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h2/src/docsrc/html/changelog.html
浏览文件 @ 1f12ebf1
......@@ -18,7 +18,8 @@ Change Log
<h1>Change Log</h1>
<h2>Next Version (unreleased)</h2>
<ul><li>-
<ul><li>Database-level connection settings could only be set in the database URL,
but not using the Properties parameter of DriverManaget.getConnection(String url, Properties info).
</li></ul>
<h2>Version 1.3.152 Beta (2011-03-01)</h2>
......
h2/src/docsrc/html/performance.html
浏览文件 @ 1f12ebf1
......@@ -28,10 +28,10 @@ Performance
Application Profiling</a><br />
<a href="#database_profiling">
Database Profiling</a><br />
<a href="#storage_and_indexes">
How Data is Stored and How Indexes Work</a><br />
<a href="#explain_plan">
Statement Execution Plans</a><br />
<a href="#storage_and_indexes">
How Data is Stored and How Indexes Work</a><br />
<a href="#fast_import">
Fast Database Import</a><br />
......@@ -611,6 +611,92 @@ following profiling data (results vary):
-- 0% 100% 0 1 0 SET TRACE_LEVEL_FILE 3;
</pre>
<h2 id="explain_plan">Statement Execution Plans</h2>
<p>
The SQL statement <code>EXPLAIN</code> displays the indexes and optimizations the database uses for a statement.
The following statements support <code>EXPLAIN</code>: <code>SELECT, UPDATE, DELETE, MERGE, INSERT</code>.
The following query shows that the database uses the primary key index to search for rows:
</p>
<pre>
EXPLAIN SELECT * FROM TEST WHERE ID=1;
SELECT
TEST.ID,
TEST.NAME
FROM PUBLIC.TEST
/* PUBLIC.PRIMARY_KEY_2: ID = 1 */
WHERE ID = 1
</pre>
<p>
For joins, the tables in the execution plan are sorted in the order they are processed.
The following query shows the database first processes the table <code>INVOICE</code> (using the primary key).
For each row, it will additionally check that the value of the column <code>AMOUNT</code> is larger than zero,
and for those rows the database will search in the table <code>CUSTOMER</code> (using the primary key).
The query plan contains some redundancy so it is a valid statement.
</p>
<pre>
CREATE TABLE CUSTOMER(ID IDENTITY, NAME VARCHAR);
CREATE TABLE INVOICE(ID IDENTITY,
CUSTOMER_ID INT REFERENCES CUSTOMER(ID),
AMOUNT NUMBER);
EXPLAIN SELECT I.ID, C.NAME FROM CUSTOMER C, INVOICE I
WHERE I.ID=10 AND AMOUNT>0 AND C.ID=I.CUSTOMER_ID;
SELECT
I.ID,
C.NAME
FROM PUBLIC.INVOICE I
/* PUBLIC.PRIMARY_KEY_9: ID = 10 */
/* WHERE (I.ID = 10)
AND (AMOUNT > 0)
*/
INNER JOIN PUBLIC.CUSTOMER C
/* PUBLIC.PRIMARY_KEY_5: ID = I.CUSTOMER_ID */
ON 1=1
WHERE (C.ID = I.CUSTOMER_ID)
AND ((I.ID = 10)
AND (AMOUNT > 0))
</pre>
<h3>Displaying the Scan Count</h3>
<p>
<code>EXPLAIN ANALYZE</code> additionally shows the scanned rows per table and pages read from disk per table or index.
This will actually execute the query, unlike <code>EXPLAIN</code> which only prepares it.
The following query scanned 1000 rows, and to do that had to read 85 pages from the data area of the table.
Running the query twice will not list the pages read from disk, because they are now in the cache.
The <code>tableScan</code> means this query doesn't use an index.
</p>
<pre>
EXPLAIN ANALYZE SELECT * FROM TEST;
SELECT
TEST.ID,
TEST.NAME
FROM PUBLIC.TEST
/* PUBLIC.TEST.tableScan */
/* scanCount: 1000 */
/*
total: 85
TEST.TEST_DATA read: 85 (100%)
*/
</pre>
<h3>Special Optimizations</h3>
<p>
For certain queries, the database doesn't need to read all rows, or doesn't need to sort the result even if <code>ORDER BY</code> is used.
