Multiple optimizations that try to preserve or infer the zero-terminated

property of TEXT values.  Avoid unnecessary copying of text values destined
to become function parameters.  All changes help improve performance of
doing UPDATEs on large JSON values that are indexed multiple ways.

FossilOrigin-Name: d0278cdedfa04fb0b61838ab9622be8a2c462f58d5c3ebc4c5f802a727d0974e

manifest

@@ -1,5 +1,5 @@
-C Performance\senhancements\sto\sthe\sJSON\sparser\sand\scode\sgenerator.
-D 2023-07-19T23:02:45.962
+C Multiple\soptimizations\sthat\stry\sto\spreserve\sor\sinfer\sthe\szero-terminated\nproperty\sof\sTEXT\svalues.\s\sAvoid\sunnecessary\scopying\sof\stext\svalues\sdestined\nto\sbecome\sfunction\sparameters.\s\sAll\schanges\shelp\simprove\sperformance\sof\ndoing\sUPDATEs\son\slarge\sJSON\svalues\sthat\sare\sindexed\smultiple\sways.
+D 2023-07-21T15:01:53.046
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -587,7 +587,7 @@ F src/date.c f73f203b3877cef866c60ab402aec2bf89597219b60635cf50cbe3c5e4533e94
 F src/dbpage.c f3eea5f7ec47e09ee7da40f42b25092ecbe961fc59566b8e5f705f34335b2387
 F src/dbstat.c ec92074baa61d883de58c945162d9e666c13cd7cf3a23bc38b4d1c4d0b2c2bef
 F src/delete.c cd5f5cd06ed0b6a882ec1a8c2a0d73b3cecb28479ad19e9931c4706c5e2182be
-F src/expr.c 8d1656b65e26af3e34f78e947ac423f0d20c214ed25a67486e433bf16ca6b543
+F src/expr.c ef4a81822da6f767696bd7f4b9983328af061158958138540142285a5b1181b7
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c a7fcbf7e66d14dbb73cf49f31489ebf66d0e6006c62b95246924a3bae9f37b36
 F src/func.c 25f2e0204c011be56fc3c9a180534b68ca4866c61ec19806880136450434112d
@@ -597,7 +597,7 @@ F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
 F src/hwtime.h f9c2dfb84dce7acf95ce6d289e46f5f9d3d1afd328e53da8f8e9008e3b3caae6
 F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
 F src/insert.c 3f0a94082d978bbdd33c38fefea15346c6c6bffb70bc645a71dc0f1f87dd3276
-F src/json.c e48136fce64e5004b1b8be76624cc9a4ac9ff6ae630a97df187c0ea4b9692d1b
+F src/json.c 2bf3223892b4b9be39d701a5d349efcce5f5eebf71baaf91ba5866e10127e839
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 176d6b2cb18a6ad73b133db17f6fc351c4d9a2d510deebdb76c22bde9cfd1465
 F src/main.c 512b1d45bc556edf4471a845afb7ba79e64bd5b832ab222dc195c469534cd002
@@ -707,10 +707,10 @@ F src/upsert.c 5303dc6c518fa7d4b280ec65170f465c7a70b7ac2b22491598f6d0b4875b3145
 F src/utf.c ee39565f0843775cc2c81135751ddd93eceb91a673ea2c57f61c76f288b041a0
 F src/util.c fea6fffdee3cdae917a66b70deec59d4f238057cfd6de623d15cf990c196940d
 F src/vacuum.c 604fcdaebe76f3497c855afcbf91b8fa5046b32de3045bab89cc008d68e40104
-F src/vdbe.c 74282a947234513872a83b0bab1b8c644ece64b3e27b053ef17677c8ff9c81e0
+F src/vdbe.c 4cda877d413a18fa07346b08d6959b3d18ce982357921e7acb9649fca2534a12
 F src/vdbe.h 41485521f68e9437fdb7ec4a90f9d86ab294e9bb8281e33b235915e29122cfc0
 F src/vdbeInt.h 7bd49eef8f89c1a271fbf12d80a206bf56c876814c5fc6bee340f4e1907095ae
-F src/vdbeapi.c de9703f8705afc393cc2864669ce28cf9516983c8331d59aa2b978de01634365
+F src/vdbeapi.c 1b17d1a53c3b88eb8bf2534f4f3557957f59f9431e5283734452b191cd45898d
 F src/vdbeaux.c b5e3f7e158518b4eca6f166ac43900640a3fe9735c710e12bfa119af21059339
 F src/vdbeblob.c 2516697b3ee8154eb8915f29466fb5d4f1ae39ee8b755ea909cefaf57ec5e2ce
 F src/vdbemem.c cf4a1556dd5b18c071cf7c243373c29ce752eb516022e3ad49ba72f08b785033
@@ -2043,8 +2043,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P bee9e403ae47103938aabb9a7a7e120dfa741b464875965e58788a51fa56a8fe 144c8ccf6e5bb2527dd98742f0d67e0a16c627e7c67f754ce8ed4c4fb5b8d8b6
-R af54725f832c177294e9e511cdacd53d
+P 0a745897d66e9f36ea6e787fad54f0c413d52c226dc96fad36ccd33a0aa1930e
+R ad6898efbc6819851ab380be79271f0e
 U drh
-Z 1c679f829efc53f4f55993e30939aa14
+Z ecdcb9c56dec3594bcd0055088d236ad
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-0a745897d66e9f36ea6e787fad54f0c413d52c226dc96fad36ccd33a0aa1930e
+d0278cdedfa04fb0b61838ab9622be8a2c462f58d5c3ebc4c5f802a727d0974e

