added migration for anonymous user identification by browser ID

migrations/005_browser_id.sql

@@ -0,0 +1,27 @@
+-- =====================================================================
+-- Migration 005: Adds Browser ID for anonymous User Identification
+-- =====================================================================
+
+-- Adds browser_id Column to Contributions
+ALTER TABLE contributions
+    ADD COLUMN browser_id VARCHAR(36) DEFAULT NULL;
+
+-- Adds browser_id Column to Votes
+-- Replaces voter_name for Identification
+ALTER TABLE votes
+    ADD COLUMN browser_id VARCHAR(36) DEFAULT NULL;
+
+-- Index for fast Vote Lookup by Browser
+CREATE INDEX idx_votes_browser ON votes(browser_id);
+
+
+-- New UNIQUE Constraint: One Vote per Browser per Contribution
+
+-- Drops old Constraint voter_name based
+ALTER TABLE votes
+    DROP CONSTRAINT IF EXISTS votes_contribution_id_voter_name_key;
+
+-- Creates new Constraint browser_id based
+ALTER TABLE votes
+    ADD CONSTRAINT votes_contribution_browser_unique
+    UNIQUE (contribution_id, browser_id);