレージエンジンインタフェース)における区別が存在していないため、行数をカウントするだけで良いような場合にもレコードアクセス（SELECTの結果には含まれないデータへのアクセス）が行われる問題があります。</span>
<span class="diff-not-changed" style="display: block; white-space: pre"> </span>
<span class="diff-not-changed" style="display: block; white-space: pre"> groongaストレージエンジンの前身であるTritonn(MySQL+Senna)ではこの問題に対して"2indパッチ"という不要なレコードアクセスを省略する仕組みを独自に実装してこの性能問題を回避していました。</span>
<span class="diff-not-changed" style="display: block; white-space: pre"> </span>
</pre>
</td>
</tr>
</tbody>
</table>
</div>
</body>
</html>