src/expr.c

@@ -4690,8 +4690,7 @@ expr_code_doover:
           }
         }
 
-        sqlite3ExprCodeExprList(pParse, pFarg, r1, 0,
-                                SQLITE_ECEL_DUP|SQLITE_ECEL_FACTOR);
+        sqlite3ExprCodeExprList(pParse, pFarg, r1, 0, SQLITE_ECEL_FACTOR);
       }else{
         r1 = 0;
       }

src/json.c

@@ -501,7 +501,8 @@ static void jsonAppendValue(
 */
 static void jsonResult(JsonString *p){
   if( p->bErr==0 ){
-    sqlite3_result_text64(p->pCtx, p->zBuf, p->nUsed, 
+    if( p->nAlloc>=p->nUsed+1 ) p->zBuf[p->nUsed] = 0;
+    sqlite3_result_text64(p->pCtx, p->zBuf, p->nUsed,
                           p->bStatic ? SQLITE_TRANSIENT : sqlite3_free,
                           SQLITE_UTF8);
     jsonZero(p);

src/vdbe.c

@@ -556,6 +556,9 @@ void sqlite3VdbeMemPrettyPrint(Mem *pMem, StrAccum *pStr){
       sqlite3_str_appendchar(pStr, 1, (c>=0x20&&c<=0x7f) ? c : '.');
     }
     sqlite3_str_appendf(pStr, "]%s", encnames[pMem->enc]);
+    if( f & MEM_Term ){
+      sqlite3_str_appendf(pStr, "(0-term)");
+    }
   }
 }
 #endif
@@ -3085,6 +3088,9 @@ op_column_restart:
       rc = sqlite3VdbeMemFromBtree(pC->uc.pCursor, aOffset[p2], len, pDest);
       if( rc!=SQLITE_OK ) goto abort_due_to_error;
       sqlite3VdbeSerialGet((const u8*)pDest->z, t, pDest);
+      if( (t&1)!=0 && encoding==SQLITE_UTF8 ){
+        pDest->flags |= MEM_Term;
+      }
       pDest->flags &= ~MEM_Ephem;
     }
   }

src/vdbeapi.c

@@ -514,6 +514,15 @@ void sqlite3_result_text64(
     (void)invokeValueDestructor(z, xDel, pCtx);
   }else{
     setResultStrOrError(pCtx, z, (int)n, enc, xDel);
+    if( xDel==sqlite3_free && enc==SQLITE_UTF8 ){
+      Mem *pOut = pCtx->pOut;
+      if( pOut->z==z 
+       && sqlite3_msize(pOut->z)>=pOut->n+1
+       && pOut->z[n]==0
+      ){
+        pOut->flags |= MEM_Term;
+      }
+    }
   }
 }
 #ifndef SQLITE_OMIT_UTF16