How Can I Efficiently Check for Row Existence in PostgreSQL Before Batch Inserts?

Efficiently Determining Row Existence in PostgreSQL

Inserting data into tables in batches requires a mechanism to ascertain whether a particular row exists to avoid redundant inserts. In PostgreSQL, leveraging the EXISTS keyword provides an effective approach to fulfill this requirement.

For instance, consider a batch of rows with the structure (userid, rightid, remaining_count). To check if any row within the batch exists in the contact table, use the following query:

SELECT EXISTS(SELECT 1 FROM contact WHERE userid=12)

This query evaluates to TRUE if a row with userid equals 12 exists in the contact table and FALSE otherwise. By checking this condition, you can determine the presence of all rows in the batch, as finding a single matching row implies the existence of the entire batch.

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