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1 files changed, 61 insertions, 46 deletions
diff --git a/docs/programmer_reference/am_conf_logrec.html b/docs/programmer_reference/am_conf_logrec.html index 9f72bcc5..68906418 100644 --- a/docs/programmer_reference/am_conf_logrec.html +++ b/docs/programmer_reference/am_conf_logrec.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_conf_select.html">Prev</a> </td> - <th width="60%" align="center">Chapter 2. - Access Method Configuration - </th> + <th width="60%" align="center">Chapter 2. Access Method Configuration </th> <td width="20%" align="right"> <a accesskey="n" href="general_am_conf.html">Next</a></td> </tr> </table> @@ -38,49 +36,66 @@ </div> </div> </div> - <p>The Berkeley DB Btree, Queue and Recno access methods can operate on logical -record numbers. Record numbers are 1-based, not 0-based, that is, the -first record in a database is record number 1.</p> - <p>In all cases for the Queue and Recno access methods, and when calling -the Btree access method using the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> and <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> methods -with the <a href="../api_reference/C/dbget.html#dbget_DB_SET_RECNO" class="olink">DB_SET_RECNO</a> flag specified, the <span class="bold"><strong>data</strong></span> field of -the key <a href="../api_reference/C/dbt.html" class="olink">DBT</a> must be a pointer to a memory location of type -<span class="bold"><strong>db_recno_t</strong></span>, as typedef'd in the standard Berkeley DB include file. -The <span class="bold"><strong>size</strong></span> field of the key <a href="../api_reference/C/dbt.html" class="olink">DBT</a> should be the size of that -type (for example, "sizeof(db_recno_t)" in the C programming language). -The <span class="bold"><strong>db_recno_t</strong></span> type is a 32-bit unsigned type, which limits the -number of logical records in a Queue or Recno database, and the maximum -logical record which may be directly retrieved from a Btree database, -to 4,294,967,295.</p> - <p>Record numbers in Recno databases can be configured to run in either -mutable or fixed mode: mutable, where logical record numbers change as -records are deleted or inserted, and fixed, where record numbers never -change regardless of the database operation. Record numbers in Queue -databases are always fixed, and never change regardless of the database -operation. Record numbers in Btree databases are always mutable, and -as records are deleted or inserted, the logical record number for other -records in the database can change. See -<a class="xref" href="rq_conf.html#am_conf_renumber" title="Logically renumbering records">Logically renumbering records</a> -for more information.</p> - <p>When appending new data items into Queue databases, record numbers wrap -around. When the tail of the queue reaches the maximum record number, -the next record appended will be given record number 1. If the head of -the queue ever catches up to the tail of the queue, Berkeley DB will return -the system error EFBIG. Record numbers do not wrap around when appending -new data items into Recno databases.</p> - <p>Configuring Btree databases to support record numbers can severely limit -the throughput of applications with multiple concurrent threads writing -the database, because locations used to store record counts often become -hot spots that many different threads all need to update. In the case -of a Btree supporting duplicate data items, the logical record number -refers to a key and all of its data items, as duplicate data items are -not individually numbered.</p> - <p>The following is an example function that reads records from standard -input and stores them into a Recno database. The function then uses a -cursor to step through the database and display the stored records.</p> + <p> + The Berkeley DB Btree, Queue and Recno access methods can + operate on logical record numbers. Record numbers are 1-based, + not 0-based, that is, the first record in a database is record + number 1. + </p> + <p> + In all cases for the Queue and Recno access methods, and + when calling the Btree access method using the <a href="../api_reference/C/dbget.html" class="olink">DB->get()</a> and + <a href="../api_reference/C/dbcget.html" class="olink">DBC->get()</a> methods with the <a href="../api_reference/C/dbget.html#dbget_DB_SET_RECNO" class="olink">DB_SET_RECNO</a> flag specified, + the <span class="bold"><strong>data</strong></span> field of the key + <a href="../api_reference/C/dbt.html" class="olink">DBT</a> must be a pointer to a memory location of type <span class="bold"><strong>db_recno_t</strong></span>, as typedef'd in the + standard Berkeley DB include file. The <span class="bold"><strong>size + </strong></span> field of the key <a href="../api_reference/C/dbt.html" class="olink">DBT</a> should be the size + of that type (for example, "sizeof(db_recno_t)" in the C + programming language). The <span class="bold"><strong>db_recno_t</strong></span> + type is a 32-bit unsigned type, which limits the number of logical + records in a Queue or Recno database, and the maximum logical record + which may be directly retrieved from a Btree database, to 4,294,967,295. + </p> + <p> + Record numbers in Recno databases can be configured to run + in either mutable or fixed mode: mutable, where logical record + numbers change as records are deleted or inserted, and fixed, + where record numbers never change regardless of the database + operation. Record numbers in Queue databases are always fixed, + and never change regardless of the database operation. Record + numbers in Btree databases are always mutable, and as records + are deleted or inserted, the logical record number for other + records in the database can change. See <a class="xref" href="rq_conf.html#am_conf_renumber" title="Logically renumbering records">Logically renumbering + records</a> for more + information. + </p> + <p> + When appending new data items into Queue databases, record + numbers wrap around. When the tail of the queue reaches the + maximum record number, the next record appended will be given + record number 1. If the head of the queue ever catches up to + the tail of the queue, Berkeley DB will return the system + error EFBIG. Record numbers do not wrap around when appending + new data items into Recno databases. + </p> + <p> + Configuring Btree databases to support record numbers can + severely limit the throughput of applications with multiple + concurrent threads writing the database, because locations + used to store record counts often become hot spots that many + different threads all need to update. In the case of a Btree + supporting duplicate data items, the logical record number + refers to a key and all of its data items, as duplicate data + items are not individually numbered. + </p> + <p> + The following is an example function that reads records from + standard input and stores them into a Recno database. The + function then uses a cursor to step through the database and + display the stored records. + </p> <a id="prog_am1"></a> - <pre class="programlisting"> -int + <pre class="programlisting">int recno_build(DB *dbp) { DBC *dbcp; |