PostgreSQL worst practices, version PGConf.US 2017 by Ilya Kosmodemiansky
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Transcript of PostgreSQL worst practices, version PGConf.US 2017 by Ilya Kosmodemiansky
Best practices are just boring
• Never follow them, try worst practices• Only worst practices can really help you screw things up in amost effective way
• PostgreSQL consultants are nice people - keep them happy!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
How it works?
• I have a list, a little bit more than 100 worst practices• I do not make this stuff up, all of them are real-life examples• I reshuffle my list every time before presenting and pick a fewexamples
• Well, there are some things, which I like more or less, so it isnot a very honest shuffle
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
0. Do not use indexes (a test one!)
• Basically, there is no difference between full table scan andindex scan
• You can check that. Just insert 10 rows into a test table onyour test server and compare.
• Nobody deals with more than 10 row tables in production!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
1. Use as many count(*) as you can
• Figure 301083021830123921 is very informative for the enduser
• If it changes in a second to 30108302894839434020, it is stillinformative
• select count(*) from sometable is a quite light-weighted query• Tuple estimation from pg_catalog can never be preciseenough to you
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
2. Use ORM
• All databases share the same syntax• You must write database-independent code• Are there any benefits, which are based on database specificfeatures?
• It always good to learn a new complicated technology
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
3. Move joins to your application
• Just select * a couple of tables into the application written inyour favorite programming language
• Than join them at the application level
• Now you only need to implement nested loop join, hash joinand merge join as well as query optimizer and page cache
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
3. Move joins to your application
• Just select * a couple of tables into the application written inyour favorite programming language
• Than join them at the application level• Now you only need to implement nested loop join, hash joinand merge join as well as query optimizer and page cache
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
4. Be in trend, be schema-less
• You do not need to design the schema• You only need one table, two columns: id bigserial and extrajsonb
• JSONB datatype is pretty effective in PostgreSQL, you canquery it just like a well-structured table
• Even if you put a 100M of JSON in it• Even if you have 1000+ tps
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
5. Be agile, use EAV
• You only need 3 tables: entity, attribute, value
• At some point add the 4th: attribute_type• When it starts slowing down, just call those four tables TheCore and add 1000+ tables with denormalized data
• If it is not enough, you can always add value_version
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
5. Be agile, use EAV
• You only need 3 tables: entity, attribute, value• At some point add the 4th: attribute_type
• When it starts slowing down, just call those four tables TheCore and add 1000+ tables with denormalized data
• If it is not enough, you can always add value_version
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
5. Be agile, use EAV
• You only need 3 tables: entity, attribute, value• At some point add the 4th: attribute_type• When it starts slowing down, just call those four tables TheCore and add 1000+ tables with denormalized data
• If it is not enough, you can always add value_version
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
5. Be agile, use EAV
• You only need 3 tables: entity, attribute, value• At some point add the 4th: attribute_type• When it starts slowing down, just call those four tables TheCore and add 1000+ tables with denormalized data
• If it is not enough, you can always add value_version
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
6. Try to create as many indexes as you can
• Indexes consume no disk space• Indexes consume no shared_bufers• There is no overhead on DML if one and every column in atable covered with bunch of indexes
• Optimizer will definitely choose your index once you created it• Keep calm and create more indexes
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
7. Always keep all your time series data
• Time series data like tables with logs or session history shouldnever be deleted, aggregated or archived, you always need tokeep it all
• You will always know where to check, if you run out of diskspace
• You can always call that Big Data• Solve the problem using partitioning... one partition for anhour or for a minute
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
7. Always keep all your time series data
• Time series data like tables with logs or session history shouldnever be deleted, aggregated or archived, you always need tokeep it all
• You will always know where to check, if you run out of diskspace
• You can always call that Big Data• Solve the problem using partitioning... one partition for anhour or for a minute
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
7. Always keep all your time series data
• Time series data like tables with logs or session history shouldnever be deleted, aggregated or archived, you always need tokeep it all
• You will always know where to check, if you run out of diskspace
• You can always call that Big Data
• Solve the problem using partitioning... one partition for anhour or for a minute
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
7. Always keep all your time series data
• Time series data like tables with logs or session history shouldnever be deleted, aggregated or archived, you always need tokeep it all
• You will always know where to check, if you run out of diskspace
• You can always call that Big Data• Solve the problem using partitioning... one partition for anhour or for a minute
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
8. Turn autovacuum off
• It is quite auxiliary process, you can easily stop it• There is no problem at all to have 100Gb data in a databasewhich is 1Tb in size
• 2-3Tb RAM servers are cheap, IO is a fastest thing in moderncomputing
• Besides, everyone likes BigData
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
9. Reinvent Slony
• If you need some data replication to another database, try toimplement it from scratch
• That allows you to run into all sorts of problems PostgreSQLhad since introducing Slony
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
9. Reinvent Slony
• If you need some data replication to another database, try toimplement it from scratch
• That allows you to run into all sorts of problems PostgreSQLhad since introducing Slony
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
10. Keep master and slave on different hardware
• That will maximize the possibility of unsuccessful failover
• To make things even worse, you can change only slave-relatedparameters at slave, leaving defaults for shared_buffers etc.