</p><p>
For queries of the form <code>SELECT COUNT(*), MIN(ID), MAX(ID) FROM TEST</code>, the query plan includes the line
<code>/* direct lookup */</code> if the data can be read from an index.
</p><p>
For queries of the form <code>SELECT DISTINCT CUSTOMER_ID FROM INVOICE</code>, the query plan includes the line
<code>/* distinct */</code> if there is an non-unique or multi-column index on this column, and if this column has a low selectivity.
</p><p>
For queries of the form <code>SELECT * FROM TEST ORDER BY ID</code>, the query plan includes the line
<code>/* index sorted */</code> to indicate there is no separate sorting required.
</p><p>
For queries of the form <code>SELECT * FROM TEST GROUP BY ID ORDER BY ID</code>, the query plan includes the line
<code>/* group sorted */</code> to indicate there is no separate sorting required.
</p>
<h2 id="storage_and_indexes">How Data is Stored and How Indexes Work</h2>
<p>
Internally, each row in a table is identified by a unique number, the row id.
......@@ -650,6 +736,8 @@ FROM PUBLIC.ADDRESS
/* PUBLIC.ADDRESS.tableScan */
WHERE NAME = 'Miller';
</pre>
<h3>Indexes</h3>
<p>
An index internally is basically just a table that contains the indexed column(s), plus the row id:
</p>
......@@ -713,7 +801,13 @@ WHERE FIRST_NAME = 'John';
</pre>
<p>
If your application often queries the table for a phone number, then it makes sense to create
an additional index on it, which then contains the following data:
an additional index on it:
</p>
<pre>
CREATE INDEX IDX_PHONE ON ADDRESS(PHONE);
</pre>
<p>
This index contains the phone number, and the row id:
</p>
<table>
<tr><th>PHONE</th><th>_ROWID_</th></tr>
......@@ -721,92 +815,31 @@ an additional index on it, which then contains the following data:
<tr><td>123 456 789</td><td>1</td></tr>
</table>
<h2 id="explain_plan">Statement Execution Plans</h2>
<h3>Using Multiple Indexes</h3>
<p>
The SQL statement <code>EXPLAIN</code> displays the indexes and optimizations the database uses for a statement.
The following statements support <code>EXPLAIN</code>: <code>SELECT, UPDATE, DELETE, MERGE, INSERT</code>.
The following query shows that the database uses the primary key index to search for rows:
Within a query, only one index per logical table is used.
Using the condition <code>PHONE = '123 567 789' OR CITY = 'Berne'</code>
would use a table scan instead of first using the index on the phone number and then the index on the city.
It makes sense to write two queries and combine then using <code>UNION</code>.
In this case, each individual query uses a different index:
</p>
<pre>
EXPLAIN SELECT * FROM TEST WHERE ID=1;
SELECT
TEST.ID,
TEST.NAME
FROM PUBLIC.TEST
/* PUBLIC.PRIMARY_KEY_2: ID = 1 */
WHERE ID = 1
</pre>
<p>
For joins, the tables in the execution plan are sorted in the order they are processed.
The following query shows the database first processes the table <code>INVOICE</code> (using the primary key).
For each row, it will additionally check that the value of the column <code>AMOUNT</code> is larger than zero,
and for those rows the database will search in the table <code>CUSTOMER</code> (using the primary key).
The query plan contains some redundancy so it is a valid statement.
