Add a procedure to handle the messy details of allocating an Index object

from the heap.

FossilOrigin-Name: 45efc94f9a8169433ffcb4aa35760551c55df4c4

3 files changed, 41 insertions, 29 deletions

diff --git a/src/build.c b/src/build.c
index cac5c89d4..acd498350 100644
--- a/src/build.c
+++ b/src/build.c
@@ -2516,6 +2516,40 @@ static void sqlite3RefillIndex(Parse *pParse, Index *pIndex, int memRootPage){
 }
 
 /*
+** Allocate heap space to hold an Index object with nCol columns.
+**
+** Increase the allocation size to provide an extra nExtra bytes
+** of 8-byte aligned space after the Index object and return a
+** pointer to this extra space in *ppExtra.
+*/
+Index *sqlite3AllocateIndexObject(
+  sqlite3 *db,         /* Database connection */
+  int nCol,            /* Number of columns in the index */
+  int nExtra,          /* Number of bytes of extra space to alloc */
+  char **ppExtra       /* Pointer to the "extra" space */
+){
+  Index *p;            /* Allocated index object */
+  int nByte;           /* Bytes of space for Index object + arrays */
+
+  nByte = ROUND8(sizeof(Index)) +              /* Index structure  */
+          ROUND8(sizeof(char*)*nCol) +         /* Index.azColl     */
+          ROUND8(sizeof(tRowcnt)*(nCol+1) +    /* Index.aiRowEst   */
+                 sizeof(int)*nCol +            /* Index.aiColumn   */
+                 sizeof(u8)*nCol);             /* Index.aSortOrder */
+  p = sqlite3DbMallocZero(db, nByte + nExtra);
+  if( p ){
+    char *pExtra = ((char*)p)+ROUND8(sizeof(Index));
+    p->azColl = (char**)pExtra;      pExtra += ROUND8(sizeof(char*)*nCol);
+    p->aiRowEst = (tRowcnt*)pExtra;  pExtra += sizeof(tRowcnt)*(nCol+1);
+    p->aiColumn = (int*)pExtra;      pExtra += sizeof(int)*nCol;
+    p->aSortOrder = (u8*)pExtra;
+    p->nColumn = nCol;
+    *ppExtra = ((char*)p) + nByte;
+  }
+  return p;
+}
+
+/*
 ** Create a new index for an SQL table.  pName1.pName2 is the name of the index 
 ** and pTblList is the name of the table that is to be indexed.  Both will 
 ** be NULL for a primary key or an index that is created to satisfy a
@@ -2558,7 +2592,6 @@ Index *sqlite3CreateIndex(
   Token *pName = 0;    /* Unqualified name of the index to create */
   struct ExprList_item *pListItem; /* For looping over pList */
   const Column *pTabCol;           /* A column in the table */
-  int nCol;                        /* Number of columns */
   int nExtra = 0;                  /* Space allocated for zExtra[] */
   char *zExtra;                    /* Extra space after the Index object */
 