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
10. Keep master and slave on different hardware
• That will maximize the possibility of unsuccessful failover• To make things even worse, you can change only slave-relatedparameters at slave, leaving defaults for shared_buffers etc.
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
11. Put a synchronous replica to remote DC
• Indeed! That will maximize availability!
• Especially, if you put the replica to another continent
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
11. Put a synchronous replica to remote DC
• Indeed! That will maximize availability!• Especially, if you put the replica to another continent
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
12. Never use Foreign Keys
• Consistency control at application level always works asexpected
• You will never get data inconsistency without constraints• Even if you already have a bullet proof framework to maintainconsistency, could it be good enough reason to use it?
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
13. Always use text type for all columns
• It is always fun to reimplement date or ip validation in yourcode
• You will never mistakenly convert ”12-31-2015 03:01AM” to”15:01 12 of undef 2015” using text fields
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
14. Always use improved ”PostgreSQL”
• Postgres is not a perfect database and you are smart• All that annoying MVCC staff, 32 bit xid and autovacuumnightmares look the way they do because hackers are oldschooland lazy
• Hack it in a hard way, do not bother submitting your patch tothe community, just put it into production
• It is easy to maintain such production and keep it compatiblewith ”not perfect” PostgreSQL upcoming versions
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
15. Postgres likes long transactions
• Always call external services from stored procedures (likesending emails)
• Oh, it is arguable... It can be, if 100% of developers werefamiliar with word timeout
• Anyway, you can just start transaction and go away for aweekend
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
15. Postgres likes long transactions
• Always call external services from stored procedures (likesending emails)
• Oh, it is arguable... It can be, if 100% of developers werefamiliar with word timeout
• Anyway, you can just start transaction and go away for aweekend
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
15. Postgres likes long transactions
• Always call external services from stored procedures (likesending emails)
• Oh, it is arguable... It can be, if 100% of developers werefamiliar with word timeout
• Anyway, you can just start transaction and go away for aweekend
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
16. Never read your code, write it!
genre_id IN( SELECT id FROM genres WHERE genres.id IN
(SELECT * FROM unnest(array[155])))
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
17. Have problems with you PostgreSQL installation?
• Move those problems to the container!
• It is always good to have something very stable insidesomething very unstable!
• Now your problems are both inside and outside!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
17. Have problems with you PostgreSQL installation?
• Move those problems to the container!• It is always good to have something very stable insidesomething very unstable!
• Now your problems are both inside and outside!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
17. Have problems with you PostgreSQL installation?
• Move those problems to the container!• It is always good to have something very stable insidesomething very unstable!
• Now your problems are both inside and outside!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
17. Not only Slony should be reinvented!
• Need to convert timestamp? Stored procedure in C will help!