</p>
<pre>
CREATE TABLE CUSTOMER(ID IDENTITY, NAME VARCHAR);
CREATE TABLE INVOICE(ID IDENTITY,
CUSTOMER_ID INT REFERENCES CUSTOMER(ID),
AMOUNT NUMBER);
EXPLAIN SELECT NAME FROM ADDRESS WHERE PHONE = '123 567 789'
UNION SELECT NAME FROM ADDRESS WHERE CITY = 'Berne';
EXPLAIN SELECT I.ID, C.NAME FROM CUSTOMER C, INVOICE I
WHERE I.ID=10 AND AMOUNT>0 AND C.ID=I.CUSTOMER_ID;
SELECT
I.ID,
C.NAME
FROM PUBLIC.INVOICE I
/* PUBLIC.PRIMARY_KEY_9: ID = 10 */
/* WHERE (I.ID = 10)
AND (AMOUNT > 0)
*/
INNER JOIN PUBLIC.CUSTOMER C
/* PUBLIC.PRIMARY_KEY_5: ID = I.CUSTOMER_ID */
ON 1=1
WHERE (C.ID = I.CUSTOMER_ID)
AND ((I.ID = 10)
AND (AMOUNT > 0))
</pre>
<h3>Displaying the Scan Count</h3>
<p>
<code>EXPLAIN ANALYZE</code> additionally shows the scanned rows per table and pages read from disk per table or index.
This will actually execute the query, unlike <code>EXPLAIN</code> which only prepares it.
The following query scanned 1000 rows, and to do that had to read 85 pages from the data area of the table.
Running the query twice will not list the pages read from disk, because they are now in the cache.
The <code>tableScan</code> means this query doesn't use an index.
</p>
<pre>
EXPLAIN ANALYZE SELECT * FROM TEST;
SELECT
TEST.ID,
TEST.NAME
FROM PUBLIC.TEST
/* PUBLIC.TEST.tableScan */
/* scanCount: 1000 */
/*
total: 85
TEST.TEST_DATA read: 85 (100%)
*/
(SELECT
NAME
FROM PUBLIC.ADDRESS
/* PUBLIC.IDX_PHONE: PHONE = '123 567 789' */
WHERE PHONE = '123 567 789')
UNION
(SELECT
NAME
FROM PUBLIC.ADDRESS
/* PUBLIC.INDEX_PLACE: CITY = 'Berne' */
WHERE CITY = 'Berne')
</pre>
<h3>Special Optimizations</h3>
<p>
For certain queries, the database doesn't need to read all rows, or doesn't need to sort the result even if <code>ORDER BY</code> is used.
</p><p>
For queries of the form <code>SELECT COUNT(*), MIN(ID), MAX(ID) FROM TEST</code>, the query plan includes the line
<code>/* direct lookup */</code> if the data can be read from an index.
</p><p>
For queries of the form <code>SELECT DISTINCT CUSTOMER_ID FROM INVOICE</code>, the query plan includes the line
<code>/* distinct */</code> if there is an non-unique or multi-column index on this column, and if this column has a low selectivity.
</p><p>
For queries of the form <code>SELECT * FROM TEST ORDER BY ID</code>, the query plan includes the line
<code>/* index sorted */</code> to indicate there is no separate sorting required.
</p><p>
For queries of the form <code>SELECT * FROM TEST GROUP BY ID ORDER BY ID</code>, the query plan includes the line
<code>/* group sorted */</code> to indicate there is no separate sorting required.
</p>
<h2 id="fast_import">Fast Database Import</h2>
<p>
To speed up large imports, consider using the following options temporarily:
......
h2/src/docsrc/html/roadmap.html
浏览文件 @ 1f12ebf1
......@@ -86,8 +86,6 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Make DDL (Data Definition) operations transactional.
</li><li>RANK() and DENSE_RANK(), Partition using OVER().
</li><li>Set a connection read only (Connection.setReadOnly) or using a connection parameter.
</li><li>Optimizer: use an index for IS NULL and IS NOT NULL (including linked tables).
ID IS NOT NULL could be converted to ID &gt;= Integer.MIN_VALUE.
</li><li>Access rights: finer grained access control (grant access for specific functions).
</li><li>Version check: docs / web console (using Javascript), and maybe in the library (using TCP/IP).
</li><li>Web server classloader: override findResource / getResourceFrom.
......@@ -102,17 +100,14 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Fulltext search (native): reader / tokenizer / filter.
</li><li>Linked schema using CSV files: one schema for a directory of files; support indexes for CSV files.
</li><li>iReport to support H2.
</li><li>Implement missing JDBC API (CallableStatement,...).
