Set the TF_StatsUsed flag on tables when the query planner outcome is

affected by the sqlite_stat1 data.  Also, change the column names of the
"PRAGMA stats" command so that they are not keywords.

FossilOrigin-Name: fb2b8ae8310e4ea4b42354bbf36c3084a9d5c6d7

src/sqliteInt.h

@@ -1883,10 +1883,13 @@ struct Table {
 #define TF_Ephemeral       0x0002    /* An ephemeral table */
 #define TF_HasPrimaryKey   0x0004    /* Table has a primary key */
 #define TF_Autoincrement   0x0008    /* Integer primary key is autoincrement */
-#define TF_HasStat1        0x0010    /* Has STAT1 data */
+#define TF_HasStat1        0x0010    /* nRowLogEst set from sqlite_stat1 */
 #define TF_WithoutRowid    0x0020    /* No rowid.  PRIMARY KEY is the key */
 #define TF_NoVisibleRowid  0x0040    /* No user-visible "rowid" column */
 #define TF_OOOHidden       0x0080    /* Out-of-Order hidden columns */
+#define TF_SizeChng        0x0100    /* nRowLogEst might be inaccurate */
+#define TF_StatsUsed       0x0200    /* Query planner decisions affected by
+                                     ** Index.aiRowLogEst[] values */
 
 /*
 ** Test to see whether or not a table is a virtual table.  This is
@@ -2129,7 +2132,7 @@ struct Index {
   unsigned isResized:1;    /* True if resizeIndexObject() has been called */
   unsigned isCovering:1;   /* True if this is a covering index */
   unsigned noSkipScan:1;   /* Do not try to use skip-scan if true */
-  unsigned hasStat1:1;     /* True if stat1 data has been loaded */
+  unsigned hasStat1:1;     /* aiRowLogEst values come from sqlite_stat1 */
 #ifdef SQLITE_ENABLE_STAT3_OR_STAT4
   int nSample;             /* Number of elements in aSample[] */
   int nSampleCol;          /* Size of IndexSample.anEq[] and so on */