From: drh <drh@noemail.net>
Date: Sat, 12 Jun 2004 18:12:15 +0000 (+0000)
Subject: Improve the speed of OP_Column through better caching. (CVS 1577)
X-Git-Tag: version-3.0.0~40
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e61cffc20326c4fd4369b8bed68134b42b0591ed;p=thirdparty%2Fsqlite.git

Improve the speed of OP_Column through better caching. (CVS 1577)

FossilOrigin-Name: f687977a28eda5ce0aa1cba2fdfb0152443032bc
---

diff --git a/manifest b/manifest
index 3f7e2ae8a6..42030e5a20 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\stypo\sin\sthe\slocking\sdocument.\s(CVS\s1576)
-D 2004-06-12T14:11:38
+C Improve\sthe\sspeed\sof\sOP_Column\sthrough\sbetter\scaching.\s(CVS\s1577)
+D 2004-06-12T18:12:16
 F Makefile.in ab7b0d5118e2da97bac66be8684a1034e3500f5a
 F Makefile.linux-gcc a9e5a0d309fa7c38e7c14d3ecf7690879d3a5457
 F README f1de682fbbd94899d50aca13d387d1b3fd3be2dd
@@ -41,7 +41,7 @@ F src/legacy.c ad23746f15f67e34577621b1875f639c94839e1f
 F src/main.c 9061fff2b04759d849155a334bf2a9f158d325d7
 F src/md5.c d77a389955759c8329bb357e3d71bac3d6eb710b
 F src/os.h 23c69c5084e71b5fe199ff1c4e35a4aded0f1380
-F src/os_common.h 6393ac67a3a7b4aea19ff17529980ecf77eb2348
+F src/os_common.h ba1b7306e16e2091718f2c48db0fe6c1d7a31bb8
 F src/os_mac.c b823874690615ace0dd520d3ad1fe8bfd864b7e0
 F src/os_mac.h 51d2445f47e182ed32d3bd6937f81070c6fd9bd4
 F src/os_unix.c 7ece785e36c4ecb57c73db8d374b56912d742c4a
@@ -71,9 +71,9 @@ F src/update.c 168b6d523087ca4545b74ec9f3102b1f3c6b1e38
 F src/utf.c e16737b3fc4201bf7ce9bd8ced5250596aa31b76
 F src/util.c 90375fa253137562d536ccdd40b297f0fd7413fc
 F src/vacuum.c b921eb778842592e1fb48a9d4cef7e861103878f
-F src/vdbe.c 026b78bc404a2585aaefbf876295ed3ae892d769
+F src/vdbe.c 9f941bbdf0bcbc18fbdfceecbc2322e82084e094
 F src/vdbe.h 46f74444a213129bc4b5ce40124dd8ed613b0cde
-F src/vdbeInt.h c4ff480cd8f859c9862d759aebd0fe5ebaef47a1
+F src/vdbeInt.h 1cc767a63eefd1d1114e190336588c6d4f70a6a0
 F src/vdbeapi.c ee350b552fc4c1c695b760f914f69e9c5556e829
 F src/vdbeaux.c 1d0dbaf73c89bd1cc27abad19ee0aa26ab5d03f4
 F src/vdbemem.c 34f59988831ea032b7f526c2c73175f9f4c0f3ad
@@ -223,7 +223,7 @@ F www/support.tcl 1801397edd271cc39a2aadd54e701184b5181248
 F www/tclsqlite.tcl 19191cf2a1010eaeff74c51d83fd5f5a4d899075
 F www/vdbe.tcl 59288db1ac5c0616296b26dce071c36cb611dfe9
 F www/whentouse.tcl a8335bce47cc2fddb07f19052cb0cb4d9129a8e4
-P 5903f53828b5d282b33e27813417e4317c9ecf0b
-R a46c51da808bad8e24d7946d300b2226
+P 99a7bd83ac38e14bb936a834634313cf98279a62
+R 1e1692dcb3026c03937468eb4d723051
 U drh
-Z e597c81eeb6dd60916f877dd834b0e9c
+Z 511db11f04adc59072cae9559d18a6b6
diff --git a/manifest.uuid b/manifest.uuid
index 8b0b602465..3a7b8c7357 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-99a7bd83ac38e14bb936a834634313cf98279a62
\ No newline at end of file
+f687977a28eda5ce0aa1cba2fdfb0152443032bc
\ No newline at end of file
diff --git a/src/os_common.h b/src/os_common.h
index 088750963b..a8ac2707ae 100644
--- a/src/os_common.h
+++ b/src/os_common.h
@@ -24,7 +24,7 @@
 ** on i486 hardware.
 */
 int sqlite3_os_trace = 0;
-#if 1
+#ifdef SQLITE_DEBUG
 static int last_page = 0;
 __inline__ unsigned long long int hwtime(void){
   unsigned long long int x;
diff --git a/src/vdbe.c b/src/vdbe.c
index fc2d9cff87..4c1faef212 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -43,7 +43,7 @@
 ** in this file for details.  If in doubt, do not deviate from existing
 ** commenting and indentation practices when changing or adding code.
 **
-** $Id: vdbe.c,v 1.368 2004/06/12 09:25:25 danielk1977 Exp $
+** $Id: vdbe.c,v 1.369 2004/06/12 18:12:16 drh Exp $
 */
 #include "sqliteInt.h"
 #include "os.h"
@@ -1899,7 +1899,7 @@ case OP_Column: {
   int p1 = pOp->p1;  /* P1 value of the opcode */
   int p2 = pOp->p2;  /* column number to retrieve */
   Cursor *pC = 0;    /* The VDBE cursor */
-  char *zRec;        /* Pointer to record-data from stack or pseudo-table. */
+  char *zRec;        /* Pointer to complete record-data */
   BtCursor *pCrsr;   /* The BTree cursor */
   u32 *aType;        /* aType[i] holds the numeric type of the i-th column */
   u32 *aOffset;      /* aOffset[i] is offset to start of data for i-th column */
@@ -1916,9 +1916,15 @@ case OP_Column: {
   assert( p1<p->nCursor );
   pTos++;
 
