Add cache parameter 'selects'

Documentation/Filters/Cache.md

@@ -227,6 +227,29 @@ cached_data=thread_specific
 Default is `shared`. See `max_count` and `max_size` what implication changing
 this setting to `thread_specific` has.
 
+#### `selects`
+
+An enumeration option specifying what approach the cache should take with
+respect to `SELECT` statements. The allowed values are:
+
+   * `assume_cacheable`: The cache can assume that all `SELECT` statements,
+     without exceptions, are cacheable.
+   * `verify_cacheable`: The cache can *not* assume that all `SELECT`
+     statements are cacheable, but must verify that.
+
+```
+select=assume_cacheable
+```
+
+Default is `verify_cacheable`. In this case, the `SELECT` statements will be
+parsed and only those that are safe for caching - e.g. do *not* call any
+non-cacheable functions or access any non-cacheable variables - will be
+subject to caching.
+
+If `assume_cacheable` is specified, then all `SELECT` statements are
+assumed to be cacheable and will be parsed *only* if some specific rule
+requires that.
+
 #### `debug`
 
 An integer value, using which the level of debug logging made by the cache

server/modules/filter/cache/cachefilter.cc

@@ -49,6 +49,8 @@ void cache_config_finish(CACHE_CONFIG& config)
     config.hard_ttl = 0;
     config.soft_ttl = 0;
     config.debug = 0;
+    config.thread_model = CACHE_THREAD_MODEL_MT;
+    config.selects = CACHE_SELECTS_VERIFY_CACHEABLE;
 }
 
 /**
@@ -107,13 +109,21 @@ bool cache_command_show(const MODULECMD_ARG* pArgs)
 //
 
 // Enumeration values for `cached_data`
-static const MXS_ENUM_VALUE cached_data_values[] =
+static const MXS_ENUM_VALUE parameter_cached_data_values[] =
 {
     {"shared",          CACHE_THREAD_MODEL_MT},
     {"thread_specific", CACHE_THREAD_MODEL_ST},
     {NULL}
 };
 
+// Enumeration values for `selects`
+static const MXS_ENUM_VALUE parameter_selects_values[] =
+{
+    {"assume_cacheable", CACHE_SELECTS_ASSUME_CACHEABLE},
+    {"verify_cacheable", CACHE_SELECTS_VERIFY_CACHEABLE},
+    {NULL}
+};
+
 extern "C" MXS_MODULE* MXS_CREATE_MODULE()
 {
     static modulecmd_arg_type_t show_argv[] =
@@ -194,7 +204,14 @@ extern "C" MXS_MODULE* MXS_CREATE_MODULE()
                 MXS_MODULE_PARAM_ENUM,
                 CACHE_DEFAULT_THREAD_MODEL,
                 MXS_MODULE_OPT_NONE,
-                cached_data_values
+                parameter_cached_data_values
+            },
+            {
+                "selects",
+                MXS_MODULE_PARAM_ENUM,
+                CACHE_DEFAULT_SELECTS,
+                MXS_MODULE_OPT_NONE,
+                parameter_selects_values
             },
             {MXS_END_MODULE_PARAMS}
         }
@@ -291,7 +308,10 @@ bool CacheFilter::process_params(char **pzOptions, MXS_CONFIG_PARAMETER *ppParam
     config.max_resultset_size = config_get_size(ppParams, "max_resultset_size");
     config.thread_model = static_cast<cache_thread_model_t>(config_get_enum(ppParams,
                                                                             "cached_data",
-                                                                            cached_data_values));
+                                                                            parameter_cached_data_values));
+    config.selects = static_cast<cache_selects_t>(config_get_enum(ppParams,
+                                                                  "selects",
+                                                                  parameter_selects_values));
 
     if (!config.storage)
     {

server/modules/filter/cache/cachefilter.h

@@ -54,6 +54,14 @@
 #define CACHE_DEFAULT_MAX_SIZE           "0"
 // Thread model
 #define CACHE_DEFAULT_THREAD_MODEL       "shared"
+// Cacheable selects
+#define CACHE_DEFAULT_SELECTS            "verify_cacheable"
+
+typedef enum cache_selects
+{
+    CACHE_SELECTS_ASSUME_CACHEABLE,
+    CACHE_SELECTS_VERIFY_CACHEABLE,
+} cache_selects_t;
 
 typedef struct cache_config
 {
@@ -70,4 +78,5 @@ typedef struct cache_config
     uint64_t max_size;                 /**< Maximum size of the cache.*/
     uint32_t debug;                    /**< Debug settings. */
     cache_thread_model_t thread_model; /**< Thread model. */
+    cache_selects_t selects;           /**< Assume/verify that selects are cacheable. */
 } CACHE_CONFIG;