PostgreSQL 9.4 Beta 3 发布，此版本包括所有 PostgreSQL 9.4 版本的特性预览，同时还修复了 beta 2 版本发现的一些 bug。
PostgreSQL 9.4 Beta 3 最主要的改进是 JSONB 数据类型格式的修改，为了 JSONB 字段更好压缩，减少存储方面的要求。请注意，这个改进向后不兼容，所以用户在 Beta 1 和 Beta 2 加载到 JSONB 字段的数据需要 pg_dump 或者重新存储升级到 Beta 3。
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Rename pg_recvlogical's --create/--drop to --create-slot/--drop-slot
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Prevent unbounded delay when starting background worker
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Remove num_xloginsert_locks GUC, replace with a #define
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Fix pg_dump's --if-exists for large objects
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Remove ban on zero length JSON object keys
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Return NULL from json_object_agg if it gets no rows
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Log ALTER SYSTEM statements as DDL
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Fix failure of contrib/auto_explain to print per-node timing information
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Multiple fixes for TAP checks
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Support ALTER SYSTEM RESET command
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Fix power_var_int() for large integer exponents
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Fix vacuumdb --analyze-in-stages --all order
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Change the way latency is calculated with pgbench --rate option
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Support ALTER ... ALL IN with event triggers
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Remove superuser-only restriction from pg_is_xlog_replay_paused()
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Fix FOR UPDATE NOWAIT on updated tuple chains
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Fix Var handling for security barrier views
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Fix superuser concurrent refresh of matview owned by another
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Don't track DEALLOCATE in pg_stat_statements
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Fix corner-case behaviors in JSON/JSONB field extraction operators
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Change the way pg_basebackup's tablespace mapping is implemented
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Rework 'MOVE ALL' to 'ALTER .. ALL IN TABLESPACE'
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Fix core dump in jsonb #> operator
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Revert psql changes to support wrapped expanded mode
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Expose -S option in pg_receivexlog
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Reject duplicate column names in foreign key referenced-columns lists
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Fix checkpointer crash
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Many minor fixes to JSON and JSONB functionality
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Many minor fixes to logical decoding
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Multiple bug fixes for older issues to be included in an upcoming minor release.
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More documentation improvements and changes
更多更新内容请看发行说明，其他更多新特性请看 9.4 Features Wiki Page.
PostgreSQL (也叫 Postgres)是一个自由的对象-关系数据库服务器(数据库管理系统)，它在灵活的 BSD-风格许可证下发行。它提供了相对其他开放源代码数据库系统(比如 MySQL 和 Firebird)，和对专有系统比如 Oracle、Sybase、IBM 的 DB2 和 Microsoft SQL Server的一种选择。
PostgreSQL 不寻常的名字导致一些读者停下来尝试拼读它，特别是那些把SQL拼读为"sequel"的人。PostgreSQL 开发者把它拼读为 "post-gress-Q-L"。(Audio sample, 5.6k MP3)。它也经常被简略念为 "postgres"。
