Importing Bookmark Files for Scanned PDFs

从 FreeMdict Forum 下载的扫描电子书,发帖人提到了书签文件可以用来查找,这个想法是我之前没有想到的。尝试用 pdftk-java 来导入书签文件。 brew install pdftk-java 书签文件如下的格式,相同...

November 14, 2023 1110 words 3 min

Note-taking and GTD with Emacs

得益于 Emacs 的扩展性,丰富的插件生态,我构建的笔记和 GTD 流程是杂糅在一起的。并没有完全遵照「卡片笔记法」或 GTD 的流程,其中也有不完善的地方,在不断地...

August 3, 2023 2792 words 6 min


Misc Templatemaker 制作各种纸盒的教程,可以选择对应的例子下载剪裁的 PDF。 Wi-Phi – Wireless Philosophy 很赞的网站:Wireless Philosophy,简称 Wi-Phi ,一个开放的哲学...

August 3, 2023 637 words 2 min

Clustered Indexes / Index Organized Tables (IOT)

Some databases can indeed use an index as primary table store. The Oracle database calls this concept index-organized tables (IOT), other databases use the term clustered index. In this section, both terms are used to either put the emphasis on the table or the index characteristics as needed. An index-organized table is thus a B-tree index without a heap table. This results in two benefits: (1) it saves the space...

May 14, 2023 493 words 1 min

Secondary Indexes

除主键外的其他列上新建的索引都是二级索引。 二级索引的排序与物理记录的排序不一致,存储的是该列本身排序后的值和主键。

May 14, 2023 57 words 1 min

Table access by index rowid

遍历二级索引树找到对应的主键后,再从索引组织表中查找数据所在的叶节点叫做「回表」。在英文中没有特定的词表示这个过程,叫做 table access by index rowidi...

May 14, 2023 71 words 1 min

covering index

即可以直接通过遍历聚簇索引获取到非主键列数据的场景,即不需要「回表(Table access by index rowid)」操作。覆盖索引一般出现在「联合索引」中,因...

May 14, 2023 98 words 1 min

Vanilla Emacs with Purcell

Introduction Emacs outshines all other editing software in approximately the same way that the noonday sun does the stars. It is not just bigger and brighter; it simply makes everything else vanish. – Neal Stephenson, In the Beginning was the Command Line (1998) Install Emacs-plus With Homebrew brew tap d12frosted/emacs-plus brew install emacs-plus --with-native-comp --with-modern-vscode-icon ln -s /usr/local/opt/emacs-plus@29/ /Applications Build Emacs on UbuntuLucius’s Workflow git clone git:// sudo apt install...

February 28, 2023 12640 words 26 min

The Left-Prefix Index Rule is determined by the B+tree structure

联合索引遵循「最左匹配原则」,MySQL 联合索引创建的时候会对 (a, b) 其中的 a 先进行排序,再在 a 的基础上对 b 进行排序。如果是 (a, b, c) 也是一样的方式...

February 10, 2023 428 words 1 min

The difference between B-tree and B+tree

B-Tree B+Tree All internal nodes and leaf nodes contain data pointers along with keys. Only leaf nodes contain data pointers along with keys, internal nodes contain keys only. There are no duplicate keys. Duplicate keys are present in this, all internal nodes are also present at leaves. Leaf nodes are not linked to each other. Leaf nodes are linked to each other. Sequential access of nodes is not possible. All...

February 10, 2023 385 words 1 min