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| author | Lorry Tar Creator <lorry-tar-importer@baserock.org> | 2015-02-17 17:25:57 +0000 |
|---|---|---|
| committer | <> | 2015-03-17 16:26:24 +0000 |
| commit | 780b92ada9afcf1d58085a83a0b9e6bc982203d1 (patch) | |
| tree | 598f8b9fa431b228d29897e798de4ac0c1d3d970 /docs/programmer_reference/am_misc_bulk.html | |
| parent | 7a2660ba9cc2dc03a69ddfcfd95369395cc87444 (diff) | |
| download | berkeleydb-master.tar.gz | |
Diffstat (limited to 'docs/programmer_reference/am_misc_bulk.html')
| -rw-r--r-- | docs/programmer_reference/am_misc_bulk.html | 222 |
1 files changed, 141 insertions, 81 deletions
diff --git a/docs/programmer_reference/am_misc_bulk.html b/docs/programmer_reference/am_misc_bulk.html index fcfd4736..f69e712b 100644 --- a/docs/programmer_reference/am_misc_bulk.html +++ b/docs/programmer_reference/am_misc_bulk.html @@ -14,7 +14,7 @@ <body> <div xmlns="" class="navheader"> <div class="libver"> - <p>Library Version 11.2.5.3</p> + <p>Library Version 12.1.6.1</p> </div> <table width="100%" summary="Navigation header"> <tr> @@ -22,9 +22,7 @@ </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="am_misc.html">Prev</a> </td> - <th width="60%" align="center">Chapter 4. - Access Method Wrapup - </th> + <th width="60%" align="center">Chapter 4. Access Method Wrapup </th> <td width="20%" align="right"> <a accesskey="n" href="am_misc_partial.html">Next</a></td> </tr> </table> @@ -57,11 +55,12 @@ </dt> </dl> </div> - <p>When retrieving or modifying large numbers of records, the number -of method calls can often dominate performance. Berkeley DB offers bulk get, -put and delete interfaces which can significantly increase performance for some -applications. -</p> + <p> + When retrieving or modifying large numbers of records, the + number of method calls can often dominate performance. + Berkeley DB offers bulk get, put and delete interfaces which + can significantly increase performance for some applications. + </p> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> <div> @@ -70,68 +69,78 @@ applications. </div> </div> </div> + <p> + To retrieve records in bulk, an application buffer must + be specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> methods. This is + done in the C API by setting the <span class="bold"><strong>data</strong></span> + and <span class="bold"><strong>ulen</strong></span> fields of the + <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> to reference an application + buffer, and the <span class="bold"><strong>flags</strong></span> + field of that structure to <a href="../api_reference/C/dbt.html#dbt_DB_DBT_USERMEM" class="olink">DB_DBT_USERMEM</a>. In the + Berkeley DB C++ and Java APIs, the actions are similar, + although there are API-specific methods to set the <a href="../api_reference/C/dbt.html" class="olink">DBT</a> + values. Then, the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> or <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flags + are specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> methods, which + cause multiple records to be returned in the specified + buffer. + </p> <p> - To retrieve records in bulk, an application buffer must be specified to - the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> methods. This is done in the C API by setting - the <span class="bold"><strong>data</strong></span> and <span class="bold"><strong>ulen</strong></span> fields of the <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> to reference an application - buffer, and the - <span class="bold"><strong>flags</strong></span> field of that structure to - <a href="../api_reference/C/dbt.html#dbt_DB_DBT_USERMEM" class="olink">DB_DBT_USERMEM</a>. In the Berkeley DB C++ and Java APIs, the actions - are similar, although there are API-specific methods to set the <a href="../api_reference/C/dbt.html" class="olink">DBT</a> - values. Then, the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> or <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flags are - specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> methods, which cause multiple - records to be returned in the specified buffer. -</p> + The difference between <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> and + <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> is as follows: <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> returns + multiple data items for a single key. For example, the + <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag would be used to retrieve all of the + duplicate data items for a single key in a single call. + The <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag is used to retrieve multiple + key/data pairs, where each returned key may or may not + have duplicate data items. + </p> + <p> + Once the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> method has returned, the + application will walk through the buffer handling the + returned records. This is implemented for the C and C++ + APIs using four macros: <a href="../api_reference/C/DB_MULTIPLE_INIT.html" class="olink">DB_MULTIPLE_INIT</a>, + <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a>, <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a>, and + <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a>. For the Java API, this is + implemented as three iterator classes: <a class="ulink" href="../java/com/sleepycat/db/MultipleDataEntry.html" target="_top">MultipleDataEntry</a>, + <a class="ulink" href="../java/com/sleepycat/db/MultipleKeyDataEntry.html" target="_top">MultipleKeyDataEntry</a>, + and <a class="ulink" href="../java/com/sleepycat/db/MultipleRecnoDataEntry.html" target="_top"> + MultipleRecnoDataEntry</a>. + </p> <p> - The difference between <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> and <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> is as - follows: <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> returns multiple data items for a single key. - For example, the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag would be used to retrieve all of - the duplicate data items for a single key in a single call. The - <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag is used to retrieve multiple key/data pairs, - where each returned key may or may not have duplicate data items. -</p> + The <a href="../api_reference/C/DB_MULTIPLE_INIT.html" class="olink">DB_MULTIPLE_INIT</a> macro is always called first. It + initializes a local application variable and the <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> for