Optimize sqlite3.oo1.DB.exec() for the rowMode='object' case to avoid converting the object property keys (column names) from native code to JS for each row. This speeds up large data sets considerably and addresses the report in [forum:3632183d2470617d|forum post 3632183d2470617d].

FossilOrigin-Name: 8b41ef8690001eb299f5b7182c28f5318333bff5b505e1d59d6e6f4556b1c759

3 files changed, 64 insertions, 44 deletions

diff --git a/ext/wasm/api/sqlite3-api-oo1.js b/ext/wasm/api/sqlite3-api-oo1.js
index 160d59db5..425b52eec 100644
--- a/ext/wasm/api/sqlite3-api-oo1.js
+++ b/ext/wasm/api/sqlite3-api-oo1.js
@@ -433,40 +433,56 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
       out.returnVal = ()=>opt.resultRows;
     }
     if(opt.callback || opt.resultRows){
-      switch((undefined===opt.rowMode)
-             ? 'array' : opt.rowMode) {
-          case 'object': out.cbArg = (stmt)=>stmt.get(Object.create(null)); break;
-          case 'array': out.cbArg = (stmt)=>stmt.get([]); break;
-          case 'stmt':
-            if(Array.isArray(opt.resultRows)){
-              toss3("exec(): invalid rowMode for a resultRows array: must",
-                    "be one of 'array', 'object',",
-                    "a result column number, or column name reference.");
-            }
-            out.cbArg = (stmt)=>stmt;
+      switch((undefined===opt.rowMode) ? 'array' : opt.rowMode) {
+        case 'object':
+          out.cbArg = (stmt,cache)=>{
+            if( !cache.columnNames ) cache.columnNames = stmt.getColumnNames([]);
+            /* https://sqlite.org/forum/forumpost/3632183d2470617d:
+               conversion of rows to objects (key/val pairs) is
+               somewhat expensive for large data sets because of the
+               native-to-JS conversion of the column names. If we
+               instead cache the names and build objects from that
+               list of strings, it can run twice as fast. The
+               difference is not noticeable for small data sets but
+               becomes human-perceivable when enough rows are
+               involved. */
+            const row = stmt.get([]);
+            const rv = Object.create(null);
+            for( const i in cache.columnNames ) rv[cache.columnNames[i]] = row[i];
+            return rv;
+          };
+          break;
+        case 'array': out.cbArg = (stmt)=>stmt.get([]); break;
+        case 'stmt':
+          if(Array.isArray(opt.resultRows)){
+            toss3("exec(): invalid rowMode for a resultRows array: must",
+                  "be one of 'array', 'object',",
+                  "a result column number, or column name reference.");
+          }
+          out.cbArg = (stmt)=>stmt;
+          break;
+        default:
+          if(util.isInt32(opt.rowMode)){
+            out.cbArg = (stmt)=>stmt.get(opt.rowMode);
             break;
-          default:
-            if(util.isInt32(opt.rowMode)){
-              out.cbArg = (stmt)=>stmt.get(opt.rowMode);
-              break;
-            }else if('string'===typeof opt.rowMode
-                     && opt.rowMode.length>1
-                     && '$'===opt.rowMode[0]){
-              /* "$X": fetch column named "X" (case-sensitive!). Prior
-                 to 2022-12-14 ":X" and "@X" were also permitted, but
-                 having so many options is unnecessary and likely to
-                 cause confusion. */
-              const $colName = opt.rowMode.substr(1);
-              out.cbArg = (stmt)=>{
-                const rc = stmt.get(Object.create(null))[$colName];
-                return (undefined===rc)
-                  ? toss3(capi.SQLITE_NOTFOUND,
-                          "exec(): unknown result column:",$colName)
-                  : rc;
-              };
-              break;
-            }
-            toss3("Invalid rowMode:",opt.rowMode);
+          }else if('string'===typeof opt.rowMode
+                   && opt.rowMode.length>1
+                   && '$'===opt.rowMode[0]){
+            /* "$X": fetch column named "X" (case-sensitive!). Prior
+               to 2022-12-14 ":X" and "@X" were also permitted, but
