Implement PostgreSQL upgrade and rollback scripts, update docker-compose for PostgreSQL version 17.5, and enhance .gitignore to include backup files. Add README for upgrade instructions.

rollback_postgres_upgrade.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+COMPOSE=./docker-compose.yaml
+SERVICE=postgres
+DATA_DIR=./database
+ROLLBACK_TIMESTAMP=$(date +%Y%m%d_%H%M%S)
+
+echo "🧪 Validating docker-compose config..."
+docker compose -f "$COMPOSE" config > /dev/null || {
+  echo "❌ docker-compose config failed. Restore aborted."
+  exit 1
+}
+
+# Extract current Postgres image
+CURRENT_IMG=$(docker compose -f "$COMPOSE" config | grep "image:" | grep "$SERVICE" | awk '{print $2}' || true)
+
+if [[ -z "$CURRENT_IMG" ]]; then
+  echo "❌ Could not detect current image for service '$SERVICE'."
+  exit 1
+fi
+
+CURRENT_TAG=$(basename "$CURRENT_IMG")
+CURRENT_VERSION=$(echo "$CURRENT_TAG" | cut -d'-' -f1) # e.g., 17.5
+
+# Detect appropriate backup folder
+BACKUP_CANDIDATES=($(ls -td ./database_backup_* 2>/dev/null || true))
+
+if [[ ${#BACKUP_CANDIDATES[@]} -eq 0 ]]; then
+  echo "❌ No backup directory found. Cannot determine previous version."
+  echo "ℹ️ Available folders:"
+  ls -1d ./database_backup_* || true
+  exit 1
+elif [[ ${#BACKUP_CANDIDATES[@]} -eq 1 ]]; then
+  SELECTED_BACKUP="${BACKUP_CANDIDATES[0]}"
+  echo "ℹ️ Only one backup found. Using: ${SELECTED_BACKUP}"
+else
+  SELECTED_BACKUP="${BACKUP_CANDIDATES[1]}"
+  echo "ℹ️ Multiple backups found. Using second latest: ${SELECTED_BACKUP}"
+fi
+
+# Extract version from selected backup folder
+OLD_TAG=$(basename "$SELECTED_BACKUP" | sed -E 's/database_backup_(([^_]+)-alpine).*/\1/')
+OLD_IMG="postgres:${OLD_TAG}"
+
+DELETED_UPGRADE_DIR=./database_upgraded_${CURRENT_VERSION}_${ROLLBACK_TIMESTAMP}
+
+echo "⏪ Initiating rollback from Postgres ${CURRENT_TAG} to ${OLD_IMG}..."
+
+# Step 1: Confirm backup exists
+if [ ! -d "$SELECTED_BACKUP" ]; then
+  echo "❌ Backup folder '${SELECTED_BACKUP}' not found. Aborting."
+  exit 1
+fi
+
+# Step 2: Stop services
+echo "🛑 Stopping running services..."
+docker compose -f "$COMPOSE" down
+
+# Step 3: Archive current (possibly broken) database
+echo "📦 Archiving current database directory as '${DELETED_UPGRADE_DIR}'..."
+mv "$DATA_DIR" "$DELETED_UPGRADE_DIR"
+
+# Step 4: Restore previous version
+echo "♻️ Restoring from backup folder '${SELECTED_BACKUP}'..."
+cp -a "$SELECTED_BACKUP" "$DATA_DIR"
+
+# Step 5: Restore image tag in docker-compose.yaml
+echo "🔁 Reverting docker-compose image tag to Postgres ${OLD_IMG}..."
+update_image_tag() {
+  local svc="$1"
+  local file="$2"
+  local target_tag="$3"
+  
+  echo "🔁 Reverting docker-compose image tag for service '$svc' to Postgres: ${target_tag}..."
+
+  # Use awk to scope updates within the service definition only
+  awk -v service="$svc" -v new_tag="$target_tag" '
+    BEGIN { in_service = 0 }
+    /^[ ]{2}[a-zA-Z0-9_-]+:/ {
+      in_service = ($1 == service ":") ? 1 : 0
+    }
+    in_service && /^\s*image:/ {
+      sub(/postgres:[^"'"'"']+/, "postgres:" new_tag)
+    }
+    { print }
+  ' "$file" > "${file}.tmp" && mv "${file}.tmp" "$file"
+}
+update_image_tag "$SERVICE" "$COMPOSE" "$OLD_TAG"
+
+# Step 6: Restart Postgres
+echo "🚀 Starting Postgres service with restored image..."
+docker compose -f "$COMPOSE" up -d "$SERVICE"
+
+# Step 7: Final messages
+echo "✅ Rollback complete!"
+echo "🗃️ PostgreSQL downgraded to '${OLD_IMG}' and data restored from '${SELECTED_BACKUP}'."
+echo "📦 The faulty upgrade has been archived in '${DELETED_UPGRADE_DIR}'."
+echo "  - To clean: rm -rf ${DELETED_UPGRADE_DIR}"
+echo "  - To verify: docker compose logs -f $SERVICE"
+
+# Step 8: Restart full application
+echo "🔄 Pulling latest images..."
+if ! docker compose pull; then
+  echo "❌ Failed to pull images. Aborting."
+  exit 1
+fi
+
+echo "🔄 Starting full application stack..."
+if ! docker compose up -d --force-recreate; then
+  echo "❌ Failed to start application stack. Please check logs."
+  exit 1
+fi
+
+echo "✅ Deployment completed successfully."