Add the "colUsed" field to the sqlite3_index_info structure passed to virtual table xBestIndex methods. To indicate the subset of the virtual table columns that may be required by the current scan.

FossilOrigin-Name: 116b206494eb8ba963c7c5acfbf9e7b6db11c79c

1 files changed, 34 insertions, 4 deletions

diff --git a/src/test8.c b/src/test8.c
index 0c5dc0206..3e506e36b 100644
--- a/src/test8.c
+++ b/src/test8.c
@@ -746,6 +746,34 @@ static void string_concat(char **pzStr, char *zAppend, int doFree, int *pRc){
 }
 
 /*
+** This function returns a pointer to an sqlite3_malloc()ed buffer 
+** containing the select-list (the thing between keywords SELECT and FROM)
+** to query the underlying real table with for the scan described by
+** argument pIdxInfo.
+**
+** If the current SQLite version is earlier than 3.10.0, this is just "*"
+** (select all columns). Or, for version 3.10.0 and greater, the list of
+** columns identified by the pIdxInfo->colUsed mask.
+*/
+static char *echoSelectList(echo_vtab *pTab, sqlite3_index_info *pIdxInfo){
+  char *zRet = 0;
+  if( sqlite3_libversion_number()<3010000 ){
+    zRet = sqlite3_mprintf(", *");
+  }else{
+    int i;
+    for(i=0; i<pTab->nCol; i++){
+      if( pIdxInfo->colUsed & ((sqlite3_uint64)1 << (i>=63 ? 63 : i)) ){
+        zRet = sqlite3_mprintf("%z, %s", zRet, pTab->aCol[i]);
+      }else{
+        zRet = sqlite3_mprintf("%z, NULL", zRet);
+      }
+      if( !zRet ) break;
+    }
+  }
+  return zRet;
+}
+
+/*
 ** The echo module implements the subset of query constraints and sort
 ** orders that may take advantage of SQLite indices on the underlying
 ** real table. For example, if the real table is declared as:
@@ -770,6 +798,7 @@ static void string_concat(char **pzStr, char *zAppend, int doFree, int *pRc){
 static int echoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
   int ii;
   char *zQuery = 0;
+  char *zCol = 0;
   char *zNew;
   int nArg = 0;
   const char *zSep = "WHERE";
@@ -817,10 +846,11 @@ static int echoBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
     }
   }
 
-  zQuery = sqlite3_mprintf("SELECT rowid, * FROM %Q", pVtab->zTableName);
-  if( !zQuery ){
-    return SQLITE_NOMEM;
-  }
+  zCol = echoSelectList(pVtab, pIdxInfo);
+  if( !zCol ) return SQLITE_NOMEM;
+  zQuery = sqlite3_mprintf("SELECT rowid%z FROM %Q", zCol, pVtab->zTableName);
+  if( !zQuery ) return SQLITE_NOMEM;
+
   for(ii=0; ii<pIdxInfo->nConstraint; ii++){
     const struct sqlite3_index_constraint *pConstraint;
     struct sqlite3_index_constraint_usage *pUsage;