Hi @sakuraime , welcome to Microsoft Q&A forum.
To address your query, currently there is no mechanism to migrate the data from PostgreSQL to Azure Database for PostgreSQL using pg_dump and pg_restore for incremental data sync.
However to lower the downtime, you can use a high compute and high memory sku, like 32 vCore Memory Optimized, to speed up the migration. You can easily scale back down to your preferred sku after the restore is complete. The higher the sku, the more parallelism you can achieve by increasing the corresponding -j parameter in the pg_restore command. (refer to link)
Alternative approach is to use the Azure Data Factory to create a pipeline to migrate incremental data but it cannot use the dump file. For more details refer to below link:
https://techcommunity.microsoft.com/t5/azure-database-for-postgresql/bring-your-data-to-azure-database-for-postgresql-hyperscale/ba-p/857975
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