Optimize memory usage in item data processing (#317)

The commit replaces two 'const' declarations with 'let' in 'item-data-processing.ts' for rawData and rawDataArray. After these variables are used, they are set to null, freeing up memory space. The change is aimed at optimizing memory usage and improving performance.

src/server/controllers/item/shared/item-data-processing.ts

@@ -55,11 +55,13 @@ export const itemDataProcessing = async ({ projectName, scenarioName, itemId })
         const responseFailures = await db.manyOrNone(responseMessageFailures(itemId))
         const scenarioSettings = await db.one(getScenarioSettings(projectName, scenarioName))
 
-        const rawData = await db.manyOrNone(findRawData(itemId))
-        const rawDataArray = rawData?.map(row => [moment(row.timestamp).valueOf(), row.elapsed])
+        let rawData = await db.manyOrNone(findRawData(itemId))
+        let rawDataArray = rawData?.map(row => [moment(row.timestamp).valueOf(), row.elapsed])
         const rawDataDownSampled = downsampleData(rawDataArray, MAX_SCATTER_CHART_POINTS)
         const groupedErrors = await db.manyOrNone(findGroupedErrors(itemId))
         const top5ErrorsByLabel = await db.manyOrNone(findTop5ErrorsByLabel(itemId))
+        rawData = null
+        rawDataArray = null
 
         if (aggOverview.number_of_sut_hostnames > 1) {
             sutMetrics = await db.many(sutOverviewQuery(itemId))
@@ -76,7 +78,6 @@ export const itemDataProcessing = async ({ projectName, scenarioName, itemId })
             }))
         }
 
-
         const {
             overview,
             overview: { duration },