A degenerate bilinear form is a type of bilinear form in linear algebra with a specific property: it does not have full rank.
The "degree of anonymity" generally refers to the extent to which an individual's identity is concealed or protected while engaging in activities, particularly in online environments. It can be understood in several contexts: 1. **Online Activities**: In the digital space, the degree of anonymity can vary based on the methods and tools used for online interactions. Some platforms may allow users to operate under pseudonyms, while others may require real identities. Technologies like VPNs, Tor, and encryption can enhance anonymity.
DeLorme is a company known for its mapping and GPS technology products. Founded in 1976 by David DeLorme, the company initially gained recognition for its topographic map books and atlases, which were used by outdoor enthusiasts, hikers, and those needing detailed geographic information. In the 1990s, DeLorme expanded into the digital mapping and GPS space, creating software products like Topo USA, which provides users with detailed topographic maps and navigation capabilities.
PostgreSQL feels good.
Its feature set is insanely large! Just look at stuff like: stackoverflow.com/questions/1986491/sql-split-string-by-space-into-table-in-postgresql/1993058#1993058
If Oracle is the Microsoft of database, Postgres is the Linux, and MySQL (or more precisely MariaDB) is the FreeBSD (i.e. the one that got delayed by legal issues). Except that their software licenses were accidentally swapped.
The only problem with Postgres is its name. PostgreSQL is so unpronounceable and so untypeable that you should just call it "Postgres" like everyone else.
On Ubuntu 20.10 PostgreSQL 12.6, login with
psql on my default username without sudo fails with: stackoverflow.com/questions/11919391/postgresql-error-fatal-role-username-does-not-existThis is the one that worked on Ubuntu 21.04: stackoverflow.com/questions/11919391/postgresql-error-fatal-role-username-does-not-exist/38444152#38444152Explanation:
sudo -u postgres createuser -s $(whoami)
createdb $(whoami)You can now run shows that peer authentication is available to all users apparently:
psql without any password. This works without password due to peer authentication:sudo cat /etc/postgresql/12/main/pg_hba.conflocal all postgres peer
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all peerList users:output:
psql -c '\du' List of roles
Role name | Attributes | Member of
-------------+------------------------------------------------------------+-----------
ciro | Superuser, Create role, Create DB | {}
owning_user | | {}
postgres | Superuser, Create role, Create DB, Replication, Bypass RLS | {}Delete user later on:
psql -c 'DROP USER username;'Help toplevel:
helpList supported SQL commands:
\hShow syntax for one type of command:
\h SELECTList all databases:which shows:
psql -c '\l' Name | Owner | Encoding | Collate | Ctype | Access privileges
-------------+----------+----------+-------------+-------------+-----------------------
ciro | postgres | UTF8 | en_GB.UTF-8 | en_GB.UTF-8 |
postgres | postgres | UTF8 | en_GB.UTF-8 | en_GB.UTF-8 |
template0 | postgres | UTF8 | en_GB.UTF-8 | en_GB.UTF-8 | =c/postgres +
| | | | | postgres=CTc/postgres
template1 | postgres | UTF8 | en_GB.UTF-8 | en_GB.UTF-8 | =c/postgres +
| | | | | postgres=CTc/postgres
testdb0 | postgres | UTF8 | en_GB.UTF-8 | en_GB.UTF-8 |
(6 rows)If you didn't give a database from the command line e.g.:you can do that afterwards with:
psql\c testdb0Let's create a table and test that it is working:
psql testdb0 -c 'CREATE TABLE table0 (int0 INT, char0 CHAR(16));'List tables, no special tables:gives:
psql testdb0 -c '\dt' List of relations
Schema | Name | Type | Owner
--------+--------+-------+-------
public | table0 | table | ciro
(1 row)View table schema: stackoverflow.com/questions/109325/postgresql-describe-tableoutput:
psql testdb0 -c '\d+ table0' Table "public.table0"
Column | Type | Collation | Nullable | Default | Storage | Stats target | Description
--------+---------------+-----------+----------+---------+----------+--------------+-------------
int0 | integer | | | | plain | |
char0 | character(16) | | | | extended | |Insert some data into it and get the data out:output:
psql testdb0 -c "INSERT INTO table0 (int0, char0) VALUES (2, 'two'), (3, 'three'), (5, 'five'), (7, 'seven');"
psql testdb0 -c 'SELECT * FROM table0;' int0 | char0
------+------------------
2 | two
3 | three
5 | five
7 | seven
(4 rows)Delete the table:
psql testdb0 -c 'DROP TABLE table0;'Ubuntu 21.10 has a certain default level of logging by default to:but it does not log everything, only/mostly errors it seems.
