摘要：背景 在 Oracle 中用户在 drop table 的时候，表文件并不会从磁盘上移除，而是表被重命名为一个特殊的名字，然后用系统表记录。该功能被称为回收站功能。和 Windows 回收站类似，用户可以从回收站中恢复删除的表。 在 Lightdb 24.2 中支持了该功能。 参考： Oracle 阅读全文

摘要：(From chatgpt) A simple SELECT query in PostgreSQL operates under the MVCC (Multi-Version Concurrency Control) model, which allows it to read data wit 阅读全文

摘要：Garbage Collection The following example comes from the test case TxnExecutorTest_GarbageCollection: Before the first garbage collection, When txn_wat 阅读全文

摘要：The email lists: may be a buffer overflow problem [ecpg bug]: can not use single '*' in multi-line comment after c preprocessor directives 阅读全文

摘要：References https://www.geeksforgeeks.org/extendible-hashing-dynamic-approach-to-dbms/ examples walkthrough in detail https://medium.com/@redixhumayun/ 阅读全文

摘要：1 起因是想玩玩 opengauss 的回收站功能。结果根据 opengauss 官方网站，根本试玩不了。 想从源码编译安装 opengauss，结果官方网站文档又不行！ 最后还是靠非官方的这篇文章才能安装成功。 2 根据官网描述，需要在 postgresql.conf 里新增 enable_rec 阅读全文

摘要：(classid,objid,objsubid) depends on (refclassid,refobjid,refobjsubid). -- which objects does relation 88088 depends on select * from pg_depend where c 阅读全文

摘要：System Table Name Brief Description Related Views SYS.OBJ$ Contains information about all database objects USER_OBJECTS, ALL_OBJECTS, DBA_OBJECTS SYS. 阅读全文

摘要：How does sig_atomic_t actually work? Key Takeways: sig_atomic_t is not an atomic data type used in the context of a signal handler An integral type th 阅读全文

摘要：kinds of frame definition implementation https://ldd.cool/pdf/windowagg.pdf 阅读全文

摘要：From comments of struct JunkFilter: A junk attribute is an attribute in a tuple that is needed only for storing intermediate information in the execut 阅读全文

摘要：https://www.postgresql.eu/events/pgconfeu2017/schedule/session/1585-be-pro-activ-on-postgresql-performance/ https://www.postgresql.eu/events/pgconfeu2 阅读全文

摘要：What NamedTuplestore 按字面意思理解，就是一个有名字的 tuplestore, 那估计就不是一个正常的表。根据 PostgreSQL 的官方叫法，NamedTuplestoreScan 对应的表称为 Ephemeral Named Relation， 中文翻译为 短暂的命名关系. 阅读全文

摘要：One sentence summary A temporary table could reside within a temporary tablespace, utilizing a temporary name in a temporary schema or namespace. More 阅读全文

摘要：The following sql statements will trigger calling function GetExistingLocalJoinPath. setup CREATE EXTENSION postgres_fdw; CREATE SERVER foreign_server 阅读全文

摘要：The SQL select sum(sum(a)) from myt1 group by a; This note focuses only on sum(sum(a)) and it's about how postgres rejects the sql above. Notes sum(su 阅读全文

摘要：This note will introduce the workflow of parse.pl of the ecpg precompiler. Run the precompiler: perl parse.pl . ../../../backend/parser/gram.y workflo 阅读全文

摘要：背景 在如下的 sql 中， select rowid from (select 1 from t); lightdb 24.1 以前会直接报错，说找不到 rowid 列。为了兼容 Oracle, 在 24.1 中，我们选择将告知子查询除了返回子查询应有的列之外，还需返回 rowid 列。 样例 以 阅读全文

摘要：The SQL select a from (select a from t); Overview from (select a from t) will map to one RangeTblEntry struct of the outter query. from t will map to 阅读全文