How-To Guides¶

Practical recipes for common mongo2pg tasks.

How to set up a migration project¶

Use mongo2pg init to create a repeatable project directory:

mongo2pg init \
  --project-base ./projects \
  --project-name airbnb \
  --source-uri mongodb://localhost:27017 \
  --target-uri postgres://postgres:x@localhost:5432/postgres?sslmode=disable \
  --namespace sample_airbnb

This creates:

projects/airbnb/
  config/
    airbnb.toml
  source/
    collections/
  schema/
    tables/
  data/
  reports/

You can then pass -c projects/airbnb/config/airbnb.toml to subsequent commands instead of repeating all flags.

How to infer schemas¶

Single collection¶

mongo2pg infer \
  --source-uri mongodb://localhost:27017 \
  --namespace sample_airbnb.listingsAndReviews \
  --output-dir ./output \
  --number 2000

All collections in a database¶

mongo2pg infer \
  --source-uri mongodb://localhost:27017 \
  --namespace sample_airbnb \
  --output-dir ./output

With -c <config>, infer also refreshes SQL files under schema/tables/ and the main reports under reports/.

How to export relational CSV files¶

mongo2pg export -c ./projects/airbnb/config/airbnb.toml

This expands nested documents and arrays into one .csv.gz file per generated PostgreSQL table.

How to load PostgreSQL objects and data¶

mongo2pg import -c ./projects/airbnb/config/airbnb.toml

This command:

• connects to PostgreSQL using TARGET_URI
• creates the target database if needed
• executes schema/tables/<db>/*.sql
• decompresses each exported .csv.gz file and loads it with COPY

How to validate a PostgreSQL import¶

Set both SOURCE_URI and TARGET_URI in the config file, then run:

mongo2pg report \
  -c ./projects/airbnb/config/airbnb.toml \
  --post-import

This generates reports/post_report.html, which compares:

• MongoDB top-level document counts
• MongoDB expanded nested occurrence counts
• PostgreSQL row counts per generated table

The report highlights where counts match and where they differ.