Add the SQLITE_DB_STATUS_CACHE_HIT and MISS options. For querying the number of cache hits and misses on a per-connection basis.

FossilOrigin-Name: 5100b6e9dc5107f0f835d0aac26fe6d4938ffc73

5 files changed, 71 insertions, 8 deletions

diff --git a/src/pager.c b/src/pager.c
index f8d3ba998..99a3ebd4c 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -670,8 +670,8 @@ struct Pager {
   char *zJournal;             /* Name of the journal file */
   int (*xBusyHandler)(void*); /* Function to call when busy */
   void *pBusyHandlerArg;      /* Context argument for xBusyHandler */
+  int nHit, nMiss;            /* Total cache hits and misses */
 #ifdef SQLITE_TEST
-  int nHit, nMiss;            /* Cache hits and missing */
   int nRead, nWrite;          /* Database pages read/written */
 #endif
   void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */
@@ -4169,7 +4169,7 @@ static int pagerStress(void *p, PgHdr *pPg){
   **
   ** Spilling is also prohibited when in an error state since that could
   ** lead to database corruption.   In the current implementaton it 
-  ** is impossible for sqlite3PCacheFetch() to be called with createFlag==1
+  ** is impossible for sqlite3PcacheFetch() to be called with createFlag==1
   ** while in the error state, hence it is impossible for this routine to
   ** be called in the error state.  Nevertheless, we include a NEVER()
   ** test for the error state as a safeguard against future changes.
@@ -5005,14 +5005,13 @@ int sqlite3PagerAcquire(
     /* In this case the pcache already contains an initialized copy of
     ** the page. Return without further ado.  */
     assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) );
-    PAGER_INCR(pPager->nHit);
+    pPager->nHit++;
     return SQLITE_OK;
 
   }else{
     /* The pager cache has created a new page. Its content needs to 
     ** be initialized.  */
 
-    PAGER_INCR(pPager->nMiss);
     pPg = *ppPage;
     pPg->pPager = pPager;
 
@@ -5048,6 +5047,7 @@ int sqlite3PagerAcquire(
       IOTRACE(("ZERO %p %d\n", pPager, pgno));
     }else{
       assert( pPg->pPager==pPager );
+      pPager->nMiss++;
       rc = readDbPage(pPg);
       if( rc!=SQLITE_OK ){
         goto pager_acquire_err;
@@ -6083,6 +6083,31 @@ int *sqlite3PagerStats(Pager *pPager){
 #endif
 
 /*
+** Parameter eStat must be either SQLITE_DBSTATUS_CACHE_HIT or
+** SQLITE_DBSTATUS_CACHE_MISS. Before returning, *pnVal is incremented by the
+** current cache hit or miss count, according to the value of eStat. If the 
+** reset parameter is non-zero, the cache hit or miss count is zeroed before 
+** returning.
+*/
+void sqlite3PagerCacheStat(Pager *pPager, int eStat, int reset, int *pnVal){
+  int *piStat;
+
+  assert( eStat==SQLITE_DBSTATUS_CACHE_HIT
+       || eStat==SQLITE_DBSTATUS_CACHE_MISS
+  );
+  if( eStat==SQLITE_DBSTATUS_CACHE_HIT ){
+    piStat = &pPager->nHit;
+  }else{
+    piStat = &pPager->nMiss;
+  }
+
+  *pnVal += *piStat;
+  if( reset ){
+    *piStat = 0;
+  }
+}
+
+/*
 ** Return true if this is an in-memory pager.
 */
 int sqlite3PagerIsMemdb(Pager *pPager){
diff --git a/src/pager.h b/src/pager.h
index eab7ddaf8..540557248 100644
--- a/src/pager.h
+++ b/src/pager.h
@@ -155,6 +155,7 @@ const char *sqlite3PagerJournalname(Pager*);
 int sqlite3PagerNosync(Pager*);
 void *sqlite3PagerTempSpace(Pager*);
 int sqlite3PagerIsMemdb(Pager*);
+void sqlite3PagerCacheStat(Pager *, int, int, int *);
 
