Enhance the EXPLAIN QUERY PLAN output to use symbolic names to describe

subqueries, where possible, instead of cryptic subquery index numbers.
And in other ways, make the EQP output cleaner and easier to read.  Little
code is changed, but many of the test results had to be tweaked to align
with the new output format.

FossilOrigin-Name: f8e28308fdb45fbdef30003320d653410d69bb8ec92eef35c4245a99e2d0603b

1 files changed, 22 insertions, 13 deletions

diff --git a/src/printf.c b/src/printf.c
index 9aab863ed..6f3b5681a 100644
--- a/src/printf.c
+++ b/src/printf.c
@@ -29,7 +29,7 @@
 #define etSQLESCAPE2 10 /* Strings with '\'' doubled and enclosed in '',
                           NULL pointers replaced by SQL NULL.  %Q */
 #define etTOKEN      11 /* a pointer to a Token structure */
-#define etSRCLIST    12 /* a pointer to a SrcList */
+#define etSRCITEM    12 /* a pointer to a SrcItem */
 #define etPOINTER    13 /* The %p conversion */
 #define etSQLESCAPE3 14 /* %w -> Strings with '\"' doubled */
 #define etORDINAL    15 /* %r -> 1st, 2nd, 3rd, 4th, etc.  English only */
@@ -95,10 +95,16 @@ static const et_info fmtinfo[] = {
 
   /* All the rest are undocumented and are for internal use only */
   {  'T',  0, 0, etTOKEN,      0,  0 },
-  {  'S',  0, 0, etSRCLIST,    0,  0 },
+  {  'S',  0, 0, etSRCITEM,    0,  0 },
   {  'r', 10, 1, etORDINAL,    0,  0 },
 };
 
+/* Notes:
+**
+**    %S    Takes a pointer to SrcItem.  Shows name or database.name
+**    %!S   Like %S but prefer the zName over the zAlias
+*/
+
 /* Floating point constants used for rounding */
 static const double arRound[] = {
   5.0e-01, 5.0e-02, 5.0e-03, 5.0e-04, 5.0e-05,
@@ -853,21 +859,24 @@ void sqlite3_str_vappendf(
         length = width = 0;
         break;
       }
-      case etSRCLIST: {
-        SrcList *pSrc;
-        int k;
+      case etSRCITEM: {
         SrcItem *pItem;
         if( (pAccum->printfFlags & SQLITE_PRINTF_INTERNAL)==0 ) return;
-        pSrc = va_arg(ap, SrcList*);
-        k = va_arg(ap, int);
-        pItem = &pSrc->a[k];
+        pItem = va_arg(ap, SrcItem*);
         assert( bArgList==0 );
-        assert( k>=0 && k<pSrc->nSrc );
-        if( pItem->zDatabase ){
-          sqlite3_str_appendall(pAccum, pItem->zDatabase);
-          sqlite3_str_append(pAccum, ".", 1);
+        if( pItem->zAlias && !flag_altform2 ){
+          sqlite3_str_appendall(pAccum, pItem->zAlias);
+        }else if( pItem->zName ){
+          if( pItem->zDatabase ){
+            sqlite3_str_appendall(pAccum, pItem->zDatabase);
+            sqlite3_str_append(pAccum, ".", 1);
+          }
+          sqlite3_str_appendall(pAccum, pItem->zName);
+        }else if( pItem->zAlias ){
+          sqlite3_str_appendall(pAccum, pItem->zAlias);
+        }else if( pItem->pSelect ){
+          sqlite3_str_appendf(pAccum, "SUBQUERY %u", pItem->pSelect->selId);
         }
-        sqlite3_str_appendall(pAccum, pItem->zName);
         length = width = 0;
         break;
       }