From: drh <drh@noemail.net>
Date: Fri, 1 Jan 2021 20:04:34 +0000 (+0000)
Subject: Change the unions of the Table.addColOffset field from characters to bytes.
X-Git-Tag: version-3.35.0~151
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=37114fbfcc3b7e03ca9d4aa6c23d36e3df0ce553;p=thirdparty%2Fsqlite.git

Change the unions of the Table.addColOffset field from characters to bytes.
This makes the query that implements ALTER TABLE ADD COLUMN more complex and
slightly slower, but also makes CREATE TABLE statement parsing faster by
avoiding a call to sqlite3UtfCharLen().  Since, CREATE TABLE parsing is far
more common than ALTER TABLE, this is a net win for performance.

FossilOrigin-Name: 6f25f2529f1495a26129d7d407979906e4962b2de351f901d41cb037d05ba780
---

diff --git a/manifest b/manifest
index 1aca84feb2..7ea3b257e6 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Use\sthe\scolumn\sname\shash\sto\simprove\sperformance\sof\scolumn\sname\scollision\ndetection\swhile\sparsing\sCREATE\sTABLE\sstatements.
-D 2021-01-01T19:17:01.346
+C Change\sthe\sunions\sof\sthe\sTable.addColOffset\sfield\sfrom\scharacters\sto\sbytes.\nThis\smakes\sthe\squery\sthat\simplements\sALTER\sTABLE\sADD\sCOLUMN\smore\scomplex\sand\nslightly\sslower,\sbut\salso\smakes\sCREATE\sTABLE\sstatement\sparsing\sfaster\sby\navoiding\sa\scall\sto\ssqlite3UtfCharLen().\s\sSince,\sCREATE\sTABLE\sparsing\sis\sfar\nmore\scommon\sthan\sALTER\sTABLE,\sthis\sis\sa\snet\swin\sfor\sperformance.
+D 2021-01-01T20:04:34.680
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -474,7 +474,7 @@ F spec.template 86a4a43b99ebb3e75e6b9a735d5fd293a24e90ca
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 fc7ad8990fc8409983309bb80de8c811a7506786
 F sqlite3.pc.in 48fed132e7cb71ab676105d2a4dc77127d8c1f3a
-F src/alter.c b6de60d59419e34f5b48ff2b21fe0f9bb66fc714e5545a6ac790ac7a0c46548c
+F src/alter.c 36cae0d6e3e91a1996e1a472f8c7242c31a4e38ba4295e3056da198c04fd2a87
 F src/analyze.c 01c6c6765cb4d40b473b71d85535093730770bb186f2f473abac25f07fcdee5c
 F src/attach.c 0f497c15c4cfe3bdcb214f0dbdbbb6c5ed7e8a9308ac445c7959f5e5780437a9
 F src/auth.c 8d1df0e2ef8bafbedd4f1fe4baff03eb27507da4bf6e449df3613d383c4018b2
@@ -484,7 +484,7 @@ F src/btmutex.c 8acc2f464ee76324bf13310df5692a262b801808984c1b79defb2503bbafadb6
 F src/btree.c 0f9cb686871ae668817673f0823b55d1bcadbc86ea28bd22c590b064a8322d5a
 F src/btree.h 285f8377aa1353185a32bf455faafa9ff9a0d40d074d60509534d14990c7829e
 F src/btreeInt.h 7614cae30f95b6aed0c7cac7718276a55cfe2c77058cbfd8bef5b75329757331
-F src/build.c f5610708b09e6e2aed20e9f87e41abc9cb7d9c524b2af473b6b8f979185fcc3c
+F src/build.c 7a9983015d707482329820eb0ab6bc014554cbd89f8f0312e88ee47ca924257d
 F src/callback.c d0b853dd413255d2e337b34545e54d888ea02f20da5ad0e63585b389624c4a6c
 F src/complete.c a3634ab1e687055cd002e11b8f43eb75c17da23e
 F src/ctime.c 2a322b9a3d75771fb4d99e0702851f4f68dda982507a0f798eefb0712969a410
@@ -1895,7 +1895,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5ac939e0adc923378173297e934c3664254a4fefbcddcc842bf4cc42dbaacf4f
-R 76ed3eb5d9ad1369259443b69c6d4eb4
+P d02820f03575e4633a7917427f11c19f99bd7b92f37d0ffe6fdc2418ad729813
+R d65e8365f48ba6717e932860e31b53aa
 U drh
-Z 392a8d945c1dcd1bc8026b48aa7097cf
+Z 862f00eca17b025046c1fc8e371a884b
diff --git a/manifest.uuid b/manifest.uuid
index 7ce76aea34..377d6e125d 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-d02820f03575e4633a7917427f11c19f99bd7b92f37d0ffe6fdc2418ad729813
\ No newline at end of file
+6f25f2529f1495a26129d7d407979906e4962b2de351f901d41cb037d05ba780
\ No newline at end of file
diff --git a/src/alter.c b/src/alter.c
index f4098863dd..e0beb8f3ed 100644
--- a/src/alter.c
+++ b/src/alter.c
@@ -381,11 +381,14 @@ void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){
       *zEnd-- = '\0';
     }
     db->mDbFlags |= DBFLAG_PreferBuiltin;
+    /* substr() operations on characters, but addColOffset is in bytes. So we
+    ** have to use printf() to translate between these units: */
     sqlite3NestedParse(pParse, 
         "UPDATE \"%w\"." DFLT_SCHEMA_TABLE " SET "
-          "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "
+          "sql = printf('%%.%ds, ',sql) || %Q"
+          " || substr(sql,1+length(printf('%%.%ds',sql))) "
         "WHERE type = 'table' AND name = %Q", 
-      zDb, pNew->addColOffset, zCol, pNew->addColOffset+1,
+      zDb, pNew->addColOffset, zCol, pNew->addColOffset,
       zTab
     );
     sqlite3DbFree(db, zCol);
diff --git a/src/build.c b/src/build.c
index 3a35530400..c9877951c6 100644
--- a/src/build.c
+++ b/src/build.c
@@ -2564,7 +2564,7 @@ void sqlite3EndTable(
         pCons = pEnd;
       }
       nName = (int)((const char *)pCons->z - zName);
-      p->addColOffset = 13 + sqlite3Utf8CharLen(zName, nName);
+      p->addColOffset = 13 + nName;
     }
 #endif
   }