 /* Functions used to truncate the database file. */
 void sqlite3PagerTruncateImage(Pager*,Pgno);
diff --git a/src/sqlite.h.in b/src/sqlite.h.in
index ba5c20265..43694f5fa 100644
--- a/src/sqlite.h.in
+++ b/src/sqlite.h.in
@@ -5810,6 +5810,18 @@ int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
 ** the database connection.)^
 ** ^The highwater mark associated with SQLITE_DBSTATUS_STMT_USED is always 0.
 ** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_HIT]] ^(<dt>SQLITE_DBSTATUS_CACHE_HIT</dt>
+** <dd>This parameter returns the number of pager cache hits that have
+** occurred. ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_HIT 
+** is always 0.
+** </dd>
+**
+** [[SQLITE_DBSTATUS_CACHE_MISS]] ^(<dt>SQLITE_DBSTATUS_CACHE_MISS</dt>
+** <dd>This parameter returns the number of pager cache misses that have
+** occurred. ^The highwater mark associated with SQLITE_DBSTATUS_CACHE_MISS 
+** is always 0.
+** </dd>
 ** </dl>
 */
 #define SQLITE_DBSTATUS_LOOKASIDE_USED       0
@@ -5819,7 +5831,9 @@ int sqlite3_db_status(sqlite3*, int op, int *pCur, int *pHiwtr, int resetFlg);
 #define SQLITE_DBSTATUS_LOOKASIDE_HIT        4
 #define SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE  5
 #define SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL  6
-#define SQLITE_DBSTATUS_MAX                  6   /* Largest defined DBSTATUS */
+#define SQLITE_DBSTATUS_CACHE_HIT            7
+#define SQLITE_DBSTATUS_CACHE_MISS           8
+#define SQLITE_DBSTATUS_MAX                  8   /* Largest defined DBSTATUS */
 
 
 /*
@@ -5873,7 +5887,6 @@ int sqlite3_stmt_status(sqlite3_stmt*, int op,int resetFlg);
 ** A non-zero value in this counter may indicate an opportunity to
 ** improvement performance by adding permanent indices that do not
 ** need to be reinitialized each time the statement is run.</dd>
-**
 ** </dl>
 */
 #define SQLITE_STMTSTATUS_FULLSCAN_STEP     1
diff --git a/src/status.c b/src/status.c
index b8c1d58df..b23238bb1 100644
--- a/src/status.c
+++ b/src/status.c
@@ -218,6 +218,28 @@ int sqlite3_db_status(
       break;
     }
 
+    /*
+    ** Set *pCurrent to the total cache hits or misses encountered by all
+    ** pagers the database handle is connected to. *pHighwater is always set 
+    ** to zero.
+    */
+    case SQLITE_DBSTATUS_CACHE_HIT:
+    case SQLITE_DBSTATUS_CACHE_MISS: {
+      int i;
+      int nRet = 0;
+      assert( SQLITE_DBSTATUS_CACHE_MISS==SQLITE_DBSTATUS_CACHE_HIT+1 );
+
+      for(i=0; i<db->nDb; i++){
+        if( db->aDb[i].pBt ){
+          Pager *pPager = sqlite3BtreePager(db->aDb[i].pBt);
+          sqlite3PagerCacheStat(pPager, op, resetFlag, &nRet);
+        }
+      }
+      *pHighwater = 0;
+      *pCurrent = nRet;
+      break;
+    }
+
     default: {
       rc = SQLITE_ERROR;
     }
diff --git a/src/test_malloc.c b/src/test_malloc.c
index 46ec94d32..e955d5790 100644
--- a/src/test_malloc.c
+++ b/src/test_malloc.c
@@ -1325,11 +1325,13 @@ static int test_db_status(
     { "STMT_USED",           SQLITE_DBSTATUS_STMT_USED           },
     { "LOOKASIDE_HIT",       SQLITE_DBSTATUS_LOOKASIDE_HIT       },
     { "LOOKASIDE_MISS_SIZE", SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE },
-    { "LOOKASIDE_MISS_FULL", SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL }
+    { "LOOKASIDE_MISS_FULL", SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL },
+    { "CACHE_HIT",           SQLITE_DBSTATUS_CACHE_HIT           },
+    { "CACHE_MISS",          SQLITE_DBSTATUS_CACHE_MISS          }
   };
   Tcl_Obj *pResult;
   if( objc!=4 ){
-    Tcl_WrongNumArgs(interp, 1, objv, "PARAMETER RESETFLAG");
+    Tcl_WrongNumArgs(interp, 1, objv, "DB PARAMETER RESETFLAG");
     return TCL_ERROR;
   }
   if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;