Update comments in sqlite.h.in to account for sqlite3_stmt_scanstatus_v2().

FossilOrigin-Name: 009462f2344b1f468cf9440343a47fec68d783a2bfb4fa6168bb227ec910b918

src/sqlite.h.in

@@ -9886,6 +9886,10 @@ int sqlite3_vtab_rhs_value(sqlite3_index_info*, int, sqlite3_value **ppVal);
 ** managed by the prepared statement S and will be automatically freed when
 ** S is finalized.
 **
+** Not all values are available for all query elements. When a value is
+** not available, the output variable is set to -1 if the value is numeric,
+** or to NULL if it is a string (SQLITE_SCANSTAT_NAME).
+**
 ** <dl>
 ** [[SQLITE_SCANSTAT_NLOOP]] <dt>SQLITE_SCANSTAT_NLOOP</dt>
 ** <dd>^The [sqlite3_int64] variable pointed to by the V parameter will be
@@ -9913,13 +9917,25 @@ int sqlite3_vtab_rhs_value(sqlite3_index_info*, int, sqlite3_value **ppVal);
 ** to a zero-terminated UTF-8 string containing the [EXPLAIN QUERY PLAN]
 ** description for the X-th loop.
 **
-** [[SQLITE_SCANSTAT_SELECTID]] <dt>SQLITE_SCANSTAT_SELECT</dt>
+** [[SQLITE_SCANSTAT_SELECTID]] <dt>SQLITE_SCANSTAT_SELECTID</dt>
 ** <dd>^The "int" variable pointed to by the V parameter will be set to the
-** "select-id" for the X-th loop.  The select-id identifies which query or
-** subquery the loop is part of.  The main query has a select-id of zero.
-** The select-id is the same value as is output in the first column
-** of an [EXPLAIN QUERY PLAN] query.
+** id for the X-th query plan element. The id value is unique within the
+** statement. The select-id is the same value as is output in the first 
+** column of an [EXPLAIN QUERY PLAN] query.
 ** </dl>
+**
+** [[SQLITE_SCANSTAT_PARENTID]] <dt>SQLITE_SCANSTAT_PARENTID</dt>
+** <dd>The "int" variable pointed to by the V parameter will be set to the
+** the id of the parent of the current query element, if applicable, or
+** to zero if the query element has no parent. This is the same value as
+** returned in the second column of an [EXPLAIN QUERY PLAN] query. 
+**
+** [[SQLITE_SCANSTAT_NCYCLE]] <dt>SQLITE_SCANSTAT_NCYCLE</dt>
+** <dd>The sqlite3_int64 output value is set to the number of cycles,
+** according to the processor time-stamp counter, that elapsed while the
+** query element was being processed. This value is not available for
+** all query elements - if it is unavailable the output variable is
+** set to -1.
 */
 #define SQLITE_SCANSTAT_NLOOP    0
 #define SQLITE_SCANSTAT_NVISIT   1
@@ -9934,7 +9950,7 @@ int sqlite3_vtab_rhs_value(sqlite3_index_info*, int, sqlite3_value **ppVal);
 ** CAPI3REF: Prepared Statement Scan Status
 ** METHOD: sqlite3_stmt
 **
-** This interface returns information about the predicted and measured
+** These interfaces return information about the predicted and measured
 ** performance for pStmt.  Advanced applications can use this
 ** interface to compare the predicted and the measured performance and
 ** issue warnings and/or rerun [ANALYZE] if discrepancies are found.
@@ -9945,19 +9961,25 @@ int sqlite3_vtab_rhs_value(sqlite3_index_info*, int, sqlite3_value **ppVal);
 **
 ** The "iScanStatusOp" parameter determines which status information to return.
 ** The "iScanStatusOp" must be one of the [scanstatus options] or the behavior
-** of this interface is undefined.
-** ^The requested measurement is written into a variable pointed to by
-** the "pOut" parameter.
-** Parameter "idx" identifies the specific loop to retrieve statistics for.
-** Loops are numbered starting from zero. ^If idx is out of range - less than
-** zero or greater than or equal to the total number of loops used to implement
-** the statement - a non-zero value is returned and the variable that pOut
-** points to is unchanged.
+** of this interface is undefined. ^The requested measurement is written into 
+** a variable pointed to by the "pOut" parameter.
 **
-** ^Statistics might not be available for all loops in all statements. ^In cases
-** where there exist loops with no available statistics, this function behaves
-** as if the loop did not exist - it returns non-zero and leave the variable
-** that pOut points to unchanged.
+** The "flags" parameter must be passed a mask of flags. At present only
+** one flag is defined - SQLITE_SCANSTAT_COMPLEX. If SQLITE_SCANSTAT_COMPLEX
+** is specified, then status information is available for all elements 
+** of a query plan that are reported by "EXPLAIN QUERY PLAN" output. If
+** SQLITE_SCANSTAT_COMPLEX is not specified, then only query plan elements
+** that correspond to query loops (the "SCAN..." and "SEARCH..." elements of
+** the EXPLAIN QUERY PLAN output) are available. Invoking API
+** sqlite3_stmt_scanstatus() is equivalent to calling 
+** sqlite3_stmt_scanstatus_v2() with a zeroed flags parameter.
+** 
+** Parameter "idx" identifies the specific query element to retrieve statistics
+** for. Query elements are numbered starting from zero. A value of -1 may be
+** to query for statistics regarding the entire query. ^If idx is out of range
+** - less than -1 or greater than or equal to the total number of query 
+** elements used to implement the statement - a non-zero value is returned and
+** the variable that pOut points to is unchanged.
 **
 ** See also: [sqlite3_stmt_scanstatus_reset()]
 */
@@ -9967,7 +9989,6 @@ int sqlite3_stmt_scanstatus(
   int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
   void *pOut                /* Result written here */
 );     
-
 int sqlite3_stmt_scanstatus_v2(
   sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
   int idx,                  /* Index of loop to report on */
@@ -9976,6 +9997,10 @@ int sqlite3_stmt_scanstatus_v2(
   void *pOut                /* Result written here */
 );     
 
+/*
+** CAPI3REF: Prepared Statement Scan Status
+** KEYWORDS: {scan status flags}
+*/
 #define SQLITE_SCANSTAT_COMPLEX 0x0001
 
 /*

src/vdbeapi.c

@@ -2258,7 +2258,6 @@ int sqlite3_stmt_scanstatus(
   return sqlite3_stmt_scanstatus_v2(pStmt, iScan, iScanStatusOp, 0, pOut);
 }
 
-
 /*
 ** Zero all counters associated with the sqlite3_stmt_scanstatus() data.
 */

src/vdbeaux.c

@@ -1128,6 +1128,13 @@ void sqlite3VdbeScanStatus(
   }
 }
 
+/*
+** Add the range of instructions from addrStart to addrEnd (inclusive) to
+** the set of those corresponding to the sqlite3_stmt_scanstatus() counters
+** associated with the OP_Explain instruction at addrExplain. The
+** sum of the sqlite3Hwtime() values for each of these instructions 
+** will be returned for SQLITE_SCANSTAT_NCYCLE requests.
+*/
 void sqlite3VdbeScanStatusRange(
   Vdbe *p, 
   int addrExplain, 
@@ -1153,6 +1160,11 @@ void sqlite3VdbeScanStatusRange(
   }
 }
 
+/*
+** Set the addresses for the SQLITE_SCANSTAT_NLOOP and SQLITE_SCANSTAT_NROW
+** counters for the query element associated with the OP_Explain at
+** addrExplain.
+*/
 void sqlite3VdbeScanStatusCounters(
   Vdbe *p, 
   int addrExplain,