-  /* This block sets the variable payloadSize, and if the data is coming
-  ** from the stack or from a pseudo-table zRec. If the data is coming
-  ** from a real cursor, then zRec is left as NULL.
+  /* This block sets the variable payloadSize to be the total number of
+  ** bytes in the record.
+  **
+  ** zRec is set to be the complete text of the record if it is available.
+  ** The complete record text is always available for pseudo-tables and
+  ** when we are decoded a record from the stack.  If the record is stored
+  ** in a cursor, the complete record text might be available in the 
+  ** pC->aRow cache.  Or it might not be.  If the data is unavailable,
+  ** zRec is set to NULL.
   **
   ** We also compute the number of columns in the record.  For cursors,
   ** the number of columns is stored in the Cursor.nField element.  For
@@ -1926,6 +1932,7 @@ case OP_Column: {
   ** which is the number of records.
   */
   if( p1<0 ){
+    /* Take the record off of the stack */
     Mem *pRec = &pTos[p1];
     Mem *pCnt = &pRec[-1];
     assert( pRec>=p->aStack );
@@ -1936,6 +1943,7 @@ case OP_Column: {
     assert( pCnt->flags & MEM_Int );
     nField = pCnt->i;
   }else if( (pC = p->apCsr[p1])->pCursor!=0 ){
+    /* The record is stored in a B-Tree */
     sqlite3VdbeCursorMoveto(pC);
     zRec = 0;
     pCrsr = pC->pCursor;
@@ -1943,6 +1951,7 @@ case OP_Column: {
       payloadSize = 0;
     }else if( pC->cacheValid ){
       payloadSize = pC->payloadSize;
+      zRec = pC->aRow;
     }else if( pC->keyAsData ){
       i64 payloadSize64;
       sqlite3BtreeKeySize(pCrsr, &payloadSize64);
@@ -1952,6 +1961,7 @@ case OP_Column: {
     }
     nField = pC->nField;
   }else if( pC->pseudoTable ){
+    /* The record is the sole entry of a pseudo-table */
     payloadSize = pC->nData;
     zRec = pC->pData;
     pC->cacheValid = 0;
@@ -1996,11 +2006,27 @@ case OP_Column: {
       }else{
         zData = (char*)sqlite3BtreeDataFetch(pCrsr, &avail);
       }
+      /* If KeyFetch()/DataFetch() managed to get the entire payload,
+      ** save the payload in the pC->aRow cache.  That will save us from
+      ** having to make additional calls to fetch the content portion of
+      ** the record.
+      */
+      if( avail>=payloadSize ){
+        zRec = pC->aRow = zData;
+      }else{
+        pC->aRow = 0;
+      }
     }
     idx = sqlite3GetVarint32(zData, &szHdr);
 
-    /* Get the complete header text */
-    if( !zRec && avail<idx ){
+
+    /* The KeyFetch() or DataFetch() above are fast and will get the entire
+    ** record header in most cases.  But they will fail to get the complete
+    ** record header if the record header does not fit on a single page
+    ** in the B-Tree.  When that happens, use sqlite3VdbeMemFromBtree() to
+    ** acquire the complete header text.
+    */
+    if( !zRec && avail<szHdr ){
       rc = sqlite3VdbeMemFromBtree(pCrsr, 0, szHdr, pC->keyAsData, &sMem);
       if( rc!=SQLITE_OK ){
         goto abort_due_to_error;
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
index 709287d92e..39f27c1f60 100644
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -83,11 +83,14 @@ struct Cursor {
   int nField;           /* Number of fields in the header */
 
   /* Cached information about the header for the data record that the
-  ** cursor is currently pointing to */
+  ** cursor is currently pointing to.  Only valid if cacheValid is true.
+  ** zRow might point to (ephemeral) data for the current row, or it might
+  ** be NULL. */
   Bool cacheValid;      /* True if the cache is valid */
   int payloadSize;      /* Total number of bytes in the record */
   u32 *aType;           /* Type values for all entries in the record */
   u32 *aOffset;         /* Cached offsets to the start of each columns data */
+  u8 *aRow;             /* Data for the current row, if all on one page */
 };
 typedef struct Cursor Cursor;