</li><li>Compression of the cache.
</li><li>Include SMPT (mail) client (alert on cluster failure, low disk space,...).
</li><li>JSON parser and functions.
</li><li>Server: client ping from time to time (to avoid timeout - is timeout a problem?).
</li><li>Copy database: tool with config GUI and batch mode, extensible (example: compare).
</li><li>Document, implement tool for long running transactions using user-defined compensation statements.
</li><li>Support SET TABLE DUAL READONLY.
</li><li>GCJ: what is the state now?
</li><li>Events for: database Startup, Connections, Login attempts, Disconnections, Prepare (after parsing), Web Server. See http://docs.openlinksw.com/virtuoso/fn_dbev_startup.html
</li><li>Optimization: log compression.
</li><li>Optimization: simpler log compression.
</li><li>ROW_NUMBER() OVER([ORDER BY columnName]).
</li><li>Support standard INFORMATION_SCHEMA tables, as defined in http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt - specially KEY_COLUMN_USAGE: http://dev.mysql.com/doc/refman/5.0/en/information-schema.html, http://www.xcdsql.org/Misc/INFORMATION_SCHEMA%20With%20Rolenames.gif
</li><li>Compatibility: in MySQL, HSQLDB, /0.0 is NULL; in PostgreSQL, Derby: division by zero.
......@@ -120,10 +115,9 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Custom class loader to reload functions on demand.
</li><li>Clustering: when a database is back alive, automatically synchronize with the master.
</li><li>Test http://mysql-je.sourceforge.net/
</li><li>Performance: automatically build in-memory indexes if the whole table is in memory.
</li><li>H2 Console: the webclient could support more features like phpMyAdmin.
</li><li>Database file name suffix: a way to use no or a different suffix (for example using a slash).
</li><li>Use Janino to convert Java to C++.
</li><li>Work on the Java to C converter.
</li><li>The HELP information schema can be directly exposed in the Console.
</li><li>Maybe use the 0x1234 notation for binary fields, see MS SQL Server.
</li><li>Support Oracle CONNECT BY in some way: http://www.adp-gmbh.ch/ora/sql/connect_by.html http://philip.greenspun.com/sql/trees.html
......@@ -148,8 +142,6 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Console: improve editing data (Tab, Shift-Tab, Enter, Up, Down, Shift+Del?).
</li><li>Console: autocomplete Ctrl+Space inserts template.
</li><li>Option to encrypt .trace.db file.
</li><li>Write Behind Cache on SATA leads to data corruption See also http://sr5tech.com/write_back_cache_experiments.htm and http://www.jasonbrome.com/blog/archives/2004/04/03/writecache_enabled.html
</li><li>Functions with unknown return or parameter data types: serialize / deserialize.
</li><li>Auto-Update feature for database, .jar file.
</li><li>ResultSet SimpleResultSet.readFromURL(String url): id varchar, state varchar, released timestamp.
</li><li>Partial indexing (see PostgreSQL).
......@@ -167,16 +159,14 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Implement Clob / Blob truncate and the remaining functionality.
</li><li>Tree join functionality.
</li><li>Add multiple columns at the same time with ALTER TABLE .. ADD .. ADD ...
</li><li>Use JDK 1.4 file locking for the database file and for the lock file (but not yet by default); writing a system property to detect concurrent access from the same VM (different classloaders).
</li><li>File locking: writing a system property to detect concurrent access from the same VM (different classloaders).
</li><li>Pure SQL triggers (example: update parent table if the child table is changed).
</li><li>Add H2 to Gem (Ruby install system).
</li><li>Order conditions inside AND / OR to optimize the performance.
</li><li>Support Oracle functions: TRUNC, NVL2, TO_CHAR, TO_DATE, TO_NUMBER.
</li><li>Support linked JCR tables.
</li><li>Read InputStream when executing, as late as possible (maybe only embedded mode). Problem with re-execute.
</li><li>Native fulltext search: min word length; store word positions.
</li><li>Add an option to the SCRIPT command to generate only portable / standard SQL.
</li><li>Updatable Views (simple cases first).
