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new 8e048a74791 Update _index.en.md (#19426)
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commit 8e048a7479173d9fd88a6ee4a867ff969d6cdb93
Author: Mike0601 <[email protected]>
AuthorDate: Thu Jul 21 16:21:50 2022 +0800
Update _index.en.md (#19426)
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@@ -5,25 +5,148 @@ weight = 1
chapter = true
+++
-## Background
+## Definition
-With information technology innovating, more and more applications established
in the new fields, prompt and push evolution of human society's cooperation
mode.
-Data is increasing explosively, the data storage and computing method are
facing innovation all the time.
+Thanks to the innovation of information technology, and fast application
iteration speed, data traffic is growing exponentially - ultimately
continuously changing data storage and computation models.
-Transaction, big data, association analysis, Internet of things and other
scenarios subdivided quickly, a single database can not apply to all
application scenarios anymore.
-At the same time, the internal of scenario is becoming more and more detailed,
and it has become normal for similar scenarios to use different databases.
+Transaction-oriented, Big Data, IoT, and other scenarios are increasingly
fragmented, indicating that a single database can no longer be applied to all
circumstances. At the same time, things are getting more and more
sophisticated, so it becomes the norm to use different databases for similar
scenarios. This shows that database fragmentation has already become an
irreversible trend.
-The trend of database fragmentation is coming.
+Database compatibility mainly refers to the compatibility of elements like
syntax, and protocols for many fragmented databases.
-## Challenges
+## Relevant Concepts
-There is no unified database access protocol and SQL dialect,
-as well as the maintenance and monitoring methods differences by various
databases,
-learning and maintenance cost of developers and DBAs are increasing rapidly.
-Improving the compatibility with the original database is the premise of
providing incremental services on it.
+### SQL (Structured Query Language)
-The compatibility between SQL dialect and database protocol is the key point
to improve database compatibility.
+SQL is a language used to manage databases and became an American National
Standards Institute (ANSI) standard in 1986 and a standard established by
International Organization for Standardization (ISO) standard in 1987 [13].
Since then, this standard has undergone a series of updates to include several
new features. Despite its presence, most databases have their unique languages
besides SQL, which may lead to different dialects depending on the specific
database system.
-## Goal
+### Database Protocols
-**The goal of database compatibility for Apache ShardingSphere is make user
feel nothing changed among various original databases.**
+It is possible to deploy data products for client-server communication. Just
like SQL, different databases, or even different versions of the same database,
support different communication protocols, so accessing many different
databases with the same protocol is impossible.
+
+## Limitations
+
+### SQL Parsing
+
+SQL is the standard language for users to communicate with the database. The
SQL parsing engine is responsible for parsing SQL strings into abstract syntax
trees for Apache ShardingSphere to understand and implement its incremental
functionality.
+
+MySQL, PostgreSQL, SQLServer, Oracle, openGauss, and SQL92 compliant SQL
dialects are currently supported. Due to the complexity of SQL syntax, there
are still a few SQL currently not supported.
+
+This section lists those SQL types in detail for users' reference.
+
+You are welcome to add anything not covered in the list, and we will work hard
to support these in future versions as soon as possible.
+
+Source code:
https://github.com/apache/shardingsphere/tree/master/shardingsphere-sql-parser
+
+#### MySQL
+
+SQL not supported are listed below:
+
+|SQL|
+|---|
+|CLONE LOCAL DATA DIRECTORY = ‘clone_dir’|
+|INSTALL COMPONENT ‘file://component1’, ‘file://component2’|
+|UNINSTALL COMPONENT ‘file://component1’, ‘file://component2’|
+|REPAIR TABLE t_order|
+|OPTIMIZE TABLE t_order|
+|CHECKSUM TABLE t_order|
