Delta Import (Incremental Sync)

If you sync the same file repeatedly (like a daily supplier feed), most rows are identical to last time. Delta Import skips those and only processes the rows that actually changed.

Why Use Delta Import

Say you have a 1 million product supplier feed that runs every night. In most days, only 500 products change price. Without delta:

• Every row is processed: 1 million writes
• Takes 3+ minutes

With delta:

• Only 500 rows are processed
• Takes 2 seconds

That is 150x faster.

How It Works

1. On the first import, the plugin computes a SHA-256 fingerprint of each row
2. Fingerprints are saved in a database table (wp_wkaie_row_hashes)
3. On the next import, the plugin compares each row to its saved fingerprint
4. If the fingerprint matches, the row is skipped (treated as unchanged)
5. If the fingerprint differs (even by one character), the row is processed

How to Turn On Delta Import

Screenshot: Step 3 — Delta Import lives alongside the preview/dry run, so you can confirm what will be skipped.

On the Quick Import Wizard

1. Wizard Step 3 → Scroll down to Delta Import
2. Check Skip unchanged rows
3. (Optional) Pick which columns count for the fingerprint

On Scheduled Jobs

1. Edit the job
2. Tab: Advanced
3. Check Delta Import
4. Save

Delta Import works on any entity, not just products.

Picking the Right Hash Columns

By default, the plugin hashes every column in the row. This means:

• If you change even a whitespace character, the row is considered changed
• If a new column is added (even unused), every row changes

You can pick specific columns to hash, like only the ones that matter.

Example

Your file has 50 columns: SKU, Name, Price, Stock, plus 46 others that never change. You only care about price and stock changes.

Set hash columns to:

• SKU
• Price
• Stock

Now changes in the other 46 columns do not trigger updates.

Watermark Approach

For very large imports, the plugin also supports a watermark approach:

• Pick a column like date_modified or last_updated
• Plugin remembers the highest watermark from the last run
• Next run, only rows with a higher watermark are processed

This is simpler than hashing but requires your source to have a reliable modified-date column.

When to Use Watermark

• Source has a date_modified column
• You trust that column to update when data changes
• You want the fastest possible delta

When to Use Hash (SHA-256)

• Source does not have a reliable modified-date column
• You want safety — hash catches any byte change
• You are okay with the small overhead of computing fingerprints

Reset Delta

Sometimes you want to force a full re-import (after a plugin update, schema change, etc.).

How to Reset

1. Go to Webkul WC Addons → Advance Import Export → Settings → Advanced
2. Click Reset Delta Hashes next to a job
3. Next import processes every row

Or via WP-CLI:

wp wkaie delta reset --job=42

Delta Import with Google Sheets

Screenshot: Google Sheets source — paired with Delta Import for a 5-minute live sync.

This is the killer combo. Your team edits a Google Sheet. The plugin runs every 5 minutes. Only changed cells update the store.

Setup

1. Create a scheduled job with source = Google Sheets
2. Turn on Delta Import
3. Set schedule to Every 5 minutes
4. Activate

Now your store auto-syncs with the sheet. Edit a cell, wait 5 minutes, see it in the store.

Performance Impact

Screenshot: Results page — showing total time and phase breakdown, where delta savings show up vividly.

Delta Import has two costs:

• Storage: Each row's fingerprint takes ~48 bytes in a database table. 1 million products = ~48 MB
• Compute: Hashing is fast (microseconds per row)

For a 1 million row table, the delta lookup takes about 1 second. Compared to the 3 minutes of a full re-import, that is a massive win.

What Counts as "Changed"

Every byte matters. These all count as different:

• Red Shirt vs Red shirt (case)
• Red Shirt vs Red Shirt (trailing space)
• 10.00 vs 10 (format)
• "Red Shirt" vs Red Shirt (quotes)

If your source includes random unrelated changes (like adding a trailing whitespace), delta will treat them as changed.

Workaround — Normalize First

Before hashing, you can normalize values:

1. In the wizard → Advanced → Delta Settings
2. Turn on Normalize before hash
3. Options: Lowercase, Trim whitespace, Strip HTML

Compared to the WP All Import Caching

If you used WP All Import before, their "caching" feature is similar but less robust:

Troubleshooting

Related Pages

• Scheduled Jobs — Run delta imports on a schedule
• Import Modes — Use with Create + Update mode
• Google Sheets source — The perfect pairing