</li><li>Updatable views: create 'instead of' triggers automatically if possible (simple cases first).
</li><li>Improve create index performance.
</li><li>Compact databases without having to close the database (vacuum).
</li><li>Implement more JDBC 4.0 features.
......@@ -186,28 +176,21 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Public interface for functions (not public static).
</li><li>Support reading the transaction log.
</li><li>Support GRANT SELECT, UPDATE ON *.
</li><li>Eliminate undo log records if stored on disk (just one pointer per block, not per record).
</li><li>Feature matrix as in <a href="http://www.inetsoftware.de/products/jdbc/mssql/features/default.asp">i-net software</a>.
</li><li>Updatable result set on table without primary key or unique index.
</li><li>Compatibility with Derby and PostgreSQL: VALUES(1), (2); SELECT * FROM (VALUES (1), (2)) AS myTable(c1). Issue 221.
</li><li>Use LinkedList instead of ArrayList where applicable.
</li><li>Allow execution time prepare for SELECT * FROM CSVREAD(?, 'columnNameString')
</li><li>Support data type INTERVAL
</li><li>Support % operator (modulo).
</li><li>Support JMX: create an MBean for each database and server (support JConsole).
See http://thedevcloud.blogspot.com/2008/10/displaying-hsql-database-manager-in.html
http://java.sun.com/j2se/1.5.0/docs/api/java/lang/management/ManagementFactory.html#getPlatformMBeanServer()
http://java.sun.com/j2se/1.5.0/docs/guide/management/agent.html
</li><li>Support nested transactions.
</li><li>Add a benchmark for big databases, and one for many users.
</li><li>Compression in the result set (repeating values in the same column) over TCP/IP.
</li><li>Support nested transactions (possibly using savepoints internally).
</li><li>Add a benchmark for bigger databases, and one for many users.
</li><li>Compression in the result set over TCP/IP.
</li><li>Support curtimestamp (like curtime, curdate).
</li><li>Support ANALYZE {TABLE|INDEX} tableName COMPUTE|ESTIMATE|DELETE STATISTICS ptnOption options.
</li><li>Release locks (shared or exclusive) on demand
</li><li>Support OUTER UNION
</li><li>Support parameterized views (similar to CSVREAD, but using just SQL for the definition)
</li><li>A way (JDBC driver) to map an URL (jdbc:h2map:c1) to a connection object
</li><li>Support linked tables to the current database
</li><li>Support dynamic linked schema (automatically adding/updating/removing tables)
</li><li>Clustering: adding a node should be very fast and without interrupting clients (very short lock)
</li><li>Compatibility: # is the start of a single line comment (MySQL) but date quote (Access). Mode specific
......@@ -241,7 +224,7 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>DISTINCT: support large result sets by sorting on all columns (additionally) and then removing duplicates.
</li><li>Support a special trigger on all tables to allow building a transaction log reader.
</li><li>File system with a background writer thread; test if this is faster
</li><li>Better document the source code
</li><li>Better document the source code (high level documentation).
</li><li>Support select * from dual a left join dual b on b.x=(select max(x) from dual)
</li><li>Optimization: don't lock when the database is read-only
</li><li>Issue 146: Support merge join.
......@@ -253,8 +236,8 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Native search: support "phrase search", wildcard search (* and ?), case-insensitive search, boolean operators, and grouping
</li><li>Improve documentation of access rights.
</li><li>Support opening a database that is in the classpath, maybe using a new file system. Workaround: detect jar file using getClass().getProtectionDomain().getCodeSource().getLocation().
</li><li>Support ENUM data type (see MySQL, PostgreSQL, MS SQL Server, maybe others)
</li><li>Remember the user defined data type (domain) of a column
</li><li>Support ENUM data type (see MySQL, PostgreSQL, MS SQL Server, maybe others).
</li><li>Remember the user defined data type (domain) of a column.
</li><li>MVCC: support multi-threaded kernel with multi-version concurrency.
