init db and docker

db/init.sql

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+-- URL Shortener Database Schema
+
+CREATE TABLE IF NOT EXISTS urls (
+    id BIGSERIAL PRIMARY KEY,
+    short_code VARCHAR(10) UNIQUE NOT NULL,
+    original_url TEXT NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    expires_at TIMESTAMP WITH TIME ZONE,
+    click_count BIGINT DEFAULT 0,
+
+    -- Metadata
+    user_agent TEXT,
+    ip_address INET
+);
+
+-- Index for fast lookups by short_code (most common query)
+CREATE INDEX idx_urls_short_code ON urls(short_code);
+
+-- Index for cleanup of expired URLs
+CREATE INDEX idx_urls_expires_at ON urls(expires_at) WHERE expires_at IS NOT NULL;
+
+-- Analytics table (for click tracking)
+CREATE TABLE IF NOT EXISTS clicks (
+    id BIGSERIAL PRIMARY KEY,
+    short_code VARCHAR(10) NOT NULL,
+    clicked_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
+    ip_address INET,
+    user_agent TEXT,
+    referer TEXT,
+    country_code VARCHAR(2)
+);
+
+-- Partition-friendly index (clicks will be high volume)
+CREATE INDEX idx_clicks_short_code ON clicks(short_code);
+CREATE INDEX idx_clicks_clicked_at ON clicks(clicked_at);
+
+-- Function to increment click count (atomic)
+CREATE OR REPLACE FUNCTION increment_click_count(code VARCHAR(10))
+RETURNS VOID AS $$
+BEGIN
+    UPDATE urls SET click_count = click_count + 1 WHERE short_code = code;
+END;
+$$ LANGUAGE plpgsql;