+|CHECK TABLE t_order|
+|SET RESOURCE GROUP group_name|
+|DROP RESOURCE GROUP group_name|
+|CREATE RESOURCE GROUP group_name TYPE = SYSTEM|
+|ALTER RESOURCE GROUP rg1 VCPU = 0-63|
+
+Source
Code：https://github.com/apache/shardingsphere/tree/master/shardingsphere-sql-parser/shardingsphere-sql-parser-dialect/shardingsphere-sql-parser-mysql
+
+
+#### openGauss
+
+SQL not supported are listed below:
+
+|SQL|
+|---|
+|CREATE type avg_state AS (total bigint, count bigint);|
+|CREATE AGGREGATE my_avg(int4) (stype = avg_state, sfunc = avg_transfn,
finalfunc = avg_finalfn)|
+|CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g;|
+|CREATE SCHEMA alt_nsp1;|
+|ALTER AGGREGATE alt_agg3(int) OWNER TO regress_alter_generic_user2;|
+|CREATE CONVERSION alt_conv1 FOR ‘LATIN1’ TO ‘UTF8’ FROM iso8859_1_to_utf8;|
+|CREATE FOREIGN DATA WRAPPER alt_fdw1|
+|CREATE SERVER alt_fserv1 FOREIGN DATA WRAPPER alt_fdw1|
+|CREATE LANGUAGE alt_lang1 HANDLER plpgsql_call_handler|
+|CREATE STATISTICS alt_stat1 ON a, b FROM alt_regress_1|
+|CREATE TEXT SEARCH DICTIONARY alt_ts_dict1 (template=simple)|
+|CREATE RULE def_view_test_ins AS ON INSERT TO def_view_test DO INSTEAD INSERT
INTO def_test SELECT new.*|
+|ALTER TABLE alterlock SET (toast.autovacuum_enabled = off)|
+|CREATE PUBLICATION pub1 FOR TABLE alter1.t1, ALL TABLES IN SCHEMA alter2|
+
+Source
code：https://github.com/apache/shardingsphere/tree/master/shardingsphere-sql-parser/shardingsphere-sql-parser-dialect/shardingsphere-sql-parser-opengauss
+
+#### PostgreSQL
+
+SQL not supported are listed below:
+
+|SQL|
+|---|
+|CREATE type avg_state AS (total bigint, count bigint);|
+|CREATE AGGREGATE my_avg(int4) (stype = avg_state, sfunc = avg_transfn,
finalfunc = avg_finalfn)|
+|CREATE TABLE agg_data_2k AS SELECT g FROM generate_series(0, 1999) g;|
+|CREATE SCHEMA alt_nsp1;|
+|ALTER AGGREGATE alt_agg3(int) OWNER TO regress_alter_generic_user2;|
+|CREATE CONVERSION alt_conv1 FOR ‘LATIN1’ TO ‘UTF8’ FROM iso8859_1_to_utf8;|
+|CREATE FOREIGN DATA WRAPPER alt_fdw1|
+|CREATE SERVER alt_fserv1 FOREIGN DATA WRAPPER alt_fdw1|
+|CREATE LANGUAGE alt_lang1 HANDLER plpgsql_call_handler|
+|CREATE STATISTICS alt_stat1 ON a, b FROM alt_regress_1|
+|CREATE TEXT SEARCH DICTIONARY alt_ts_dict1 (template=simple)|
+|CREATE RULE def_view_test_ins AS ON INSERT TO def_view_test DO INSTEAD INSERT
INTO def_test SELECT new.*|
+|ALTER TABLE alterlock SET (toast.autovacuum_enabled = off)|
+|CREATE PUBLICATION pub1 FOR TABLE alter1.t1, ALL TABLES IN SCHEMA alter2|
+
+Source Code:
https://github.com/apache/shardingsphere/tree/master/shardingsphere-sql-parser/shardingsphere-sql-parser-dialect/shardingsphere-sql-parser-postgresql
+
+
+### Database Protocols
+
+Apache ShardingSphere currently implements MySQL and PostgreSQL protocols
+Source
Code：https://github.com/apache/shardingsphere/tree/master/shardingsphere-db-protocol
+
+### Features Supported
+
+Apache ShardingSphere provides distributed collaboration capabilities for
databases while abstracting some of the features of the database to the upper
layer for integrated management to make it easier for users.
+
+Therefore, for features provided universally, native SQL will no longer be
sent down to the database and will send out a notice saying that the operation
is not supported. Users can just rely on the methods provided by ShardingSphere
instead.
+
+This section provides a detailed list of currently unsupported database
features and related SQL statements for further reference.
+
+Feel free to add any SQL that is not covered in this section.
+
+#### MySQL
+
+MySQL does not support this SQL listed below:
+
+**User&Role**
+
+|SQL|
+|---|
+|CREATE USER ‘finley’@‘localhost’ IDENTIFIED BY ‘password’|
+|ALTER USER ‘finley’@‘localhost’ IDENTIFIED BY ‘new_password’|
+|DROP USER ‘finley’@‘localhost’;|
+|CREATE ROLE ‘app_read’|
+|DROP ROLE ‘app_read’|
+|SHOW CREATE USER finley|
+|SET PASSWORD = ‘auth_string’|
+|SET ROLE DEFAULT;|
+
+**Permission**
+
+|SQL|
+|---|
+|GRANT ALL ON db1.* TO ‘jeffrey’@‘localhost’|
+|GRANT SELECT ON world.* TO ‘role3’;|
+|GRANT ‘role1’, ‘role2’ TO ‘user1’@‘localhost’|
+|REVOKE INSERT ON . FROM ‘jeffrey’@‘localhost’|
+|REVOKE ‘role1’, ‘role2’ FROM ‘user1’@‘localhost’|
+|REVOKE ALL PRIVILEGES, GRANT OPTION FROM user_or_role|
+|SHOW GRANTS FOR ‘jeffrey’@‘localhost’|
+|SHOW GRANTS FOR CURRENT_USER|
+|FLUSH PRIVILEGES|
