Disable JIT by default in the Docker container

It's basically never faster in my testing, and often quite a bit slower.

Author: arp242

cmd/goatcounter/db.go

@@ -301,14 +301,6 @@ PostgreSQL notes:
 
         PGDATABASE=goatcounter PGHOST=/var/run goatcounter -db 'postgresql'
 
-    You may want to consider lowering the "seq_page_cost" parameter; the query
-    planner tends to prefer seq scans instead of index scans for some
-    operations with the default of 4, which is much slower. I found that 1.1 is
-    a fairly good setting, you can set it in your postgresql.conf file, or just
-    for one database with:
-
-        alter database goatcounter set seq_page_cost=1.1
-
 Converting from SQLite to PostgreSQL:
 
     You can use pgloader (https://pgloader.io) to convert from a SQLite to

compose.yaml

@@ -11,28 +11,30 @@ services:
     ports:    ['127.0.0.1:5432:5432']
     volumes:  ['postgres-data:/var/lib/postgresql/data']
     shm_size: '1gb'
+    environment:
+      'POSTGRES_USER':     'goatcounter'
+      'POSTGRES_PASSWORD': 'goatcounter'
+      'POSTGRES_DATABASE': 'goatcounter'
     command: [
-      '-c', 'shared_buffers=1GB',
-      '-c', 'effective_cache_size=10GB',
-      '-c', 'maintenance_work_mem=500MB',
-      '-c', 'work_mem=200MB',
-      '-c', 'wal_level=minimal',
+      '-c', 'shared_preload_libraries=pg_stat_statements',
+      '-c', 'default_statistics_target=1000',
+
+      '-c', 'wal_level=minimal',                  # WAL
       '-c', 'max_wal_senders=0',
       '-c', 'min_wal_size=256MB',
       '-c', 'max_wal_size=4GB',
-      '-c', 'random_page_cost=1.5',
-      '-c', 'effective_io_concurrency=256',
-      '-c', 'default_statistics_target=1000',
-      '-c', 'max_parallel_workers_per_gather=4',
+      '-c', 'shared_buffers=1GB',                 # Memory settings
+      '-c', 'effective_cache_size=10GB',
+      '-c', 'maintenance_work_mem=500MB',
+      '-c', 'work_mem=200MB',
+      '-c', 'max_parallel_workers_per_gather=4',  # Run queries in parallel
       '-c', 'max_parallel_maintenance_workers=4',
       '-c', 'max_worker_processes=8',
       '-c', 'max_parallel_workers=8',
-      '-c', 'shared_preload_libraries=pg_stat_statements',
+      '-c', 'random_page_cost=1.5',               # Most people use an SSD, and random page access is faster than HDDs.
+      '-c', 'effective_io_concurrency=256',       # SSDs are better at concurrent access.
+      '-c', 'jit=off',                            # Almost always slower.
     ]
-    environment:
-      'POSTGRES_USER':     'goatcounter'
-      'POSTGRES_PASSWORD': 'goatcounter'
-      'POSTGRES_DATABASE': 'goatcounter'
 
   # Don't start GoatCounter by default, but only if asked for with:
   #   docker compose up -d goatcounter-sqlite