/var/log/postgresql/postgresql-13-main.logSetting:under:and then restarting the server:just works.
log_statement = 'all'/etc/postgresql/13/main/postgresql.confsudo service restart postgresqlRealtime monitoring for long queries instead: stackoverflow.com/questions/8597516/app-to-monitor-postgresql-queries-in-real-time
When using SQL REPEATABLE READ isolation level and SQL SERIALIZABLE isolation level, concurrent transactions may fail with a serialization failure, and then you might need to retry them. You server code or your ORM must always account for that.
Related questions:
- stackoverflow.com/questions/7705273/what-are-the-conditions-for-encountering-a-serialization-failure
- stackoverflow.com/questions/59351109/error-could-not-serialize-access-due-to-concurrent-update
- stackoverflow.com/questions/50797097/postgres-could-not-serialize-access-due-to-concurrent-update/51932824
The minimalism, serverlessness/lack of temporary caches/lack of permission management, Hipp's religious obsession with efficiency, the use of their own pure Fossil version control[ref]. Wait, scrap that last one. Pure beauty!
Official Git mirror: github.com/sqlite/sqlite
Create a table
sqlite3 db.sqlite3 "
CREATE TABLE 'IntegerNames' (int0 INT, char0 CHAR(16));
INSERT INTO 'IntegerNames' (int0, char0) VALUES (2, 'two'), (3, 'three'), (5, 'five'), (7, 'seven');
"List tables:output:
sqlite3 db.sqlite3 '.tables'IntegerNamesShow schema of a table:outputs the query that would generate that table:
sqlite3 db.sqlite3 '.schema IntegerNames'CREATE TABLE IF NOT EXISTS 'IntegerNames' (int0 INT, char0 CHAR(16));Example: sqlite/ip.c, adapted from www.sqlite.org/loadext.html, also mentioned explained at: stackoverflow.com/questions/7638238/sqlite-ip-address-storage/76520885#76520885.
Sample usage in the test program: sqlite/test.sh.
The default isolation level for SQLite is SERIALIZABLE
It does not appear possible to achieve the other two levels besides SERIALIZABLE and READ UNCOMMITED
Includes its own copy of sqlite3, you don't use the system one, which is good to ensure compatibility. The version is shown at: github.com/mapbox/node-sqlite3/blob/918052b538b0effe6c4a44c74a16b2749c08a0d2/deps/common-sqlite.gypi#L3 SQLite source is tracked compressed in-tree: github.com/mapbox/node-sqlite3/blob/918052b538b0effe6c4a44c74a16b2749c08a0d2/deps/sqlite-autoconf-3360000.tar.gz horrendous. This explains why it takes forever to clone that repository. People who don't believe in git submodules, there's even an official Git mirror at: github.com/sqlite/sqlite
It appears to spawn its own threads via its C extension (since JavaScript is single threaded and and SQLite is not server-based), which allows for parallel queries using multiple threads: github.com/mapbox/node-sqlite3/blob/v5.0.2/src/threading.h
Hello world example: nodejs/node-sqlite3/index.js.
As of 2021, this had slumped back a bit, as maintainers got tired. Unmerged pull requests started piling more, and
better-sqlite3 Node.js package started pulling ahead a little.- github.com/mapbox/node-sqlite3/issues/1381
FATAL ERROR: Error::ThrowAsJavaScriptException napi_throwwith Node.jsworker_threadsvsbetter-sqlite3Node.js package github.com/JoshuaWise/better-sqlite3/issues/237
Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 3. Visual Studio Code extension installation.
Figure 4. Visual Studio Code extension tree navigation.
Figure 5. Web editor. You can also edit articles on the Web editor without installing anything locally.Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.Video 4. OurBigBook Visual Studio Code extension editing and navigation demo. Source. 
- Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact