Posts (page 119)
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4 min readTo implement a custom datatype in Hibernate, you need to create a custom UserType class that implements the org.hibernate.usertype.UserType interface. This UserType class should define the mapping between your custom datatype and the database column type.In the UserType implementation, you need to override methods such as nullSafeGet(), nullSafeSet(), and returnedClass().
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4 min readIn Hibernate, caching for many-to-one mapping works by storing multiple instances of a related entity in the cache for quicker access and retrieval. When a many-to-one relationship is established between two entities, Hibernate stores the related entity object in the cache based on the foreign key of the relationship.
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7 min readTo get the insert and delete count with Hibernate, you can use the Session interface methods getStatistics() and getSessionFactory().First, obtain the statistics of the session by calling getStatistics() on the Session object. Then, you can get the insert count and delete count by using the getEntityInsertCount() and getEntityDeleteCount() methods on the Statistics object.Alternatively, you can also access the insert and delete count using the StatisticsFactory interface.
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5 min readTo add values in a single column of multiple rows in PostgreSQL, you can use the UPDATE statement along with the SET clause to modify the values in the specified column. You can use various conditions to identify the rows that you want to update and then perform the addition operation on the values in the column. Additionally, you can also use functions like SUM() or aggregate functions to calculate the sum of values in the column across multiple rows.
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6 min readThere are several ways to migrate or copy PostgreSQL tables to Oracle using Python. One common approach is to use the SQLAlchemy library, which provides a way to connect to both PostgreSQL and Oracle databases.First, you would need to establish connections to both databases using SQLAlchemy. You can then query the PostgreSQL database for the data you want to migrate and insert it into the Oracle database using SQL statements.
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5 min readTo remove special characters from a string in PostgreSQL, you can use the regexp_replace function. This function allows you to replace a pattern in a string with a specified string. You can use a regular expression pattern to identify and replace special characters in a string. For example, to remove all special characters except alphanumeric characters from a string, you can use the following query: SELECT regexp_replace('.
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4 min readTo get unique values from 2 columns in PostgreSQL, you can use the DISTINCT keyword in combination with a SELECT statement. This will return only distinct combinations of values from the specified columns. Another way to achieve this is by using the UNION or UNION ALL operators to combine the results of two separate SELECT queries on each column and then applying the DISTINCT keyword on the combined result set.
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4 min readTo get the file extension from a filename in PostgreSQL, you can use the split_part function. This function allows you to split a string based on a specified delimiter and then retrieve a specific part based on its position. For example, if you have a filename "example.docx", you can use the following query to extract the file extension: SELECT split_part('example.docx', '.
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6 min readIn order to define the Hadoop classpath, you need to set the environment variable HADOOP_CLASSPATH. This variable should contain the path to the directory where the Hadoop configuration files are located, as well as any additional libraries that are required by your Hadoop application. You can set this environment variable either in your shell configuration file (such as .bashrc or .bash_profile) or in the script that starts your Hadoop application.
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4 min readTo store a mm/yyyy date on PostgreSQL, you can use the 'date' data type and store the date in the format 'yyyy-mm-01', where '01' represents the first day of the month. This way, you can easily query and manipulate date values using PostgreSQL functions and operators. It is important to ensure that the date is stored as a valid date value to prevent any issues with data retrieval and manipulation.
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5 min readTo increase the interval of a plot in Julia, you can use the xlim() and ylim() functions to set the limits of the x and y axes. For example, if you want to increase the interval of the x axis in a plot, you can use xlim() function to set the minimum and maximum values for the x axis. Similarly, for the y axis, you can use ylim() function to set the minimum and maximum values. This will increase the interval of the plot and adjust the range of values displayed on the axes.
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3 min readTo load a vector into a single column of an array in Julia, you can use the following code snippet: # Create a vector vector = [1, 2, 3, 4, 5] # Create an array with a single column array = zeros(Int, length(vector), 1) # Load the vector into the array array[:, 1] = vector In this code, we first create a vector with some values. Then, we create an array with the desired dimensions, where the second dimension has a size of 1 to represent a single column.