btree | persistent B+Tree ( clustered index | Hashing library
kandi X-RAY | btree Summary
kandi X-RAY | btree Summary
This project is ongoing and is considered a work-in-progress for educational purposes. A persistent B+Tree implementation, designed as an index for a key value store, inspired by SQLite.
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Trending Discussions on btree
QUESTION
I have a table with contact details “lead” and another table with information about emails which have been sent to the leads “mail_log”
I want to get all leads which have received mail_id = 1 but not mail_id = 2. And the lead should not be deleted = 1. And the timestamp of mail_id 1 sould be more then one week ago
As result I need the email address of the lead and the date when the last mail was sent (in this case mail_id 1)
Thank you
...ANSWER
Answered 2022-Mar-14 at 21:32select l.email,
ml.timestamp
from lead l
join mail_log ml on l.id = ml.lead_id
where l.deleted <> 1
and ml.mail_id = 1
and ml.timestamp < DATEADD(day, -7, CAST(GETDATE() AS date))
QUESTION
I created an index as follows:
...ANSWER
Answered 2022-Mar-08 at 14:33I'm afraid the only thing to do is to remove the index
Don't be afraid, You can do it without any downtime :
- first create your new index in the good order, but with
CONCURRENTLY
to avoid any lock, - then, drop the old index.
No lock, and no query without index, with the only downside of having a 2n index size while you do the change.
QUESTION
I am using MySQL 8.0 and there is a slow query on a large table to be optimized.
The table contains 11 million rows of data and it's structure:
...ANSWER
Answered 2022-Feb-21 at 05:15I was able to eliminate the Using temporary
by adding an expression index:
QUESTION
I have the following 2 query plans for a particular query (second one was obtained by turning seqscan off):
The cost estimate for the second plan is lower than that for the first, however, pg only chooses the second plan if forced to do so (by turning seqscan off).
What could be causing this behaviour?
EDIT: Updating the question with information requested in a comment:
Output for EXPLAIN (ANALYZE, BUFFERS, VERBOSE)
for query 1 (seqscan on; does not use index). Also viewable at https://explain.depesz.com/s/cGLY:
ANSWER
Answered 2022-Feb-17 at 11:43You should have those two indexes to speed up your query :
QUESTION
I am trying to use a BTreeSet<(String, String, String)>
as a way to create a simple in-memory 'triple store'.
To be precise:
...ANSWER
Answered 2022-Jan-17 at 09:59I'd like to be able to build range-queries for all of the following:
QUESTION
I have worked my way around many challenges with MySQL, and i think right now i am able to build everything that i need, to get something to work. But now, for a pretty huge SQL statement that returns a lot of data, i need to work on MySQL performance for the first time.
I was hoping someone here could help me find out why the following statement is so incredibly slow. It takes over 3 minutes to collect 740 results out of different tables. The biggest table beeing the "reports" table, consisting of somewhere over 20.000 entries at the moment.
I can also educate myself if someone could just point me in the right direction. I don't even know where to search for answers for my current problem.
Okay, so here is the statement that i am talking about. Maybe, if someone has enough experience with SQL performance, something just right away jumps at them. I would be happy for any kind of feedback. I'll elaborate on the statement right after the code itself:
...ANSWER
Answered 2022-Jan-13 at 01:03Let's start by adding an index for each of the foreign keys used in your query -
QUESTION
I want to be able to specify an element and the tree and the function should give me a list of directions and if the element is not contained it should not return an error but rather a "Nothing" made by Maybe.
...ANSWER
Answered 2022-Jan-12 at 16:15The reason Just (L : getPath y lt)
does not work is because getPath y lt
is a Maybe [Direction]
, not a [Direction]
, hence it is not a list, and you thus can not prepend this with L
or R
.
You can make use of fmap :: Functor f => (a -> b) -> f a -> f b
to perform a mapping on the item wrapped in the Just
data constructor, and fmap f Nothing
will return Nothing
.
You thus can implement this as:
QUESTION
I'm trying to capture SQL DDL "CREATE" from a PostgreSQL schema dump that looks like this:
...ANSWER
Answered 2022-Jan-07 at 10:28sed
would be better tool for this:
QUESTION
I created a binary search tree and tried to print the binary search tree with this instance
...ANSWER
Answered 2022-Jan-01 at 16:17I found my answer myself. I created one function that shows like that. Here is the code
QUESTION
I'm just wondering how flexible OCaml's polymorphic variants are.
I know I can use the same constructor across different types but what is meant by the same constructor?
I know its fine to use `Nil here.
...ANSWER
Answered 2021-Dec-13 at 05:18You can have the vlist
and btree
definitions simultaneously. Values built from polymorphic variants are typed according to their structure, so there is no conflict between different uses of the same constructors.
Here is a session showing some possibilities that I tried:
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