• Need a message queue? Write it!• Won’t use ORM? Write your own in plpgsql
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
17. Not only Slony should be reinvented!
• Need to convert timestamp? Stored procedure in C will help!• Need a message queue? Write it!
• Won’t use ORM? Write your own in plpgsql
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
17. Not only Slony should be reinvented!
• Need to convert timestamp? Stored procedure in C will help!• Need a message queue? Write it!• Won’t use ORM? Write your own in plpgsql
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
18. And never, never use exceptions
• Documentation says they are slow
• Raise notice on errors - everyone reads logs constantly!• Who cares about errors?
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
18. And never, never use exceptions
• Documentation says they are slow• Raise notice on errors - everyone reads logs constantly!
• Who cares about errors?
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
18. And never, never use exceptions
• Documentation says they are slow• Raise notice on errors - everyone reads logs constantly!• Who cares about errors?
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
19. Application runs out of connections?
• Set max_connections to 1000
• Common, servers with 1000 CPUs are cheap now• Who said PostgreSQL workers have some overhead?• And never ever use pgbouncer!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
19. Application runs out of connections?
• Set max_connections to 1000• Common, servers with 1000 CPUs are cheap now
• Who said PostgreSQL workers have some overhead?• And never ever use pgbouncer!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
19. Application runs out of connections?
• Set max_connections to 1000• Common, servers with 1000 CPUs are cheap now• Who said PostgreSQL workers have some overhead?
• And never ever use pgbouncer!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
19. Application runs out of connections?
• Set max_connections to 1000• Common, servers with 1000 CPUs are cheap now• Who said PostgreSQL workers have some overhead?• And never ever use pgbouncer!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
20. Use pgpool-II instead
• Pooling connections with pgpool is easy...
• Just like writing a code in that Emacs OS...• Simple config, useful features• Consulters are happy!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
20. Use pgpool-II instead
• Pooling connections with pgpool is easy...• Just like writing a code in that Emacs OS...
• Simple config, useful features• Consulters are happy!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
20. Use pgpool-II instead
• Pooling connections with pgpool is easy...• Just like writing a code in that Emacs OS...• Simple config, useful features
• Consulters are happy!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
20. Use pgpool-II instead
• Pooling connections with pgpool is easy...• Just like writing a code in that Emacs OS...• Simple config, useful features• Consulters are happy!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
21. Always start tuning PostgreSQL...
• From optimizer options in postgresql.conf
• Forget about those shared_buffers and checkpoints!• geqo options are a good candidate to be a silver bullet!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
21. Always start tuning PostgreSQL...
• From optimizer options in postgresql.conf• Forget about those shared_buffers and checkpoints!
• geqo options are a good candidate to be a silver bullet!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
21. Always start tuning PostgreSQL...
• From optimizer options in postgresql.conf• Forget about those shared_buffers and checkpoints!• geqo options are a good candidate to be a silver bullet!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
22. Have heard about a cool new feature?
• Use it in production immediately!
• Attend MVCC Unmasked by Bruce Momjian (Today, 15:50,Liberty I)
• Learn about xmin and xmax• Use it in your applications logic!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
22. Have heard about a cool new feature?
• Use it in production immediately!• Attend MVCC Unmasked by Bruce Momjian (Today, 15:50,Liberty I)
• Learn about xmin and xmax• Use it in your applications logic!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
22. Have heard about a cool new feature?
• Use it in production immediately!• Attend MVCC Unmasked by Bruce Momjian (Today, 15:50,Liberty I)
• Learn about xmin and xmax
• Use it in your applications logic!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
22. Have heard about a cool new feature?
• Use it in production immediately!• Attend MVCC Unmasked by Bruce Momjian (Today, 15:50,Liberty I)
• Learn about xmin and xmax• Use it in your applications logic!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
Do not forget
That was WORST practices talk
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
Send me your favourite!
dataegret.com
Why this talk
• Linux is a most common OS for databases
• DBAs often run into IO problems
• Most of the information on topic is written by kerneldevelopers(for kernel developers) or is checklist-style
• Checklists are useful, but up to certain workload
dataegret.com