stepping through + the set of returned records. Then, the application calls + one of the remaining three macros: <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a>, + <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a>, and <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a>. + </p> <p> - Once the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> method has returned, the application will - walk through the buffer handling the returned records. This is - implemented for the C and C++ APIs using four macros: - <a href="../api_reference/C/DB_MULTIPLE_INIT.html" class="olink">DB_MULTIPLE_INIT</a>, <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a>, <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a>, and - <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a>. For the Java API, this is implemented as - three iterator classes: - <a class="ulink" href="../java/com/sleepycat/db/MultipleDataEntry.html" target="_top">MultipleDataEntry</a>, - <a class="ulink" href="../java/com/sleepycat/db/MultipleKeyDataEntry.html" target="_top">MultipleKeyDataEntry</a>, - and <a class="ulink" href="../java/com/sleepycat/db/MultipleRecnoDataEntry.html" target="_top">MultipleRecnoDataEntry</a>. -</p> - <p> - The <a href="../api_reference/C/DB_MULTIPLE_INIT.html" class="olink">DB_MULTIPLE_INIT</a> macro is always called first. It initializes a - local application variable and the <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> for stepping through the set of - returned records. Then, the application calls one of the remaining - three macros: <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a>, <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a>, and - <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a>. -</p> - <p> - If the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag was specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> - method, the application will always call the <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a> macro. - If the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag was specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> - method, and the underlying database is a Btree or Hash database, the - application will always call the <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a> macro. If the - <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag was specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> method, - and the underlying database is a Queue or Recno database, the - application will always call the <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a> macro. The - <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a>, <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a>, and - <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a> macros are called repeatedly, until the end of - the returned records is reached. The end of the returned records is - detected by the application's local pointer variable being set to NULL. -</p> - <p> - Note that if you want to use a cursor for bulk retrieval of records in - a Btree database, you should open the cursor using the - <code class="literal">DB_CURSOR_BULK</code> flag. This optimizes the cursor for - bulk retrieval. -</p> - <p> - The following is an example of a routine that displays the contents of - a Btree database using the bulk return interfaces. -</p> + If the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag was specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> + or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> method, the application will always call the + <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a> macro. If the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag + was specified to the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> method, and the + underlying database is a Btree or Hash database, the + application will always call the <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a> + macro. If the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag was specified to the + <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> or <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> method, and the underlying database is + a Queue or Recno database, the application will always + call the <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a> macro. The + <a href="../api_reference/C/DB_MULTIPLE_NEXT.html" class="olink">DB_MULTIPLE_NEXT</a>, <a href="../api_reference/C/DB_MULTIPLE_KEY_NEXT.html" class="olink">DB_MULTIPLE_KEY_NEXT</a>, and + <a href="../api_reference/C/DB_MULTIPLE_RECNO_NEXT.html" class="olink">DB_MULTIPLE_RECNO_NEXT</a> macros are called repeatedly, + until the end of the returned records is reached. The end + of the returned records is detected by the application's + local pointer variable being set to NULL. + </p> + <p> + Note that if you want to use a cursor for bulk + retrieval of records in a Btree database, you should open + the cursor using the <code class="literal">DB_CURSOR_BULK</code> + flag. This optimizes the cursor for bulk retrieval. + </p> + <p> + The following is an example of a routine that displays + the contents of a Btree database using the bulk return + interfaces. + </p> <a id="prog_am22"></a> <pre class="programlisting">int rec_display(DB *dbp) @@ -205,13 +214,34 @@ rec_display(DB *dbp) </div> </div> </div> - <p>To put records in bulk with the btree or hash access methods, construct bulk buffers in the <span class="bold"><strong>key</strong></span> and <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_WRITE_NEXT.html" class="olink">DB_MULTIPLE_WRITE_NEXT</a>. To put records in bulk with the recno or queue access methods, construct bulk buffers in the <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> as before, but construct the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a> with a data size of zero;. In both cases, set the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag to <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a>.</p> - <p>Alternatively, for btree and hash access methods, construct a single bulk buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_KEY_WRITE_NEXT.html" class="olink">DB_MULTIPLE_KEY_WRITE_NEXT</a>. For recno and queue access methods, construct a bulk buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a>. In both cases, set the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag to <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a>. - -</p> - <p>A successful bulk operation is logically equivalent to a loop through each key/data pair, performing a <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a> for each one.