JSON performance improvements: (1) Add a cache for large string values

on OP_Column to avoid having to extract the string multiple times.
(2) Internal JSON caching improvements.

FossilOrigin-Name: 771fe35074b50b8d4a6583e61c53871b2445f7a58c82f3fc3bf6776e562e63af

1 files changed, 50 insertions, 43 deletions

diff --git a/src/json.c b/src/json.c
index 493a1b99c..cc39264c0 100644
--- a/src/json.c
+++ b/src/json.c
@@ -174,6 +174,7 @@ struct JsonParse {
   u16 iDepth;        /* Nesting depth */
   u8 nErr;           /* Number of errors seen */
   u8 oom;            /* Set to true if out of memory */
+  u8 bJsonIsRCStr;   /* True if zJson is an RCStr */
   u8 hasNonstd;      /* True if input uses non-standard features like JSON5 */
   u8 useMod;         /* Actually use the edits contain inside aNode */
   u8 hasMod;         /* aNode contains edits from the original zJson */
@@ -619,6 +620,11 @@ static void jsonParseReset(JsonParse *pParse){
     sqlite3_free(pParse->aUp);
     pParse->aUp = 0;
   }
+  if( pParse->bJsonIsRCStr ){
+    sqlite3RCStrUnref(pParse->zJson);
+    pParse->zJson = 0;
+    pParse->bJsonIsRCStr = 0;
+  }
   if( pParse->zAlt ){
     sqlite3RCStrUnref(pParse->zAlt);
     pParse->zAlt = 0;
@@ -1745,26 +1751,15 @@ json_parse_restart:
 ** are any errors.  If an error occurs, free all memory held by pParse,
 ** but not pParse itself.
 **
-** pParse is uninitialized when this routine is called.
-**
-** pParse->nJPRef set to 1.  The caller becomes the owner of the
-** the JsonParse object.
-**
-** pParse->bOwnsJson is set to bTakeJson.  If bTakeJson is 1, the newly
-** initialized JsonParse object will become the owner of the zJson input
-** string.  If bTakeJson is 0, then the caller is responsible for
-** preserving zJson for the lifetime of the JsonParse object.
+** pParse must be initialized to an empty parse object prior to calling
+** this routine.
 */
 static int jsonParse(
   JsonParse *pParse,           /* Initialize and fill this JsonParse object */
-  sqlite3_context *pCtx,       /* Report errors here */
-  char *zJson                  /* Input JSON text to be parsed */
+  sqlite3_context *pCtx        /* Report errors here */
 ){
   int i;
-  memset(pParse, 0, sizeof(*pParse));
-  if( zJson==0 ) return 1;
-  pParse->zJson = zJson;
-  pParse->nJPRef = 1;
+  const char *zJson = pParse->zJson;
   i = jsonParseValue(pParse, 0);
   if( pParse->oom ) i = -1;
   if( i>0 ){
@@ -1884,6 +1879,7 @@ static JsonParse *jsonParseCached(
   int iMinKey = 0;
   u32 iMinHold = 0xffffffff;
   u32 iMaxHold = 0;
+  int bJsonRCStr;
 
   if( zJson==0 ) return 0;
   for(iKey=0; iKey<JSON_CACHE_SZ; iKey++){
@@ -1895,7 +1891,7 @@ static JsonParse *jsonParseCached(
     if( pMatch==0
      && p->nJson==nJson
      && (p->hasMod==0 || bUnedited==0)
-     && memcmp(p->zJson,zJson,nJson)==0
+     && (p->zJson==zJson || memcmp(p->zJson,zJson,nJson)==0)
     ){
       p->nErr = 0;
       p->useMod = 0;
@@ -1930,16 +1926,22 @@ static JsonParse *jsonParseCached(
   /* The input JSON was not found anywhere in the cache.  We will need
   ** to parse it ourselves and generate a new JsonParse object.
   */
-  p = sqlite3_malloc64( sizeof(*p) + nJson + 1 );
+  bJsonRCStr = sqlite3ValueIsOfClass(pJson,(void(*)(void*))sqlite3RCStrUnref);
+  p = sqlite3_malloc64( sizeof(*p) + (bJsonRCStr ? 0 : nJson+1) );
   if( p==0 ){
     sqlite3_result_error_nomem(pCtx);
     return 0;
   }
   memset(p, 0, sizeof(*p));
-  p->zJson = (char*)&p[1];
-  memcpy(p->zJson, zJson, nJson);
-  p->zJson[nJson] = 0;
-  if( jsonParse(p, pErrCtx, p->zJson) ){
+  if( bJsonRCStr ){
+    p->zJson = sqlite3RCStrRef(zJson);
+    p->bJsonIsRCStr = 1;
+  }else{
+    p->zJson = (char*)&p[1];
+    memcpy(p->zJson, zJson, nJson+1);
+  }
+  p->nJPRef = 1;
+  if( jsonParse(p, pErrCtx) ){
     if( pErrCtx==0 ){
       p->nErr = 1;
       assert( p->nJPRef==1 ); /* Caller will own the new JsonParse object p */
@@ -2663,29 +2665,27 @@ static void jsonPatchFunc(
   int argc,
   sqlite3_value **argv
 ){
-  JsonParse x;     /* The JSON that is being patched */
-  JsonParse y;     /* The patch */
+  JsonParse *pX;     /* The JSON that is being patched */
+  JsonParse *pY;     /* The patch */
   JsonNode *pResult;   /* The result of the merge */
 
