duck_db | simple b+tree RDMS ( use c | Database library
kandi X-RAY | duck_db Summary
kandi X-RAY | duck_db Summary
c/c++ build a simple b+tree RDMS (use c/c++ to develop a small relational database based on B+tree)
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Community Discussions
Trending Discussions on Database
QUESTION
I want to be able to (at run time) create or alter a DB schema dynamically on a particular event (e.g. click of a button) using FormHandler microservice of Gramex.
...ANSWER
Answered 2022-Apr-08 at 06:20You can do it using queryfunction of FormHandler which can modify the query based on the query parameters passed in the url.
Refer the link below for more https://gramener.com/gramex/guide/formhandler/#formhandler-queryfunction
QUESTION
I am getting the following error while trying to upload a dataset to Hub (dataset format for AI) S3SetError: Connection was closed before we received a valid response from endpoint URL: "<...>".
So, I tried to delete the dataset and it is throwing this error below.
CorruptedMetaError: 'boxes/tensor_meta.json' and 'boxes/chunks_index/unsharded' have a record of different numbers of samples. Got 0 and 6103 respectively.
Using Hub version: v2.3.1
...ANSWER
Answered 2022-Mar-24 at 01:06Seems like when you were uploading the dataset the runtime got interrupted which led to the corruption of the data you were trying to upload. Using force=True
while deleting should allow you to delete it.
For more information feel free to check out the Hub API basics docs for details on how to delete datasets in Hub.
If you stop uploading a Hub dataset midway through your dataset will be only partially uploaded to Hub. So, you will need to restart the upload. If you would like to re-create the dataset, you can use the overwrite = True
flag in hub.empty(overwrite = True)
. If you are making updates to an existing dataset, you should use version control to checkpoint the states that are in good shape.
QUESTION
I ran into an issue that I haven't found a solution to yet. I have a collection with dozens of documents that every one of the documents contains a list (let's use the name 'list' as a key for that list) with ids of other documents(they are connected in some way).
some of the documents in the collection were deleted and I try to find all the documents that contain the ids of documents that do not exist anymore in the collection.
example:
As to the example above: I want to get the document with the id : 5e3266e9bd724a000107a902 because it contains a list with the id 5e32a7f7bd724a00012c1104 that does not exist anymore.
...ANSWER
Answered 2022-Mar-02 at 03:10Here is a solution that works exploiting $lookup
on the same collection (think "self-JOIN"):
QUESTION
Given a connection to the PostgreSQL database for user 'Alice', is there a statement that could be executed to switch to user 'Bob'?
Motivation: Looking to avoid having separate pools for each user (i.e. re-use a connection that was previously used by another user).
...ANSWER
Answered 2022-Mar-01 at 22:09In PgAdmin open part Login/Group roles. Right click and in opened window enter new user, set permission and defined password. After refresh you will see e.g. Alice in Login/Group roles. After that open database with logged user. Click on something like mondial/postgres@PostgresSQL (db/user@server) and choose new connection. Chose which db wish to use and user wich will be connected on db.
After that you will have mondial/Alice@PostgresSQL
QUESTION
ANSWER
Answered 2022-Feb-28 at 12:43The problem consist from creating connection in separate file (must be create in App).
QUESTION
As the title suggests I'm wondering how to create an effective index for GROUP BY queries in CosmosDB.
Say the documents look something like:
...ANSWER
Answered 2021-Sep-27 at 20:51Currently GROUP BY does not not yet use the index.
This is currently being worked on. I would revisit sometime towards the end of the year to verify it is supported.
QUESTION
i have a database field that is set to decimal, while in my Go project i am having problem choosing which datatype can be use. each time i send a create reuquest to my code, i get a "cannot marshal 'decimal' into #golang datatype#
this my database schema
...ANSWER
Answered 2022-Feb-15 at 12:13If you look into documentation for Gocql package, then you will see that the decimal
is mapped to the Go's infDec
data type (see its doc) so you need to use it instead of Float64
.
