refactor: Remove mcp-catalog_path variable and hardcode catalog path

Remove the mcp-catalog_path configuration variable and hardcode the catalog
database path to datadir/mcp_catalog.db for stability.

Rationale: The catalog database is session state, not user configuration.
Runtime swapping of the catalog could cause tables to be missed and the
catalog to fail even if it was succeeding a second earlier.

Changes:
- Removed catalog_path from mcp_thread_variables_names array
- Removed mcp_catalog_path from MCP_Thread variables struct
- Removed getter/setter logic for catalog_path
- Hardcoded catalog path to GloVars.datadir/mcp_catalog.db in:
  - ProxySQL_MCP_Server.cpp (Query_Tool_Handler initialization)
  - Admin_FlushVariables.cpp (MySQL_Tool_Handler reinitialization)
- Updated VARIABLES.md to document the hardcoded path
- Updated configure_mcp.sh to remove catalog_path configuration
- Updated MCP README to remove catalog_path references

doc/MCP/VARIABLES.md

@@ -175,16 +175,11 @@ The MySQL Tool Handler provides LLM-based tools for MySQL database exploration,
 
 ### Catalog Configuration
 
-#### `mcp-catalog_path`
-- **Type:** String (file path)
-- **Default:** `"mcp_catalog.db"`
-- **Description:** Path to the SQLite catalog database (relative to ProxySQL datadir)
-- **Runtime:** Yes
-- **Example:**
-  ```sql
-  SET mcp-catalog_path='/path/to/mcp_catalog.db';
-  LOAD MCP VARIABLES TO RUNTIME;
-  ```
+The catalog database path is **hardcoded** to `mcp_catalog.db` in the ProxySQL datadir and cannot be changed at runtime. The catalog stores:
+- Database schemas discovered during two-phase discovery
+- LLM memories (summaries, domains, metrics)
+- Tool usage statistics
+- Search history
 
 ## Management Commands
 

include/MCP_Thread.h

@@ -55,7 +55,7 @@ public:
 		char* mcp_mysql_user;                   ///< MySQL username for tool connections
 		char* mcp_mysql_password;               ///< MySQL password for tool connections
 		char* mcp_mysql_schema;                 ///< Default schema/database
-		char* mcp_catalog_path;                 ///< Path to catalog SQLite database
+		// Catalog path is hardcoded to mcp_catalog.db in the datadir
 	} variables;
 
 	/**

lib/Admin_FlushVariables.cpp

@@ -1538,13 +1538,17 @@ void ProxySQL_Admin::flush_mcp_variables___runtime_to_database(SQLite3DB* db, bo
 
 				// Create new tool handler with current configuration
 				proxy_info("MCP: Reinitializing MySQL Tool Handler with current configuration\n");
+
+				// Hardcode catalog path to datadir/mcp_catalog.db for stability
+				std::string catalog_path = std::string(GloVars.datadir) + "/mcp_catalog.db";
+
 				GloMCPH->mysql_tool_handler = new MySQL_Tool_Handler(
 					GloMCPH->variables.mcp_mysql_hosts ? GloMCPH->variables.mcp_mysql_hosts : "",
 					GloMCPH->variables.mcp_mysql_ports ? GloMCPH->variables.mcp_mysql_ports : "",
 					GloMCPH->variables.mcp_mysql_user ? GloMCPH->variables.mcp_mysql_user : "",
 					GloMCPH->variables.mcp_mysql_password ? GloMCPH->variables.mcp_mysql_password : "",
 					GloMCPH->variables.mcp_mysql_schema ? GloMCPH->variables.mcp_mysql_schema : "",
-					GloMCPH->variables.mcp_catalog_path ? GloMCPH->variables.mcp_catalog_path : ""
+					catalog_path.c_str()
 				);
 
 				if (GloMCPH->mysql_tool_handler->init() != 0) {

lib/MCP_Thread.cpp

@@ -29,7 +29,6 @@ static const char* mcp_thread_variables_names[] = {
 	"mysql_user",
 	"mysql_password",
 	"mysql_schema",
-	"catalog_path",
 	NULL
 };
 
@@ -54,7 +53,6 @@ MCP_Threads_Handler::MCP_Threads_Handler() {
 	variables.mcp_mysql_user = strdup("");
 	variables.mcp_mysql_password = strdup("");
 	variables.mcp_mysql_schema = strdup("");
-	variables.mcp_catalog_path = strdup("mcp_catalog.db");
 
 	status_variables.total_requests = 0;
 	status_variables.failed_requests = 0;
@@ -93,8 +91,6 @@ MCP_Threads_Handler::~MCP_Threads_Handler() {
 		free(variables.mcp_mysql_password);
 	if (variables.mcp_mysql_schema)
 		free(variables.mcp_mysql_schema);
-	if (variables.mcp_catalog_path)
-		free(variables.mcp_catalog_path);
 