+               having so many options is unnecessary and likely to
+               cause confusion. */
+            const $colName = opt.rowMode.substr(1);
+            out.cbArg = (stmt)=>{
+              const rc = stmt.get(Object.create(null))[$colName];
+              return (undefined===rc)
+                ? toss3(capi.SQLITE_NOTFOUND,
+                        "exec(): unknown result column:",$colName)
+                : rc;
+            };
+            break;
+          }
+          toss3("Invalid rowMode:",opt.rowMode);
       }
     }
     return out;
@@ -884,10 +900,15 @@ globalThis.sqlite3ApiBootstrap.initializers.push(function(sqlite3){
                  and names. */) ? 0 : 1;
             evalFirstResult = false;
             if(arg.cbArg || resultRows){
+              const cbArgCache = Object.create(null)
+              /* 2nd arg for arg.cbArg, used by (at least) row-to-object
+                 converter */;
               for(; stmt.step(); stmt._lockedByExec = false){
-                if(0===gotColNames++) stmt.getColumnNames(opt.columnNames);
+                if(0===gotColNames++){
+                  stmt.getColumnNames(cbArgCache.columnNames = (opt.columnNames || []));
+                }
                 stmt._lockedByExec = true;
-                const row = arg.cbArg(stmt);
+                const row = arg.cbArg(stmt,cbArgCache);
                 if(resultRows) resultRows.push(row);
                 if(callback && false === callback.call(opt, row, stmt)){
                   break;
diff --git a/manifest b/manifest
index e296c3624..457e113cf 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sthe\s"interstage-heuristic"\sthat\sattempts\sto\savoid\swildly\sinefficient\nqueries\sthat\suse\stable\sscans\sinstead\sof\sindex\slookups\sbecause\sthe\soutput\nrow\sestimates\sare\sinaccurate.
-D 2024-04-04T14:26:42.961
+C Optimize\ssqlite3.oo1.DB.exec()\sfor\sthe\srowMode='object'\scase\sto\savoid\sconverting\sthe\sobject\sproperty\skeys\s(column\snames)\sfrom\snative\scode\sto\sJS\sfor\seach\srow.\sThis\sspeeds\sup\slarge\sdata\ssets\sconsiderably\sand\saddresses\sthe\sreport\sin\s[forum:3632183d2470617d|forum\spost\s3632183d2470617d].
+D 2024-04-04T22:53:09.385
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -606,7 +606,7 @@ F ext/wasm/api/post-js-header.js 04dc12c3edd666b64a1b4ef3b6690c88dcc653f26451fd4
 F ext/wasm/api/pre-js.c-pp.js ad906703f7429590f2fbf5e6498513bf727a1a4f0ebfa057afb08161d7511219
 F ext/wasm/api/sqlite3-api-cleanup.js d235ad237df6954145404305040991c72ef8b1881715d2a650dda7b3c2576d0e
 F ext/wasm/api/sqlite3-api-glue.js 2d35660c52dcb4bb16d00c56553d34e7caa6ad30083938b515e6f9aa0b312fbb
-F ext/wasm/api/sqlite3-api-oo1.js 7f3bcf0549ac44cde4b9da0b642d771916738d3f6781fb8a1757c50a91e506c0
+F ext/wasm/api/sqlite3-api-oo1.js 365b3ae01a461dc974796823652ef1ecb1a9fac5df295ee1a78002cc77afb0d8
 F ext/wasm/api/sqlite3-api-prologue.js 93a72b07b2a5d964d2edc76a90b439ece49298bd7ba60a1c6ae5d4878213701e
 F ext/wasm/api/sqlite3-api-worker1.js 8d9c0562831f62218170a3373468d8a0b7a6503b5985e309b69bf71187b525cf
 F ext/wasm/api/sqlite3-license-version-header.js 0c807a421f0187e778dc1078f10d2994b915123c1223fe752b60afdcd1263f89
@@ -2184,9 +2184,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 797cda7ddcceb140330d58892c3e73d28df72b638df00fd48f07dfcba7706c5f 186dcae19e249db36de15f295999cff25063b54ee3d5d481cd2ba99b6d13148e
-R 869b12f296c2e2b0f215f1adb6cf5942
-T +closed 186dcae19e249db36de15f295999cff25063b54ee3d5d481cd2ba99b6d13148e
-U drh
-Z 93e4543ac83acbe7df90dc3896cd40af
+P 7bf49e2c54c9f6f336416f01c0e76aaf70f1e2f3fd612232e5a33ae5dabe0900
+R 32cab23d7481e1a388944c536dd694cd
+U stephan
+Z 96ae2cb4464d7637da1ca6fd97c9b197
 # Remove this line to create a well-formed Fossil manifest.
diff --git a/manifest.uuid b/manifest.uuid
index e59021c9b..4ea31d83a 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-7bf49e2c54c9f6f336416f01c0e76aaf70f1e2f3fd612232e5a33ae5dabe0900
\ No newline at end of file
+8b41ef8690001eb299f5b7182c28f5318333bff5b505e1d59d6e6f4556b1c759
\ No newline at end of file