Otimizando tempo de carregamento da tabela

server/services/eventos.js

@@ -2,7 +2,9 @@
 
 const dbRecords = _db.query(`
     SELECT evento.titulo, to_char(evento.data, 'DD/MM/YYYY') AS data, evento.capacidade, 
-    evento.preco, categoria_evento.nome AS categoria 
+    evento.preco, categoria_evento.nome AS categoria,
+	(SELECT count(*) FROM evento evento2 WHERE evento2.id_categoria = evento.id_categoria) as quantia, 
+	ROW_NUMBER () OVER (PARTITION BY categoria_evento.id ORDER BY categoria_evento.nome) as linha
     FROM evento JOIN categoria_evento ON evento.id_categoria = categoria_evento.id ORDER BY categoria
 `);
 
@@ -19,20 +21,25 @@ _out.println('<div style="display: flex; justify-content: center; margin-top: 80
                 _out.println('<th style="border-collapse:collapse; border:1px solid #999; border-inline:none;">Categoria</th>')
             _out.println('</tr>')
             
-            let copiaDbRecords = dbRecords.slice()
+//            let copiaDbRecords = dbRecords.slice()
 
             dbRecords.map(dbRecord => {
  
-                 const initialLength = copiaDbRecords.length
-                 copiaDbRecords = copiaDbRecords.filter(r => r.getString("categoria") != dbRecord.getString("categoria"))
-                 const lengthCategoria = initialLength - copiaDbRecords.length                                     
+//                 const initialLength = copiaDbRecords.length
+//                 copiaDbRecords = copiaDbRecords.filter(r => r.getString("categoria") != dbRecord.getString("categoria"))
+//                 const lengthCategoria = initialLength - copiaDbRecords.length                                     
+                
+                 const quantia = dbRecord.getInt("quantia")   
+                 const linha = dbRecord.getInt("linha")
+                 const imprimeCategoria = (quantia > 1 && linha === 1) || quantia === 1
 
                 _out.println(`<tr style="height:35px;">`)
                     _out.println(`<td style="border-collapse:collapse; border:1px solid #999; border-inline:none;">${dbRecord.getString("titulo")}</td>`)
                     _out.println(`<td style="border-collapse:collapse; border:1px solid #999; border-inline:none;">${dbRecord.getString("data")}</td>`)
                     _out.println(`<td style="border-collapse:collapse; border:1px solid #999; border-inline:none;">${dbRecord.getInt("capacidade")}</td>`)
                     _out.println(`<td style="border-collapse:collapse; border:1px solid #999; border-inline:none;">${dbRecord.getDouble("preco")}</td>`)
-                    {lengthCategoria > 0 && _out.println(`<td style="border-collapse:collapse; border:1px solid #999; border-inline:none;" rowspan="${lengthCategoria}">${dbRecord.getString("categoria")}</td>`)}
+                    {imprimeCategoria _out.println(`<td style="border-collapse:collapse; border:1px solid #999; border-inline:none;" rowspan="${quantia}">${dbRecord.getString("categoria")}</td>`)}
+                    
                 _out.println('</tr>')
             })