 	if (mcp_server) {
 		delete mcp_server;
@@ -216,10 +212,6 @@ int MCP_Threads_Handler::get_variable(const char* name, char* val) {
 		sprintf(val, "%s", variables.mcp_mysql_schema ? variables.mcp_mysql_schema : "");
 		return 0;
 	}
-	if (!strcmp(name, "catalog_path")) {
-		sprintf(val, "%s", variables.mcp_catalog_path ? variables.mcp_catalog_path : "");
-		return 0;
-	}
 
 	return -1;
 }
@@ -316,12 +308,6 @@ int MCP_Threads_Handler::set_variable(const char* name, const char* value) {
 		variables.mcp_mysql_schema = strdup(value);
 		return 0;
 	}
-	if (!strcmp(name, "catalog_path")) {
-		if (variables.mcp_catalog_path)
-			free(variables.mcp_catalog_path);
-		variables.mcp_catalog_path = strdup(value);
-		return 0;
-	}
 
 	return -1;
 }

lib/ProxySQL_MCP_Server.cpp

@@ -76,13 +76,17 @@ ProxySQL_MCP_Server::ProxySQL_MCP_Server(int p, MCP_Threads_Handler* h)
 
 	// 2. Query Tool Handler (uses Discovery_Schema directly for two-phase discovery)
 	proxy_info("Initializing Query Tool Handler...\n");
+
+	// Hardcode catalog path to datadir/mcp_catalog.db for stability
+	std::string catalog_path = std::string(GloVars.datadir) + "/mcp_catalog.db";
+
 	handler->query_tool_handler = new Query_Tool_Handler(
 		handler->variables.mcp_mysql_hosts ? handler->variables.mcp_mysql_hosts : "",
 		handler->variables.mcp_mysql_ports ? handler->variables.mcp_mysql_ports : "",
 		handler->variables.mcp_mysql_user ? handler->variables.mcp_mysql_user : "",
 		handler->variables.mcp_mysql_password ? handler->variables.mcp_mysql_password : "",
 		handler->variables.mcp_mysql_schema ? handler->variables.mcp_mysql_schema : "",
-		handler->variables.mcp_catalog_path ? handler->variables.mcp_catalog_path : "mcp_catalog.db"
+		catalog_path.c_str()
 	);
 	if (handler->query_tool_handler->init() == 0) {
 		proxy_info("Query Tool Handler initialized successfully\n");

scripts/mcp/README.md

@@ -104,11 +104,6 @@ MCP (Model Context Protocol) is a JSON-RPC 2.0 protocol that allows AI/LLM appli
 | `mcp-mysql_hosts` | 127.0.0.1 | MySQL server(s) for tool execution |
 | `mcp-mysql_ports` | 3306 | MySQL port(s) |
 | `mcp-mysql_user` | (empty) | MySQL username for connections |
-| `mcp-mysql_password` | (empty) | MySQL password |
-| `mcp-mysql_schema` | (empty) | Default schema for queries |
-| `mcp-catalog_path` | mcp_catalog.db | SQLite catalog database path (relative to datadir) |
-
-**Endpoints:**
 - `POST https://localhost:6071/config` - Initialize, ping, tools/list
 - `POST https://localhost:6071/query` - Execute tools (tools/call)
 
@@ -545,7 +540,6 @@ MySQL Tool Handler initialized for schema 'testdb'
 | `mcp-mysql_user` | (empty) | MySQL username |
 | `mcp-mysql_password` | (empty) | MySQL password |
 | `mcp-mysql_schema` | (empty) | Default schema |
-| `mcp-catalog_path` | mcp_catalog.db | Catalog database path (relative to datadir) |
 
 ---
 

scripts/mcp/configure_mcp.sh

@@ -113,7 +113,6 @@ configure_mcp() {
     exec_admin_silent "SET mcp-mysql_user='${MYSQL_USER}';" || { log_error "Failed to set mcp-mysql_user"; errors=$((errors + 1)); }
     exec_admin_silent "SET mcp-mysql_password='${MYSQL_PASSWORD}';" || { log_error "Failed to set mcp-mysql_password"; errors=$((errors + 1)); }
     exec_admin_silent "SET mcp-mysql_schema='${MYSQL_DATABASE}';" || { log_error "Failed to set mcp-mysql_schema"; errors=$((errors + 1)); }
-    exec_admin_silent "SET mcp-catalog_path='mcp_catalog.db';" || { log_error "Failed to set mcp-catalog_path"; errors=$((errors + 1)); }
     exec_admin_silent "SET mcp-port='${MCP_PORT}';" || { log_error "Failed to set mcp-port"; errors=$((errors + 1)); }
     exec_admin_silent "SET mcp-enabled='${enable}';" || { log_error "Failed to set mcp-enabled"; errors=$((errors + 1)); }
 
@@ -128,7 +127,6 @@ configure_mcp() {
     echo "  mcp-mysql_user      = ${MYSQL_USER}"
     echo "  mcp-mysql_password  = ${MYSQL_PASSWORD}"
     echo "  mcp-mysql_schema    = ${MYSQL_DATABASE}"
-    echo "  mcp-catalog_path    = mcp_catalog.db (relative to datadir)"
     echo "  mcp-port            = ${MCP_PORT}"
     echo "  mcp-enabled         = ${enable}"
 }