Posts (page 82)
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4 min readTo update data between two tables in PostgreSQL, you can use the UPDATE command with a JOIN clause. This allows you to update records in one table based on matches with another table. First, you need to specify the two tables you want to update from and join them using a common column. Then, you can set the columns and values you want to update in the target table using the SET keyword. Finally, you can add a WHERE clause to specify the conditions for the update.
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5 min readTo draw a GIF on a canvas, you will first need to load the GIF image file onto the canvas using HTML and JavaScript. You can do this by creating a new Image object in JavaScript and setting its src attribute to the path of the GIF file.Once the GIF is loaded onto the canvas, you can use the canvas's drawImage() method to draw the GIF onto the canvas.
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7 min readTo create a role with superuser privileges in PostgreSQL, you can use the CREATE ROLE command with the SUPERUSER attribute. This command allows you to define a new role with the ability to perform any action within the database system, including altering and dropping other roles, modifying system catalogs, and running queries on all schemas and tables.When creating a role, you can specify the SUPERUSER attribute by including the keyword SUPERUSER in the command followed by the role name.
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8 min readTo share textures between a 2D canvas and a WebGL canvas, you can create a texture in WebGL, draw the content of the 2D canvas onto that texture, and then use the texture in the WebGL context.First, you need to create a texture object in WebGL by using the createTexture method. Next, you can bind the texture object with the bindTexture method. Then, you can use the texImage2D method to upload the content of the 2D canvas onto the WebGL texture.
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8 min readTo parse CSV in TypeORM and PostgreSQL, you can follow these steps: Use a library like csv-parser or fast-csv to read the CSV file and parse its contents. Create a connection to your PostgreSQL database using TypeORM. For each row in the CSV file, create a new entity instance using TypeORM and save it to the database. Make sure to handle any necessary data conversions or validations before saving the entity. Close the connection to the database once all entities have been saved.
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4 min readWhen translating a canvas to make it responsive, it is important to consider the dimensions and scaling of the canvas. One approach is to use CSS media queries to adjust the size of the canvas based on the screen size. This involves setting the width and height properties of the canvas element to a percentage of the viewport width and height.Another approach is to use JavaScript to dynamically adjust the size of the canvas based on the screen size.
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5 min readTo make the session always active in PostgreSQL, you can increase the idle session timeout value in the PostgreSQL server configuration file. By default, the idle session timeout value is set to 0, which means that sessions will not be closed due to inactivity. You can modify this value to a higher number to keep sessions active for a longer period of time. Additionally, you can use tools like PgBouncer to manage database connections and keep sessions active even during periods of inactivity.
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6 min readTo make a video preview with canvas, you will need to first load the video element onto the webpage. Then, create a canvas element where you will draw the video frames onto. Use JavaScript to capture the video frames in a loop and draw them onto the canvas using the drawImage() method.You can control the playback speed and quality of the video preview by adjusting the frame rate and dimensions of the canvas.
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7 min readTo restore a PostgreSQL database in a Docker Compose environment, you can follow these steps:Stop the Docker Compose services that are using the PostgreSQL database to ensure that no changes are being made while restoring the database. Remove the volume associated with the PostgreSQL container to reset the database to its initial state. You can do this by running the command "docker-compose down -v" to stop and remove the Docker containers and volumes.
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7 min readTo display a JavaScript object with canvas, you can first create a canvas element in your HTML document. Next, you can use JavaScript code to access the canvas context and draw the object on the canvas by specifying its properties such as position, size, color, and shape. You can use methods like fillRect, strokeRect, or arc to draw shapes. You can also iterate over the object properties and draw each one individually if the object is complex.
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5 min readTo unnest a single quoted JSON array in PostgreSQL, you can use the JSON functions provided by PostgreSQL. You can start by using the json_parse_text function to convert the single quoted JSON array into a valid JSON format. Then, you can use the json_array_elements function to unnest the JSON array and get the individual elements as rows in the result set. This way, you can easily work with the data stored in the JSON array and perform any necessary operations on it.
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5 min readTo draw multiple images to a single canvas, you can use the HTML5 canvas element along with JavaScript.First, you need to create a canvas element in your HTML file and give it an id so you can reference it in your JavaScript code.Next, create an Image object for each image you want to draw and set the src attribute to the file path of the image.After that, use the canvas.getContext('2d') method to get the 2D rendering context of the canvas.