Use relative catalog path instead of absolute path

- Change mcp-catalog_path default from /var/lib/proxysql/mcp_catalog.db to mcp_catalog.db
- SQLite accepts relative paths, which are resolved relative to the process working directory
- ProxySQL's working directory is its datadir, so the catalog will be stored there
- Update configure_mcp.sh to set mcp-catalog_path='mcp_catalog.db'
- Update lib/MCP_Thread.cpp default to "mcp_catalog.db"
- Update README.md to document relative path behavior

lib/MCP_Thread.cpp

@@ -49,7 +49,7 @@ 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("/var/lib/proxysql/mcp_catalog.db");
+	variables.mcp_catalog_path = strdup("mcp_catalog.db");
 
 	status_variables.total_requests = 0;
 	status_variables.failed_requests = 0;

scripts/mcp/README.md

@@ -106,7 +106,7 @@ MCP (Model Context Protocol) is a JSON-RPC 2.0 protocol that allows AI/LLM appli
 | `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` | /var/lib/proxysql/mcp_catalog.db | SQLite catalog database path |
+| `mcp-catalog_path` | mcp_catalog.db | SQLite catalog database path (relative to datadir) |
 
 **Endpoints:**
 - `POST https://localhost:6071/config` - Initialize, ping, tools/list
@@ -545,7 +545,7 @@ 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` | /var/lib/proxysql/mcp_catalog.db | Catalog database path |
+| `mcp-catalog_path` | mcp_catalog.db | Catalog database path (relative to datadir) |
 
 ---
 

scripts/mcp/configure_mcp.sh

@@ -105,7 +105,7 @@ SET mcp-mysql_ports='${MYSQL_PORT}';
 SET mcp-mysql_user='${MYSQL_USER}';
 SET mcp-mysql_password='${MYSQL_PASSWORD}';
 SET mcp-mysql_schema='${MYSQL_DATABASE}';
-SET mcp-catalog_path='/var/lib/proxysql/mcp_catalog.db';
+SET mcp-catalog_path='mcp_catalog.db';
 SET mcp-port='${MCP_PORT}';
 SET mcp-enabled='${enable}';
 EOF
@@ -116,7 +116,7 @@ EOF
     echo "  mcp-mysql_user      = ${MYSQL_USER}"
     echo "  mcp-mysql_password  = ${MYSQL_PASSWORD}"
     echo "  mcp-mysql_schema    = ${MYSQL_DATABASE}"
-    echo "  mcp-catalog_path    = /var/lib/proxysql/mcp_catalog.db"
+    echo "  mcp-catalog_path    = mcp_catalog.db (relative to datadir)"
     echo "  mcp-port            = ${MCP_PORT}"
     echo "  mcp-enabled         = ${enable}"
 }