</li><li>Support Jackcess (MS Access databases)
</li><li>Built-in methods to write large objects (BLOB and CLOB): FILE_WRITE('test.txt', 'Hello World')
......@@ -276,11 +259,9 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Recovery should work with encrypted databases
</li><li>Corruption: new error code, add help
</li><li>Space reuse: after init, scan all storages and free those that don't belong to a live database object
</li><li>Use FilterIn / FilterOut putStream?
</li><li>Access rights: add missing features (users should be 'owner' of objects; missing rights for sequences; dropping objects)
</li><li>Support NOCACHE table option (Oracle).
</li><li>Support table partitioning.
</li><li>Index usage for UPDATE ... WHERE .. IN (SELECT...)
</li><li>Add regular javadocs (using the default doclet, but another css) to the homepage.
</li><li>The database should be kept open for a longer time when using the server mode.
</li><li>Javadocs: for each tool, add a copy &amp; paste sample in the class level.
......@@ -289,7 +270,6 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>MySQL compatibility: real SQL statement for DESCRIBE TEST
</li><li>Use a default delay of 1 second before closing a database.
</li><li>Write (log) to system table before adding to internal data structures.
</li><li>Doclet (javadocs): constructors are not listed.
</li><li>Support direct lookup for MIN and MAX when using WHERE (see todo.txt / Direct Lookup).
</li><li>Support other array types (String[], double[]) in PreparedStatement.setObject(int, Object);
</li><li>MVCC should not be memory bound (uncommitted data is kept in memory in the delta index; maybe using a regular b-tree index solves the problem).
......@@ -306,7 +286,6 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Linked tables: make hidden columns available (Oracle: rowid and ora_rowscn columns).
</li><li>H2 Console: in-place autocomplete.
</li><li>Support large databases: split database files to multiple directories / disks (similar to tablespaces).
</li><li>Support to assign a primary key index a user defined name.
</li><li>H2 Console: support configuration option for fixed width (monospace) font.
</li><li>Native fulltext search: support analyzers (specially for Chinese, Japanese).
</li><li>Automatically compact databases from time to time (as a background process).
......@@ -320,7 +299,7 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Applets: support read-only databases in a zip file (accessed as a resource).
</li><li>Long running queries / errors / trace system table.
</li><li>H2 Console should support JaQu directly.
</li><li>Document FTL_SEARCH, FTL_SEARCH_DATA.
</li><li>Better document FTL_SEARCH, FTL_SEARCH_DATA.
</li><li>Sequences: CURRVAL should be session specific. Compatibility with PostgreSQL.
</li><li>Auto-server: add option to define the IP address range or list.
</li><li>Index creation using deterministic functions.
......@@ -330,7 +309,6 @@ See also <a href="build.html#providing_patches">Providing Patches</a>.
</li><li>Avoid using java.util.Calendar internally because it's slow, complicated, and buggy.
</li><li>Support TRUNCATE .. CASCADE like PostgreSQL.
</li><li>Fulltext search: lazy result generation using SimpleRowSource.
</li><li>Support transformation to join for user defined functions, as for IN(SELECT...).
</li><li>Fulltext search: support alternative syntax: WHERE FTL_CONTAINS(name, 'hello').
</li><li>MySQL compatibility: support REPLACE, see http://dev.mysql.com/doc/refman/6.0/en/replace.html and issue 73.
</li><li>MySQL compatibility: support INSERT INTO table SET column1 = value1, column2 = value2
......
h2/src/docsrc/html/tutorial.html
浏览文件 @ 1f12ebf1
......@@ -549,8 +549,11 @@ You can rename it to <code>H2Dialect.java</code> and include this as a patch in
or upgrade to a version of Hibernate where this is fixed.
</p>
<p>
When using compatibility modes such as <code>MODE=MySQL</code> when using Hibernate
is not supported when using <code>H2Dialect</code>.
When using Hibernate, try to use the <code>H2Dialect</code> if possible.
When using the <code>H2Dialect</code>,
compatibility modes such as <code>MODE=MySQL</code> are not supported.
When using such a compatibility mode, use the Hibernate dialect for the
corresponding database instead of the <code>H2Dialect</code>.
</p>
<h2 id="using_toplink">Using TopLink and Glassfish</h2>
......
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