@@ -2730,29 +2763,15 @@ Index *sqlite3CreateIndex(
   ** Allocate the index structure. 
   */
   nName = sqlite3Strlen30(zName);
-  nCol = pList->nExpr;
-  pIndex = sqlite3DbMallocZero(db, 
-      ROUND8(sizeof(Index)) +              /* Index structure  */
-      ROUND8(sizeof(tRowcnt)*(nCol+1)) +   /* Index.aiRowEst   */
-      sizeof(char *)*nCol +                /* Index.azColl     */
-      sizeof(int)*nCol +                   /* Index.aiColumn   */
-      sizeof(u8)*nCol +                    /* Index.aSortOrder */
-      nName + 1 +                          /* Index.zName      */
-      nExtra                               /* Collation sequence names */
-  );
+  pIndex = sqlite3AllocateIndexObject(db, pList->nExpr,
+                                      nName + nExtra + 1, &zExtra);
   if( db->mallocFailed ){
     goto exit_create_index;
   }
-  zExtra = (char*)pIndex;
-  pIndex->aiRowEst = (tRowcnt*)&zExtra[ROUND8(sizeof(Index))];
-  pIndex->azColl = (char**)
-     ((char*)pIndex->aiRowEst + ROUND8(sizeof(tRowcnt)*nCol+1));
   assert( EIGHT_BYTE_ALIGNMENT(pIndex->aiRowEst) );
   assert( EIGHT_BYTE_ALIGNMENT(pIndex->azColl) );
-  pIndex->aiColumn = (int *)(&pIndex->azColl[nCol]);
-  pIndex->aSortOrder = (u8 *)(&pIndex->aiColumn[nCol]);
-  pIndex->zName = (char *)(&pIndex->aSortOrder[nCol]);
-  zExtra = (char *)(&pIndex->zName[nName+1]);
+  pIndex->zName = zExtra;
+  zExtra += nName + 1;
   memcpy(pIndex->zName, zName, nName+1);
   pIndex->pTable = pTab;
   pIndex->nColumn = pList->nExpr;
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index e69f274bc..11053b9af 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2826,6 +2826,7 @@ void sqlite3SrcListShiftJoinType(SrcList*);
 void sqlite3SrcListAssignCursors(Parse*, SrcList*);
 void sqlite3IdListDelete(sqlite3*, IdList*);
 void sqlite3SrcListDelete(sqlite3*, SrcList*);
+Index *sqlite3AllocateIndexObject(sqlite3*,int,int,char**);
 Index *sqlite3CreateIndex(Parse*,Token*,Token*,SrcList*,ExprList*,int,Token*,
                           Expr*, int, int);
 void sqlite3DropIndex(Parse*, SrcList*, int);
diff --git a/src/where.c b/src/where.c
index d89ce6513..d9f4a9c42 100644
--- a/src/where.c
+++ b/src/where.c
@@ -2008,7 +2008,6 @@ static void constructAutomaticIndex(
   int nColumn;                /* Number of columns in the constructed index */
   WhereTerm *pTerm;           /* A single term of the WHERE clause */
   WhereTerm *pWCEnd;          /* End of pWC->a[] */
-  int nByte;                  /* Byte of memory needed for pIdx */
   Index *pIdx;                /* Object describing the transient index */
   Vdbe *v;                    /* Prepared statement under construction */
   int addrInit;               /* Address of the initialization bypass jump */
@@ -2021,6 +2020,7 @@ static void constructAutomaticIndex(
   int mxBitCol;               /* Maximum column in pSrc->colUsed */
   CollSeq *pColl;             /* Collating sequence to on a column */
   WhereLoop *pLoop;           /* The Loop object */
+  char *zNotUsed;             /* Extra space on the end of pIdx */
   Bitmask idxCols;            /* Bitmap of columns used for indexing */
   Bitmask extraCols;          /* Bitmap of additional columns */
   u8 sentWarning = 0;         /* True if a warnning has been issued */
@@ -2083,18 +2083,10 @@ static void constructAutomaticIndex(
   pLoop->wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY;
 
   /* Construct the Index object to describe this index */
-  nByte = sizeof(Index);
-  nByte += nColumn*sizeof(int);     /* Index.aiColumn */
-  nByte += nColumn*sizeof(char*);   /* Index.azColl */
-  nByte += nColumn;                 /* Index.aSortOrder */
-  pIdx = sqlite3DbMallocZero(pParse->db, nByte);
+  pIdx = sqlite3AllocateIndexObject(pParse->db, nColumn, 0, &zNotUsed);
   if( pIdx==0 ) return;
   pLoop->u.btree.pIndex = pIdx;
-  pIdx->azColl = (char**)&pIdx[1];
-  pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
-  pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
   pIdx->zName = "auto-index";
-  pIdx->nColumn = nColumn;
   pIdx->pTable = pTable;
   n = 0;
   idxCols = 0;