fix: avoid recording a duplicate price_history row on every scheduled check

[Osamaali313]

Summary

The scheduler's dedup guard never matches, so an identical price_history row is written on every scheduled check even when the price hasn't changed.

backend/src/services/scheduler.ts:

const latestPrice = await priceHistoryQueries.getLatest(product.id);
// Only record if price has changed or it's the first entry
if (!latestPrice || latestPrice.price !== scrapedData.price.price) {

price_history.price is DECIMAL(10,2), and node-postgres returns DECIMAL/NUMERIC as a string (there's no pg.types.setTypeParser in the repo). So latestPrice.price is "19.99" while scrapedData.price.price is the number 19.99. !== does no coercion, so "19.99" !== 19.99 is always true and the guard passes every time.

The intent is clearly to skip unchanged prices — the comment says so and the else branch logs Price unchanged for product ..., which is currently unreachable. The neighbouring price-drop and target-price checks already coerce with parseFloat(String(latestPrice.price)); this one comparison just missed it.

Impact

At the default 1-hour refresh_interval, each product accumulates ~24 identical rows per day. price_history grows without bound, the "Price unchanged" optimization is dead code, and the price chart / price_count stat get padded with redundant points. (Notifications are unaffected — the drop/target checks use parseFloat, so a zero delta correctly fails the threshold.)

Fix

Coerce the stored value before comparing, matching what the surrounding checks already do:

if (!latestPrice || parseFloat(String(latestPrice.price)) !== scrapedData.price.price) {

An actual price change still records a new row; an unchanged price now correctly hits the else branch.

Testing

The repo has no test harness, so I verified by tracing the runtime types: getLatest returns the raw pg row (price as string), PriceInfo.price is typed number and produced via parseFloat, and there is no global decimal type parser. Happy to add a small priceChanged() helper + unit test if you'd like a harness set up.

[Copilot]

Pull request overview

This PR fixes the scheduler’s “record price only when changed” dedup guard by coercing the latest stored price_history.price (returned from pg as a string for DECIMAL/NUMERIC) to a number before comparing it to the freshly scraped numeric price. This prevents writing redundant price_history rows on every scheduled run when the price has not changed.

Changes:

• Coerce latestPrice.price with parseFloat(String(...)) before comparing to scrapedData.price.price.
• Add an inline comment explaining the pg DECIMAL string vs number mismatch and why coercion is needed.

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