Page:: merge()

Used to perform data cleaning through merging duplicates to a single record. This is done from the crud page where the currently checked records can be merged.

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    public async merge():Promise<void>{

Description

Collect the data to merge:-

• De-structure the subject to reveal the database and reference table.

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          const [ename, dbname] = this.subject;  
  

• Collect the primary keys of checked records.

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          const nodelist = this.document.querySelectorAll(
              "input[name='multi_select']:checked"
          );
  

Convert the node-list keys to an array of key values.

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           const keys = (Array.from(nodelist)).map(
               element=>(<HTMLInputElement>element).value
           );

For the merging, there must be at least two selected keys.

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           if (keys.length<2){
               alert(`There must be at least 2 records to merge. Found ${keys.length}`);
               return;
           }

To retrieve the members to merge, formulate an SQL query from the checked records. And convert the names to backtick enclosed strings.

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       const dbname_str = "`" + dbname + "`";
        const ename_str = "`" + ename + "`";
        //
        const members = 
            `select
                ${dbname_str}.${ename_str}.${ename_str} as member 
            from 
                ${dbname_str}.${ename_str}
            where 
                ${dbname_str}.${ename_str}.${ename_str} in (${keys.join(', ')})`; 

Compile the imerger structure.

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        const imerger = {ename, dbname, members};

Create a new object keeping in mind the merger class extends a baby.

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        const Merger = new merger(imerger, this)

Wait for the merging process to finish. The result is the primary key of the principal(main) that represents the merged members.

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        const principal:number|undefined = await Merger.administer();

Use the principal to update the page and highlight the record if need be, wait for the page to refresh , then get the table-row that matches the principal and select it.

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        if (principal!==undefined){
            await this.review();
        }      
    }