What is the "N+1 selects problem" in ORM (Object-Relational Mapping)?

The "N+1 selects problem" is generally stated as a problem in Object-Relational mapping (ORM) discussions, and I understand that it has something to do with having to make a lot of database...

Prevent "n+1 selects" with JPA/Hibernate constructor expression?

I have two entities, Item and Data, and a DTO class ItemData. ItemData consists of Item and Data and has no JPA mapping. To retreive a list of populated ItemDatas, I use a constructor expression...

mongodb - perform batch query

I need query data from collection a first, then according to those data, query from collection b. Such as: For each id queried from a query data from b where "_id" == id In SQL, this can be...

JPQL Constructor Expressions, how to eagerly fetch the main entity in 'select new'

The original query I have is somewhat complex, but what I'm trying to do is obtain the entity AlertCondition plus some additional fields. + " SELECT new...

Hibernate creating N+1 queries for @ManyToOne JPA annotated property

I have these classes: @Entity public class Invoice implements Serializable { @Id @Basic(optional = false) private Integer number; private BigDecimal value; //Getters and...

python ParseError: Bad Input on line

ok so I a trying to make a calculator in python and it comes up with ParseError: Bad Input on line 7 and ParseError: Bad Input on line 6 etc. all the way down to ParseError: Bad Input on line 1,...

What does "Warning: mysqli_stmt_bind_param() expects parameter 1 to be mysqli_stmt, boolean given" mean?

This is my php and html code. <!--PHP --> <?php # Script 9.5 - register.php #2 // This script performs an INSERT query to add a record to the events table $page_title = 'Machinovate | Add...

Insert difficulties with SQLite database (for android)

I've some problems with my code. I need to develop an app with some info about shops. It's a one table database. Here are my 4 java files. `package com.example.rpata.roxyapp; public class...

JPA @OneToOne select lists with N+1 queries

I'm actually trying to use JPA @OneToOne annotation to link a Child entity to its Parent. It's working well, except the fact that when getting a list of Childs, the JPA engine (Hibernate in this...

Referencing a Worksheet: Application-defined or Object-defined error

I managed to get my code working except this part: ' colle data / année Windows(Namepatch3).Activate For j = 0 To (finas - debutas) Worksheets(1).Cells(2 + cpt, debutad + j) = Vcol(j) ...

OSX ld: library not found for -lssl

I am trying to install mysqlclient in virtrualenv on OSX high sierra, with python 3. And got the following error: Failed building wheel for mysqlclient Running setup.py clean for...

Failed building wheel for xmlsec - mac

I'm installing my mac on python virtualenv environment. Whenever I install requirement packages command "pip install -r requirements.txt" i got this messages. pip install -r requirements.txt...

themefiend Multiple product options add-on zoom (disable)

I'm using Themefiends multiple product options add-on for our Bigcartel shop. I want to disable the zoom option that comes with it - zoom of product pictures on hover. It also interferes with the...

Hibernate performs N+1 selects instead of 1 query when using the Query Cache

I'm stuck with a problem, I feel really lost and don't know what to do. I use query cache + second-level cache and I want to cache results for 10 seconds properly. So here is...

How to fix "Potential unnecessary eager load detected on `LogEntry.user`"

I'm creating a new Django 2.2 project with plugin nplusone(https://github.com/jmcarp/nplusone). When I try to go on /admin URL I get a next error “Potential unnecessary eager load detected on...

Meteor-files s3 upload: insert is not a function on client side

I'm trying to use ostrio:files aka Meteor-files with s3. When using the example s3 code running Images.insert on the CLIENT returns insert is not a function. My code is exact to example on the s3...

How to read data from dynamo db table into dataframe?

Below is the code where I am trying to read data from dynamo db and load it into a dataframe. Is it possible to do the same using scanamo? import org.apache.hadoop.io.Text; import...

Laravel - How to handle Undefined Offset: 1

I have a Laravel-5.8 project. I am using dynamic input field as shown below: StoreAppraisalGoalRequest class StoreAppraisalGoalRequest extends FormRequest { public function authorize() { ...

Laravel - How to validate fields from another tables in Request Rules

Using Laravel-5.8, I am trying to delevop a web application.I have two tables: goals and goal_details. Goal is the main model class. Using Rules and Request in Laravel: public function rules() { ...

GraphObject.make requires a class function or GoJS class name or name of an object builder, not: ToolTip

My version is gojs-1.7.22 and I am trying to load the sample productionProcess but its retrieving the following error: "GraphObject.make requires a class function or GoJS class name or name of an...

How to add information from the DB to an existing array of objects?

I have an array in the following format; // echo '<pre>' . var_export($this->viewableFields, true) . '</pre>'; array ( 0 => (object) array( 'formId' => '4', 'userId' => '7' ), ...

Detecting N+1 query issues during testing with JPA and Hibernate

We're using https://github.com/vladmihalcea/db-util which is a great tool, but we're facing a challenge regarding Session cache, that as mentioned in another question, it can't be disabled. So,...

Doctrine adds extra queries during hydration causing n+1 problem with "normal" one to one and self-referenced relations

News are related to each other using one-to-many self-referencing approach (one news is parent and can have many children). What's more each News has got normal (non self-referenced) one to one...

How to download file from Cloud Storage [Firebase Hosting]

I would like to make a web app using Firebase Hosting. make audio file using Cloud text to speech API upload that audio file to Cloud Storage download that audio file from Cloud Storage to a web...

How to avoid N + 1 queries with self-referential table in Rails

How to I correctly use includes to avoid N + 1 queries in this situation: I have a set of categories that can be nested (i.e., they form a tree). For example: Teaching Course 1 Office...

Is it possible to count the number of SQL queries with Flask / SQLAlchemy / Pytest / SQLite?

I have a Flask project which uses SQLAlchemy and a database. For testing, I replace the database by an SQLite database. Now I would like to run some of the views and test for the number of queries...

aws elastic beanstalk cannot create scaling trigger fails with AWSEBCloudwatchAlarmHigh null values not allowed

When I try to specify a scaling trigger it keeps erroring with Service:AmazonCloudFormation, Message:[/Resources/AWSEBCloudwatchAlarmHigh/Type/Dimensions/0/Value/Fn::GetAtt/0] 'null' values are...

D3 Sankey link scaling issue

I need to draw a sankey chart to show associations. I have scaled the nodes using d3.scaleLinear() to give meaning to small nodes as well but the links are not scaling as per nodes. I have tried...

Is there a better way to write this MS SQL Server query?

Hello and thank you for your time, I am new to SQL. Currently using MS SQL SERVER my question: Is there a better way to write this query? -- most important I am also not sure if I understand the...

Showing lineleft node on collapse

Hi I am using google visualization org chart to create org chart which is having SharPoint as source it work fine and but whenever collapse it show small left node and want to remove this extra...