QUESTION
I want to copy one big database table to another. This is my current approach:
...ANSWER
Answered 2022-Jan-20 at 12:45You can also "copy on database level" from within ABAP SQL using a combined INSERT
and SELECT
:
QUESTION
- Hi, we are trying to upgrade 2.0.202 from 1.4.200. We are getting an error related to running our tests. While persisting data we are getting below error. Any suggestions?
Caused by: org.h2.jdbc.JdbcSQLIntegrityConstraintViolationException: NULL not allowed for column "***"; SQL statement:
...ANSWER
Answered 2022-Jan-31 at 01:05You cannot use H2 2.0.202 with Hibernate ORM 5.6, because H2Dialect
in Hibernate ORM produces invalid SQL for H2, H2 2.x is more restrictive and doesn't accept it by default.
H2 2.0.204 and later versions (current version is 2.1.210) have a LEGACY
compatibility mode, it can be enabled by appending ;MODE=LEGACY
to JDBC URL. This mode provides some limited compatibility with old versions of H2.
This trick shouldn't be required for Hibernate ORM 6.0 when it will be released.
Edited
Changes for H2 2.x.y were backported to Hibernate ORM 5.6.5.
QUESTION
I am confused in choosing database service for my flutter application. I started using firebase but as it is based on NoSQL , But if i am getting the need for rows and columns for my data which backend service should i use!.
...ANSWER
Answered 2022-Jan-23 at 23:20I think it depends on how you want to access the data. If you're wanting to stream and push notifications, I would stick with Firebase. If you just need to get and post data, focus more on api implementation. With a solid rest api, you can change up your database/backend all you want and just have to update the api, not your app.
I, personally, suggest searching around for data modeling techniques in Firebase. Check out the Fireship channel on youtube. In his channel's videos, search for modeling
and you'll find a ton of info on Firebase data modeling. Many will reference Angular, but the techniques are the same.
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
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Install duck_db
输入make进行编译,输入./duck_db即可运行;
make clean清除文件。
数据库二进制文件存的目录:./data/db.bin
使用C/C++开发;
已实现基本的CURD操作,使用控制台SQL: 新建记录(create),操作SQL:insert db {index} {name} {age} {email}; 更新记录(update),操作语句:update db {name} {age} {email} where id={index}; 单条读取记录(read),操作语句:select * from db where id={index}; 范围读取(read in range),操作语句:select * from db where id in({minIndex},{maxIndex}); 删除记录(delete),操作语句:delete from db where id ={index};
底层使用B+树(B+ TREE)构建索引;
利用二进制存储数据表;
暂不支持自定义表结构,数据库表结构固定为:id,name,age,email,如图:
创建一个控制台对话交互程序(REPL:read-execute-print loop);
创建一个简单的词法分析器用来解析SQL语句;
编写CURD函数实现数据库的增删改查操作;
创建一个b+树索引引擎,进行数据库的索引和磁盘读写操作,数据表将以二进制的形式存储。
根节点至少有两个子节点;
每个节点有M-1个key,并且以升序排列;
位于M-1和M key的子节点的值位于M-1 和M key对应的Value之间;
其它节点至少有M/2个子节点;
有k个子结点的结点必然有k个关键码;
非叶结点仅具有索引作用,跟记录有关的信息均存放在叶结点中。
树的所有叶结点构成一个有序链表,可以按照关键码排序的次序遍历全部记录。
由于B+树在内部节点上不包含数据信息,因此在内存页中能够存放更多的key。 数据存放的更加紧密,具有更好的空间局部性。因此访问叶子节点上关联的数据也具有更好的缓存命中率。
B+树的叶子结点都是相链的,因此对整棵树的便利只需要一次线性遍历叶子结点即可。而且由于数据顺序排列并且相连,所以便于区间查找和搜索。而B树则需要进行每一层的递归遍历。相邻的元素可能在内存中不相邻,所以缓存命中性没有B+树好。
无法创建自定义表;
不支持事物处理,IO优化;
不支持远程登录数据库,只可以本地使用;
CURD高级功能如函数,约束,连表操作等不支持;
更多高级特性等。
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