Add tenant helper functions and improve migrate command

- Add migration 20_tenant_helper_functions.sql with list_tables() and describe_table()
- Show pending migrations before applying in `ow migrate run`

Author: max-lt

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "openworkers-cli"
-version = "0.2.0"
+version = "0.2.1"
 edition = "2024"
 license = "MIT"
 

Cargo.toml

@@ -0,0 +1,138 @@
+--
+-- OpenWorkers Database Schema - Tenant Helper Functions
+--
+-- Functions callable by tenants via PostGate using qualified names:
+--   SELECT * FROM postgate_helpers.list_tables();
+--   SELECT * FROM postgate_helpers.describe_table('users');
+--
+
+BEGIN;
+
+-- ============================================================================
+-- SCHEMA: postgate_helpers
+-- ============================================================================
+
+CREATE SCHEMA IF NOT EXISTS postgate_helpers;
+
+COMMENT ON SCHEMA postgate_helpers IS 'Utility functions for tenants (accessible via PostGate)';
+
+-- ============================================================================
+-- FUNCTION: list_tables()
+-- ============================================================================
+-- Lists all tables in the current tenant's schema with row counts.
+--
+-- Returns:
+--   table_name: Name of the table
+--   row_count: Number of rows in the table
+--
+-- Example:
+--   SELECT * FROM postgate_helpers.list_tables();
+
+CREATE OR REPLACE FUNCTION postgate_helpers.list_tables()
+RETURNS TABLE(table_name text, row_count bigint)
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+DECLARE
+    v_schema text;
+    tbl record;
+    cnt bigint;
+BEGIN
+    v_schema := current_schema();
+
+    -- Prevent access to system schemas
+    IF v_schema IN ('public', 'postgate_helpers') THEN
+        RAISE EXCEPTION 'Cannot list tables in system schemas';
+    END IF;
+
+    FOR tbl IN
+        SELECT tablename
+        FROM pg_tables
+        WHERE schemaname = v_schema
+        ORDER BY tablename
+    LOOP
+        EXECUTE format('SELECT count(*) FROM %I.%I', v_schema, tbl.tablename) INTO cnt;
+        table_name := tbl.tablename;
+        row_count := cnt;
+        RETURN NEXT;
+    END LOOP;
+END;
+$$;
+
+COMMENT ON FUNCTION postgate_helpers.list_tables() IS 'List all tables in the current tenant schema with row counts';
+
+-- ============================================================================
+-- FUNCTION: describe_table(table_name)
+-- ============================================================================
+-- Describes columns of a table in the current tenant's schema.
+--
+-- Parameters:
+--   p_table_name: Name of the table to describe
+--
+-- Returns:
+--   column_name: Name of the column
+--   data_type: PostgreSQL data type
+--   is_nullable: Whether the column allows NULL
+--   column_default: Default value expression
+--   is_primary_key: Whether the column is part of the primary key
+--
+-- Example:
+--   SELECT * FROM postgate_helpers.describe_table('users');
+
+CREATE OR REPLACE FUNCTION postgate_helpers.describe_table(p_table_name text)
+RETURNS TABLE(
+    column_name text,
+    data_type text,
+    is_nullable boolean,
+    column_default text,
+    is_primary_key boolean
+)
+LANGUAGE plpgsql
+SECURITY DEFINER
+AS $$
+DECLARE
+    v_schema text;
+BEGIN
+    v_schema := current_schema();
+
+    -- Prevent access to system schemas
+    IF v_schema IN ('public', 'postgate_helpers') THEN
+        RAISE EXCEPTION 'Cannot describe tables in system schemas';
+    END IF;
+
+    RETURN QUERY
+    SELECT
+        c.column_name::text,
+        c.data_type::text,
+        (c.is_nullable = 'YES')::boolean,
+        c.column_default::text,
+        COALESCE(
+            (SELECT true
+             FROM information_schema.table_constraints tc
+             JOIN information_schema.key_column_usage kcu
+                ON tc.constraint_name = kcu.constraint_name
+                AND tc.table_schema = kcu.table_schema
+             WHERE tc.constraint_type = 'PRIMARY KEY'
+                AND tc.table_schema = v_schema
+                AND tc.table_name = p_table_name
+                AND kcu.column_name = c.column_name
+             LIMIT 1),
+            false
+        )::boolean
+    FROM information_schema.columns c
+    WHERE c.table_schema = v_schema
+        AND c.table_name = p_table_name
+    ORDER BY c.ordinal_position;
+END;
+$$;
+
+COMMENT ON FUNCTION postgate_helpers.describe_table(text) IS 'Describe columns of a table in the current tenant schema';
+
+-- ============================================================================
+-- PERMISSIONS
+-- ============================================================================
+
+GRANT USAGE ON SCHEMA postgate_helpers TO PUBLIC;
+GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA postgate_helpers TO PUBLIC;
+
+COMMIT;

migrations/20_tenant_helper_functions.sql

@@ -83,7 +83,30 @@ async fn connect(database_url: &str) -> Result<PgPool, MigrateError> {
 }
 
 async fn cmd_run(pool: &PgPool) -> Result<(), MigrateError> {
-    println!("Running migrations...\n");
+    // Get already applied migrations
+    let applied: Vec<i64> = sqlx::query_scalar("SELECT version FROM _sqlx_migrations")
+        .fetch_all(pool)
+        .await
+        .unwrap_or_default();
+
+    // Find pending migrations
+    let pending: Vec<_> = MIGRATOR
+        .iter()
+        .filter(|m| !applied.contains(&m.version))
+        .collect();
+
+    if pending.is_empty() {
+        println!("{}", "No pending migrations.".green());
+        return Ok(());
+    }
+
+    println!("Running {} migration(s)...\n", pending.len());
+
+    for migration in &pending {
+        println!("  {} {}", "Applying".blue(), migration.description);
+    }
+
+    println!();
 
     MIGRATOR.run(pool).await?;