Avoid failure when public schema already exists. Minor docs improvement

Author: rustprooflabs

README.md

@@ -38,9 +38,8 @@ The easiest option to use PgOSM-Flex is with the
 The image has all the pre-reqs installed, handles downloading an OSM subregion
 from Geofabrik, and saves an output `.sql` file with the processed data
 ready to load into your database(s).
-
-The script in the Docker image uses `PGOSM_DATE` to enable the Docker process
-to archive source PBF files and easily reload them at a later date.
+The PBF/MD5 source files are archived by date with the ability to
+easily reload them at a later date.
 
 
 ### Basic Docker usage
@@ -97,18 +96,36 @@ docker exec -it \
     --subregion=district-of-columbia
 ```
 
-
 The initial output with the `docker exec` command points to the log file
 (linked in the `docker run` command above), monitor this file to track
 progress of the import.
 
-
 ```bash
 Monitor /app/output/district-of-columbia.log for progress...
 If paths setup as outlined in README.md, use:
     tail -f ~/pgosm-data/district-of-columbia.log
 ```
 
+The above command takes roughly 1 minute to run if the PBF for today
+has already been downloaded.
+If the PBF is not downloaded it will depend on how long
+it takes to download the 17 MB PBF file + ~ 1 minute processing.
+
+The output `.sql` file is saved under
+`~/pgosm_data/pgosm-flex-north-america-us-district-of-columbia-run-all.sql`.
+This `.sql` file can be loaded into a PostGIS enabled database
+using:
+
+```bash
+psql -d postgres -c "CREATE DATABASE myosm;"
+psql -d myosm -c "CREATE EXTENSION postgis;"
+```
+
+```bash
+psql -d myosm \
+    -f ~/pgosm-data/pgosm-flex-north-america-us-district-of-columbia-run-all.sql
+```
+
 
 ### After processing
 

docker/db.py

@@ -6,6 +6,8 @@
 import subprocess
 
 import psycopg2
+import sh
+
 
 LOGGER = logging.getLogger('pgosm-flex')
 
@@ -362,3 +364,17 @@ def run_pg_dump(export_filename, out_path, data_only, schema_name):
                             check=False)
     LOGGER.info(f'pg_dump complete, saved to {export_path}')
     LOGGER.debug(f'pg_dump output: \n {output.stderr}')
+    fix_pg_dump_create_public(export_path)
+
+
+def fix_pg_dump_create_public(export_path):
+    """Using pg_dump with `--schema=public` results in
+    a .sql script containing `CREATE SCHEMA public;`, nearly always breaks
+    in target DB.  Replaces with `CREATE SCHEMA IF NOT EXISTS public;`
+    """
+    result = sh.sed('-i',
+           's/CREATE SCHEMA public;/CREATE SCHEMA IF NOT EXISTS public;/',
+           export_path)
+    LOGGER.debug('Completed replacement to not fail when public schema exists')
+    LOGGER.debug(result)
+

requirements.txt

@@ -2,3 +2,4 @@ click>=8.0.1
 coverage>=5.5
 psycopg2>=2.8.6
 requests>=2.26.0
+sh>=1.14.2