![]() The following LINQ query symbolizes our intent but throws an InvalidOperationException at runtime because a Join of an EF-query with an in-memory collection is not supported.Īdding support for temp tables to Entity Framework Core can be divided into three parts: introduction of temp tables to Entity Framework Core, creation of the temp tables, and inserting records. However, working with a collection of simple values like productIds is not the same as having a collection of tuples because we can not use Contains() anymore but need the method Join().Ī concrete example would be loading OrderItems for specific customers and products. The previous example may not yield the best performance when using built-in features only, but it is supported by Entity Framework Core. With unique, ordered data, the database should be able to choose the best operations to process the request. By this, the database receives important information, so the records are unique and ordered. In our case, we can insert all productIds into a temp table and create a unique (clustered) index. Last but not least, we can provide the database with more information about the data, so the database can to choose a better execution plan. Furthermore, we may choose a more performant approach to send the identifiers to the database like using SqlBulkCopy in case of MS SQL Server. (I think this technique will work for any versions of MySQL since 4.1, plus MariaDB.One benefit of the temp tables is that we do not need to send the same data like productIds multiple times to the database when using it in multiple queries. The table could be created with an AUTO_INCREMENT column, but I don't see any particular need for such. Multiple calls to Spray() will add more rows. If _string might be more than a megabyte long, you will probably need to split it into chunks. To break a sentence into words (assuming one space between words), change some datatypes, and change the REPLACE to REPLACE(_string, ' ', '"),("' ) The table built and the intermediate SQL that populated it: mysql> SELECT * FROM test_spray Inner join table2 on CHAR_LENGTH(table2.bar)-CHAR_LENGTH(REPLACE(table2.bar, ',', ''))>=numbers.nr-1Ī faster solution (no looping, no splitting):ĬREATE PROCEDURE Spray(IN _table VARCHAR(64), SUBSTRING_INDEX(SUBSTRING_INDEX(table2.bar, ',', numbers.nr), ',', -1) as itemid Then use following query: select * from table1 where itemid in ( INNER JOIN temp_string ts ON t1.itemid=ts.vals Īnother approach would be creating a numbers table with the max length (how many comma separated values) of your string Then you can call it and use it on the join condition : call splitString('3363134,5189076',',') ![]() SELECT TRIM(vals) as my_string_split FROM temp_string INSERT INTO temp_string(vals) VALUES(inputString) SET inputString = REPLACE(inputString, (SELECT LEFT(inputString, LOCATE(delimiterChar, inputString))),'') INSERT INTO temp_string SELECT SUBSTRING_INDEX(inputString,delimiterChar,1) WHILE LOCATE(delimiterChar,inputString) > 1 DO One not so optimal way is create a stored procedure which split the string like below: DELIMITER //ĭROP TEMPORARY TABLE IF EXISTS temp_string ĬREATE TEMPORARY TABLE temp_string(vals text) In MySQL it is quite hard to split a string, because there is no built in function.
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