From ebbe2915c64db39a2dafa8d9a9491ee21fdce23d Mon Sep 17 00:00:00 2001
From: Matthew Bucci <buccim2@gene.com>
Date: Wed, 21 Feb 2024 01:15:51 -0800
Subject: [PATCH] add rewrite logic for SHOW TABLE STATUS and a catch for calls
 to information_schema

---
 pg4wp/driver_pgsql_rewrite.php                |  2 +-
 pg4wp/rewriters/SelectSQLRewriter.php         | 35 ++++++++++++
 .../rewriters/ShowTableStatusSQLRewriter.php  | 54 +++++++++++++++++++
 3 files changed, 90 insertions(+), 1 deletion(-)
 create mode 100644 pg4wp/rewriters/ShowTableStatusSQLRewriter.php

diff --git a/pg4wp/driver_pgsql_rewrite.php b/pg4wp/driver_pgsql_rewrite.php
index 0292cd0..d666d28 100644
--- a/pg4wp/driver_pgsql_rewrite.php
+++ b/pg4wp/driver_pgsql_rewrite.php
@@ -12,7 +12,7 @@ spl_autoload_register(function ($className) {
 function createSQLRewriter(string $sql): AbstractSQLRewriter
 {
     $sql = trim($sql);
-    if (preg_match('/^(SELECT|INSERT|UPDATE|DELETE|DESCRIBE|ALTER TABLE|CREATE TABLE|DROP TABLE|SHOW INDEX|SHOW VARIABLES|SHOW TABLES|OPTIMIZE TABLE|SET NAMES|SHOW FULL COLUMNS)\b/i', $sql, $matches)) {
+    if (preg_match('/^(SELECT|INSERT|UPDATE|DELETE|DESCRIBE|ALTER TABLE|CREATE TABLE|DROP TABLE|SHOW INDEX|SHOW VARIABLES|SHOW TABLES|OPTIMIZE TABLE|SET NAMES|SHOW FULL COLUMNS|SHOW TABLE STATUS)\b/i', $sql, $matches)) {
         // Convert to a format suitable for class names (e.g., "SHOW TABLES" becomes "ShowTables")
         $type = str_replace(' ', '', ucwords(str_replace('_', ' ', strtolower($matches[1]))));
         $className = $type . 'SQLRewriter';
diff --git a/pg4wp/rewriters/SelectSQLRewriter.php b/pg4wp/rewriters/SelectSQLRewriter.php
index 90b6d37..e8e0e8a 100644
--- a/pg4wp/rewriters/SelectSQLRewriter.php
+++ b/pg4wp/rewriters/SelectSQLRewriter.php
@@ -31,6 +31,16 @@ class SelectSQLRewriter extends AbstractSQLRewriter
             $sql = preg_replace('/SELECT\s+.*?\s+FROM\s+/is', 'SELECT COUNT(*) FROM ', $sql, 1);
         }
 
+        if(false !== strpos($sql, 'information_schema')) {
+            // WP Site Health rewrites
+            if (false !== strpos($sql, "SELECT TABLE_NAME AS 'table', TABLE_ROWS AS 'rows', SUM(data_length + index_length)")) {
+                $sql = $this->postgresTableSizeRewrite(); 
+                return $sql;
+            }
+
+            throw new Exception("Unsupported call to information_schema, this probably won't work correctly and needs to be specifically handled, open a github issue with the SQL");
+        }
+
         $sql = $this->ensureOrderByInSelect($sql);
 
         // Convert CONVERT to CAST
@@ -347,4 +357,29 @@ class SelectSQLRewriter extends AbstractSQLRewriter
         return $sql;
     }
 
+    // This method is specifically to handle should_suggest_persistent_object_cache in wp site health
+    protected function postgresTableSizeRewrite() 
+    {
+
+        $sql = <<<SQL
+        SELECT 
+            C.relname AS "table", 
+            S.n_live_tup AS "rows", 
+            pg_total_relation_size(C.oid) AS "bytes"
+        FROM 
+            pg_class C 
+        LEFT JOIN 
+            pg_namespace N ON (N.oid = C.relnamespace) 
+        INNER JOIN 
+            pg_stat_user_tables S ON (S.relid = C.oid) 
+        WHERE 
+            N.nspname = 'public' AND 
+            C.relname IN ('wp_comments','wp_options','wp_posts','wp_terms','wp_users')
+        GROUP BY 
+            C.relname, pg_total_relation_size(C.oid), S.n_live_tup;
+        SQL;
+
+        return $sql;
+    }
+
 }
diff --git a/pg4wp/rewriters/ShowTableStatusSQLRewriter.php b/pg4wp/rewriters/ShowTableStatusSQLRewriter.php
new file mode 100644
index 0000000..346d721
--- /dev/null
+++ b/pg4wp/rewriters/ShowTableStatusSQLRewriter.php
@@ -0,0 +1,54 @@
+<?php
+
+class ShowTableStatusSQLRewriter extends AbstractSQLRewriter
+{
+    public function rewrite(): string
+    {
+        $sql = $this->original();
+        return $this->generatePostgresShowTableStatus(); 
+    }
+
+
+    /**
+     * Generates a PostgreSQL-compatible SQL query to mimic MySQL's "SHOW TABLE STATUS".
+     *
+     * @return string The generated SQL query
+     */
+    public function generatePostgresShowTableStatus($schema = "public")
+    {
+        $sql = <<<SQL
+        SELECT 
+            'Postgres' AS Engine,
+            cls.relname AS TableName, 
+            NULL AS Version,
+            NULL AS Row_format,
+            cls.reltuples AS Rows,
+            NULL AS Avg_row_length,
+            pg_relation_size(cls.oid) AS Data_length,
+            NULL AS Max_data_length,
+            pg_indexes_size(cls.oid) AS Index_length, 
+            NULL AS Data_free,
+            NULL AS Auto_increment,
+            NULL AS Create_time,
+            NULL AS Update_time,
+            NULL AS Check_time,
+            'UTF8' AS Table_collation,
+            NULL AS Checksum,
+            NULL AS Create_options,
+            obj_description(cls.oid) AS Comment
+        FROM
+            pg_class cls
+        JOIN 
+            pg_namespace nsp ON cls.relnamespace = nsp.oid
+        WHERE 
+            cls.relkind = 'r' 
+            AND nsp.nspname NOT LIKE 'pg_%' -- Ignore schemas with names starting with pg_
+            AND nsp.nspname != 'information_schema' -- Ignore the information_schema
+            AND nsp.nspname = $schema -- Select only tables in the 'myschema' schema
+        ORDER BY 
+            cls.relname ASC;
+        SQL;
+
+        return $sql;
+    }
+}