</p> <p> -</p> + To put records in bulk with the btree or hash access + methods, construct bulk buffers in the <span class="bold"><strong>key</strong></span> and <span class="bold"><strong>data</strong></span> + <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> + and <a href="../api_reference/C/DB_MULTIPLE_WRITE_NEXT.html" class="olink">DB_MULTIPLE_WRITE_NEXT</a>. To put records in bulk with + the recno or queue access methods, construct bulk buffers + in the <span class="bold"><strong>data</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> as + before, but construct the <span class="bold"><strong>key</strong></span> + <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and + <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a> with a data size of zero;. + In both cases, set the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag to + <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a>. + </p> + <p> + Alternatively, for btree and hash access methods, + construct a single bulk buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using + <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_KEY_WRITE_NEXT.html" class="olink">DB_MULTIPLE_KEY_WRITE_NEXT</a>. + For recno and queue access methods, construct a bulk + buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> + using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and + <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a>. In both cases, set the + <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag to <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a>. + </p> + <p> + A successful bulk operation is logically equivalent to a loop through + each key/data pair, performing a <a href="../api_reference/C/dbput.html" class="olink">DB->put()</a> for each + one. + </p> </div> <div class="sect2" lang="en" xml:lang="en"> <div class="titlepage"> @@ -221,9 +251,40 @@ rec_display(DB *dbp) </div> </div> </div> - <p>To delete all records with a specified set of keys with the btree or hash access methods, construct a bulk buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_WRITE_NEXT.html" class="olink">DB_MULTIPLE_WRITE_NEXT</a>. To delete a set of records with the recno or queue access methods, construct the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a> with a data size of zero. In both cases, set the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag to <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a>. This is equivalent to calling <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a> for each key in the bulk buffer. In particular, if the database supports duplicates, all records with the matching key are deleted.</p> - <p>Alternatively, to delete a specific set of key/data pairs, which may be items within a set of duplicates, there are also two cases depending on whether the access method uses record numbers for keys. For btree and hash access methods, construct a single bulk buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_KEY_WRITE_NEXT.html" class="olink">DB_MULTIPLE_KEY_WRITE_NEXT</a>. For recno and queue access methods, construct a bulk buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a>. In both cases, set the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag to <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a>.</p> - <p>A successful bulk operation is logically equivalent to a loop through each key/data pair, performing a <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a> for each one.</p> + <p> + To delete all records with a specified set of keys with + the btree or hash access methods, construct a bulk buffer + in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using + <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_WRITE_NEXT.html" class="olink">DB_MULTIPLE_WRITE_NEXT</a>. To + delete a set of records with the recno or queue access + methods, construct the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using + <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and + <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a> with a data size of zero. + In both cases, set the <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE" class="olink">DB_MULTIPLE</a> flag to <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a>. This + is equivalent to calling <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a> for each key in the bulk + buffer. In particular, if the database supports + duplicates, all records with the matching key are + deleted. + </p> + <p> + Alternatively, to delete a specific set of key/data + pairs, which may be items within a set of duplicates, + there are also two cases depending on whether the access + method uses record numbers for keys. For btree and hash + access methods, construct a single bulk buffer in the + <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> using + <a href="../api_reference/C/DB_MULTIPLE_WRITE_INIT.html" class="olink">DB_MULTIPLE_WRITE_INIT</a> and <a href="../api_reference/C/DB_MULTIPLE_KEY_WRITE_NEXT.html" class="olink">DB_MULTIPLE_KEY_WRITE_NEXT</a>. + For recno and queue access methods, construct a bulk + buffer in the <span class="bold"><strong>key</strong></span> <a href="../api_reference/C/dbt.html" class="olink">DBT</a> + using <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_INIT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_INIT</a> and + <a href="../api_reference/C/DB_MULTIPLE_RECNO_WRITE_NEXT.html" class="olink">DB_MULTIPLE_RECNO_WRITE_NEXT</a>. In both cases, set the + <a href="../api_reference/C/dbcget.html#dbcget_DB_MULTIPLE_KEY" class="olink">DB_MULTIPLE_KEY</a> flag to <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a>. + </p> + <p> + A successful bulk operation is logically equivalent to a + loop through each key/data pair, performing a <a href="../api_reference/C/dbdel.html" class="olink">DB->del()</a> for + each one. + </p> </div> </div> <div class="navfooter"> @@ -237,13 +298,12 @@ rec_display(DB *dbp) <td width="40%" align="right"> <a accesskey="n" href="am_misc_partial.html">Next</a></td> </tr> <tr> - <td width="40%" align="left" valign="top">Chapter 4. - Access Method Wrapup - </td> + <td width="40%" align="left" valign="top">Chapter 4. Access Method Wrapup </td> <td width="20%" align="center"> <a accesskey="h" href="index.html">Home</a> </td> - <td width="40%" align="right" valign="top"> Partial record storage and retrieval</td> + <td width="40%" align="right" valign="top"> Partial record storage and + retrieval</td> </tr> </table> </div> |