Salesforce Data Loader and Duplicate Records Management

If batch size is set to 1
what is the performance degradation?
(a lot!)

Problem Statement

When loading a Salesforce database using Data Loader, and in order to have Salesforce properly detect duplicate records that may exist in the input file, then turn on duplicate record detection in Setup, and set Data Loader batch size to one. Records in a Data Loader input file are committed to the Salesforce database in increments equal to batch size, and if it is set to one then duplicates in the input file will be detected by Salesforce duplicate management. For details on how to configure and activate Salesforce duplicate record management please see this article:

The disadvantage of setting batch size to one is that it significantly degrades performance, as shown in the table below.

Batch Size
Insert 2,500
Delete 2,500
35 Seconds
24 Seconds

24 Minutes
18 Minutes
28 Seconds
24 Minutes

Following are some comparisons of execution time using three different batch size values.

Load and delete 2,500 accounts with batch size = 200

This seems to be the Data Loader default. With batch size set to 200, using Data Loader, 2,500 accounts were loaded into a developer org. This consistently took 35 seconds to run. Deleting the same 2,500 accounts using Data Loader consistently took 24 seconds.

Data Loader is the tool of choice if the number of input records exceeds the 50,000 record capacity of Data Import Wizard. Tests and measurements conducted for this article were done using a developer org which has capacity limitations precluding use of larger input data sets.

A Wire Shark packet trace and the Mac’s Activity Monitor shows the batch size value controls not only update denomination, but transmission as well. Records are to be transmitted from a user’s computer to the Salesforce host in increments equal to the batch size value. Network latency is almost certainly greater than database latency, so the question becomes how much of the performance degradation is due to network latency, and how much of it is database latency on the host side?

The following graph from Mac Activity Monitor shows transmitted and received bytes during the 35 seconds it took to load 2,500 accounts with batch size set to 200. The red area indicates bytes transmitted, which is the data, and the blue area represents bytes received, which is the TCP acknowledgements and progress messages.

Send Receive batch size 200
Bytes sent (red) and received (blue)

When running the delete transaction, the size of a data packet sent, containing only the record ID, is small and close to the size of the returned acknowledgement. That would explain the following graph, recorded during the 24 seconds it takes to delete 2,500 account records using a batch size of 200. The graph shows an approximately equal number of bytes sent and received during the delete process.

Bytes sent and received during delete with batch size =
Bytes sent (red) and received (blue)

Load and delete 2,500 accounts with batch size = 1

With batch size set to one, it took 24 minutes to load the same 2,500 account records into the developer org. It took 16 minutes to delete the accounts.

When batch size is set to one the insert process is painfully slow, at about 1.7 records per second. Data transfer during the insert transaction consistently shows an approximately equal quantity of bytes sent and received, as shown in the following graph. The Wire Shark packet trace shows one record is sent for each acknowledgement received.

Send receive batch size 1
Bytes sent (red) and received (blue)

Load and delete 2,500 accounts with batch size = 2600

With “Use Bulk API” enabled and batch size set to 2,600, it took 28 seconds to load the same 2,500 accounts, and 24 seconds to delete. I used batch size of 2,600 to ensure the entire input file, of 2,500 records, would be transferred and committed at one time. The following graph, from Mac Activity Monitor, shows bytes sent and received during insert execution of 2,500 accounts with batch size is set to 2,600 and ‘Use Bulk API’ is checked. This is a fast execution, 28 seconds, and it would appear from the graph that all 2,500 records were transmitted to a host in a very short interval. The red area represents bytes sent and the blue area is bytes received.

Send and Received batch size 2600
Bytes sent (red) and received (blue)

A different pattern is visible during the 24 seconds it took to delete the 2,500 account records with batch size set to 2,600. The volume of bytes received, shown in red, is approximately equal to the volume of bytes sent, shown in blue. This would appear consistent with the previous graph of a delete transaction, with the delete record and acknowledgement being about the same size.

Delete bs 2600
Bytes sent (red) and received (blue)


The difference in wall-clock time to update or delete records in Salesforce using Data Loader varies with surprising significance depending on the value of batch size. Using a batch size of one causes updates and deletes to be inordinately slow.

The Wire Shark packet traces prove that insert and delete records are transmitted to the Salesforce host in increments equal to the batch size. This raises the question of whether the painfully slow update rates observed are the result of network latency or latency on the database host. These tests were conducted from a home office with, a relatively slow residential cable connection to the internet, using a developer org of limited data storage capacity. Test results may look different when run from a client with a faster network connection. Stay tuned for that update in an upcoming report.

Right now the test results suggest a batch size of one, necessary to detect duplicates within an input file, significantly slows the update process, inducing a tremendous performance penalty that many users may find unacceptable.