From 69f6e2587bef21d7faa3f11748529ac8b96f8641 Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Mon, 11 Jan 2016 18:05:00 +0000
Subject: [PATCH] Performance optimization on the Column opcode.

FossilOrigin-Name: ecc98bef43c2fd07d64e4efddf340929a875ebac
---
 manifest      | 12 ++++++------
 manifest.uuid |  2 +-
 src/vdbe.c    | 54 ++++++++++++++++++++++++++-------------------------
 3 files changed, 35 insertions(+), 33 deletions(-)

diff --git a/manifest b/manifest
index 7c3ae97b20..e4dfdc13fc 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Performance\soptimization\sin\ssqlite3WalkExpr().
-D 2016-01-11T14:19:14.339
+C Performance\soptimization\son\sthe\sColumn\sopcode.
+D 2016-01-11T18:05:00.482
 F Makefile.in 7c8cc4c2f0179efc6fa9492141d1fb65f4807054
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc e45d8b9b56dfa3f2cd860b2c28bd9d304513b042
@@ -398,7 +398,7 @@ F src/update.c 17332f9fe818cbc0444c36a811800af8498af4c3
 F src/utf.c 32d7f82aa921322f3e1c956f4b58f019ebd2c6b3
 F src/util.c e802e8e311a0d6c48cd1b3e89db164f6f0248d70
 F src/vacuum.c 2ddd5cad2a7b9cef7f9e431b8c7771634c6b1701
-F src/vdbe.c 6ac8e5d808d48afc369316e147c191102f0584c1
+F src/vdbe.c 6572d00eefeaa0b14b325fdf3a409920ec3fee82
 F src/vdbe.h efb7a8c1459e31f3ea4377824c6a7e4cb5068637
 F src/vdbeInt.h 42eefa4f9e7432b9968d321b44e48821ec13b189
 F src/vdbeapi.c 020681b943e77766b32ae1cddf86d7831b7374ca
@@ -1407,7 +1407,7 @@ F tool/vdbe_profile.tcl 246d0da094856d72d2c12efec03250d71639d19f
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 8e807bfaa197027d0cb73532baa96755ce71ea12
-R 177e5551beb5399a29df920e18a04961
+P 2f8bd5fab8cc51d1f8932c3490fd24dbccf6ef31
+R 68508ce4367c0efdf38feafa98972c4a
 U drh
-Z b8d12fcc18213355136dacd10d5cf924
+Z e90441a49428aea3c83069305613bb8e
diff --git a/manifest.uuid b/manifest.uuid
index 1f83d937d4..bccf8bb6b0 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-2f8bd5fab8cc51d1f8932c3490fd24dbccf6ef31
\ No newline at end of file
+ecc98bef43c2fd07d64e4efddf340929a875ebac
\ No newline at end of file
diff --git a/src/vdbe.c b/src/vdbe.c
index 5acb3b3137..7eb4c0baeb 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -2374,7 +2374,6 @@ case OP_Column: {
   u64 offset64;      /* 64-bit offset */
   u32 avail;         /* Number of bytes of available data */
   u32 t;             /* A type code from the record header */
-  u16 fx;            /* pDest->flags value */
   Mem *pReg;         /* PseudoTable input register */
 
   p2 = pOp->p2;
@@ -2552,10 +2551,31 @@ case OP_Column: {
   assert( sqlite3VdbeCheckMemInvariants(pDest) );
   if( VdbeMemDynamic(pDest) ) sqlite3VdbeMemSetNull(pDest);
   assert( t==pC->aType[p2] );
+  pDest->enc = encoding;
   if( pC->szRow>=aOffset[p2+1] ){
     /* This is the common case where the desired content fits on the original
     ** page - where the content is not on an overflow page */
-    sqlite3VdbeSerialGet(pC->aRow+aOffset[p2], t, pDest);
+    zData = pC->aRow + aOffset[p2];
+    if( t<12 ){
+      sqlite3VdbeSerialGet(zData, t, pDest);
+    }else{
+      /* If the column value is a string, we need a persistent value, not
+      ** a MEM_Ephem value.  This branch is a fast short-cut that is equivalent
+      ** to calling sqlite3VdbeSerialGet() and sqlite3VdbeDeephemeralize().
+      */
+      static const u16 aFlag[] = { MEM_Blob, MEM_Str|MEM_Term };
+      pDest->n = len = (t-12)/2;
+      if( pDest->szMalloc < len+2 ){
+        pDest->flags = MEM_Null;
+        if( sqlite3VdbeMemGrow(pDest, len+2, 0) ) goto no_mem;
+      }else{
+        pDest->z = pDest->zMalloc;
+      }
+      memcpy(pDest->z, zData, len);
+      pDest->z[len] = 0;
+      pDest->z[len+1] = 0;
+      pDest->flags = aFlag[t&1];
+    }
   }else{
     /* This branch happens only when content is on overflow pages */
     if( ((pOp->p5 & (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG))!=0
@@ -2567,38 +2587,20 @@ case OP_Column: {
       **    2. the length(X) function if X is a blob, and
       **    3. if the content length is zero.
       ** So we might as well use bogus content rather than reading
-      ** content from disk.  NULL will work for the value for strings
-      ** and blobs and whatever is in the payloadSize64 variable
-      ** will work for everything else. */
-      sqlite3VdbeSerialGet(t<=13 ? (u8*)&payloadSize64 : 0, t, pDest);
+      ** content from disk. */
+      static u8 aZero[8];  /* This is the bogus content */
+      sqlite3VdbeSerialGet(aZero, t, pDest);
     }else{
       rc = sqlite3VdbeMemFromBtree(pCrsr, aOffset[p2], len, !pC->isTable,
                                    pDest);
-      if( rc!=SQLITE_OK ){
-        goto op_column_error;
+      if( rc==SQLITE_OK ){
+        sqlite3VdbeSerialGet((const u8*)pDest->z, t, pDest);
+        pDest->flags &= ~MEM_Ephem;
       }
-      sqlite3VdbeSerialGet((const u8*)pDest->z, t, pDest);
-      pDest->flags &= ~MEM_Ephem;
     }
   }
-  pDest->enc = encoding;
 
 op_column_out:
-  /* If the column value is an ephemeral string, go ahead and persist
-  ** that string in case the cursor moves before the column value is
-  ** used.  The following code does the equivalent of Deephemeralize()
-  ** but does it faster. */
-  if( (pDest->flags & MEM_Ephem)!=0 && pDest->z ){
-    fx = pDest->flags & (MEM_Str|MEM_Blob);
-    assert( fx!=0 );
-    zData = (const u8*)pDest->z;
-    len = pDest->n;
-    if( sqlite3VdbeMemClearAndResize(pDest, len+2) ) goto no_mem;
-    memcpy(pDest->z, zData, len);
-    pDest->z[len] = 0;
-    pDest->z[len+1] = 0;
-    pDest->flags = fx|MEM_Term;
-  }
 op_column_error:
   UPDATE_MAX_BLOBSIZE(pDest);
   REGISTER_TRACE(pOp->p3, pDest);
-- 
2.47.2