   UNUSED_PARAMETER(argc);
-  if( jsonParse(&x, ctx, (char*)sqlite3_value_text(argv[0])) ) return;
-  if( jsonParse(&y, ctx, (char*)sqlite3_value_text(argv[1])) ){
-    jsonParseReset(&x);
-    return;
-  }
-  x.useMod = 1;
-  y.useMod = 1;
-  pResult = jsonMergePatch(&x, 0, y.aNode);
-  assert( pResult!=0 || x.oom );
-  if( pResult && x.oom==0 ){
-    jsonDebugPrintParse(&x);
+  pX = jsonParseCached(ctx, argv[0], ctx, 1);
+  if( pX==0 ) return;
+  pY = jsonParseCached(ctx, argv[1], ctx, 1);
+  if( pY==0 ) return;
+  pX->useMod = 1;
+  pX->hasMod = 1;
+  pY->useMod = 1;
+  pResult = jsonMergePatch(pX, 0, pY->aNode);
+  assert( pResult!=0 || pX->oom );
+  if( pResult && pX->oom==0 ){
+    jsonDebugPrintParse(pX);
     jsonDebugPrintNode(pResult);
-    jsonReturnJson(&x, pResult, ctx, 0);
+    jsonReturnJson(pX, pResult, ctx, 0);
   }else{
     sqlite3_result_error_nomem(ctx);
   }
-  jsonParseReset(&x);
-  jsonParseReset(&y);
 }
 
 
@@ -3312,7 +3312,6 @@ static int jsonEachOpenTree(sqlite3_vtab *p, sqlite3_vtab_cursor **ppCursor){
 /* Reset a JsonEachCursor back to its original state.  Free any memory
 ** held. */
 static void jsonEachCursorReset(JsonEachCursor *p){
-  sqlite3_free(p->zJson);
   sqlite3_free(p->zRoot);
   jsonParseReset(&p->sParse);
   p->iRowid = 0;
@@ -3632,11 +3631,19 @@ static int jsonEachFilter(
   if( idxNum==0 ) return SQLITE_OK;
   z = (const char*)sqlite3_value_text(argv[0]);
   if( z==0 ) return SQLITE_OK;
-  n = sqlite3_value_bytes(argv[0]);
-  p->zJson = sqlite3_malloc64( n+1 );
-  if( p->zJson==0 ) return SQLITE_NOMEM;
-  memcpy(p->zJson, z, (size_t)n+1);
-  if( jsonParse(&p->sParse, 0, p->zJson) ){
+  memset(&p->sParse, 0, sizeof(p->sParse));
+  p->sParse.nJPRef = 1;
+  if( sqlite3ValueIsOfClass(argv[0], (void(*)(void*))sqlite3RCStrUnref) ){
+    p->sParse.zJson = sqlite3RCStrRef((char*)z);
+  }else{
+    n = sqlite3_value_bytes(argv[0]);
+    p->sParse.zJson = sqlite3RCStrNew( n+1 );
+    if( p->sParse.zJson==0 ) return SQLITE_NOMEM;
+    memcpy(p->sParse.zJson, z, (size_t)n+1);
+  }
+  p->sParse.bJsonIsRCStr = 1;
+  p->zJson = p->sParse.zJson;
+  if( jsonParse(&p->sParse, 0) ){
     int rc = SQLITE_NOMEM;
     if( p->sParse.oom==0 ){
       sqlite3_free(cur->pVtab->zErrMsg);