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Overview
Comment:Updates to the sqlite3_stmt_scanstatus() documentation. No changes to code.
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SHA1:d97c324eb1d870c994911c53fbf84205f4e3e7a1
User & Date: drh 2014-11-03 18:03:00
Context
2014-11-04
12:11
Add the SQLITE_CONFIG_PCACHE_HDRSZ option for sqlite3_config(). check-in: 6eb03e62 user: drh tags: trunk
2014-11-03
18:03
Updates to the sqlite3_stmt_scanstatus() documentation. No changes to code. check-in: d97c324e user: drh tags: trunk
16:56
Add the experimental sqlite3_stmt_scanstatus() API. For comparing the number of rows actually visited by a loop with the estimate used by the query planner. check-in: ab3b0fc5 user: dan tags: trunk
Changes
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Changes to src/sqlite.h.in.

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*/
#define SQLITE_ROLLBACK 1
/* #define SQLITE_IGNORE 2 // Also used by sqlite3_authorizer() callback */
#define SQLITE_FAIL     3
/* #define SQLITE_ABORT 4  // Also an error code */
#define SQLITE_REPLACE  5


/* CAPI3REF: Prepared Statement Scan Status Opcodes
** KEYWORDS: {scanstatus option}
**
** The following constants can be used for the T parameter to the
** [sqlite3_stmt_scanstatus(S,X,T,V)] interface.  Each constant designates a
** different metric for sqlite3_stmt_scanstatus() to return.
**
** <dl>
** [[SQLITE_SCANSTAT_NLOOP]] <td>SQLITE_SCANSTAT_NLOOP</dt>
** <dd>The [sqlite3_int64] variable pointed to by the T parameter will be set to the
** total number of times that the X-th loop has run.</dd>
**
** [[SQLITE_SCANSTAT_NVISIT]] <td>SQLITE_SCANSTAT_NVISIT</dt>
** <dd>The [sqlite3_int64] variable pointed to by the T parameter will be set to the
** total number of rows visited by the X-th loop.</dd>
**
** [[SQLITE_SCANSTAT_EST]] <td>SQLITE_SCANSTAT_EST</dt>
** <dd>The [sqlite3_int64] variable pointed to by the T parameter will be set to the
** query planner's estimate for the number of rows visited for each
** iteration of the X-th loop.  If the query planner's estimate was accurate,
** then this value should be approximately NVISIT/NLOOP.
**
** [[SQLITE_SCANSTAT_NAME]] <td>SQLITE_SCANSTAT_NAME</dt>
** <dd>The "const char *" variable pointed to by the T parameter will be set to 
** a zero-terminated UTF-8 string containing the name of the index or table used
** for the X-th loop.
**
** [[SQLITE_SCANSTAT_EXPLAIN]] <td>SQLITE_SCANSTAT_EXPLAIN</dt>
** <dd>The "const char *" variable pointed to by the T parameter will be set to 
** a zero-terminated UTF-8 string containing the [EXPLAIN QUERY PLAN] description
** for the X-th loop.
** </dl>
*/
#define SQLITE_SCANSTAT_NLOOP    0
#define SQLITE_SCANSTAT_NVISIT   1
#define SQLITE_SCANSTAT_EST      2
................................................................................
** CAPI3REF: Prepared Statement Scan Status
**
** Return status data for a single loop within query pStmt.
**
** 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.
**
** 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.
**
** This API is only available if the library is built with pre-processor
** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.


*/
SQLITE_EXPERIMENTAL int sqlite3_stmt_scanstatus(
  sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
  int idx,                  /* Index of loop to report on */
  int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
  void *pOut                /* Result written here */
);     

/*
** CAPI3REF: Zero Scan-Status Counters
**
** Zero all sqlite3_stmt_scanstatus() related event counters.
**
** This API is only available if the library is built with pre-processor
** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.
*/
SQLITE_EXPERIMENTAL void sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);









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*/
#define SQLITE_ROLLBACK 1
/* #define SQLITE_IGNORE 2 // Also used by sqlite3_authorizer() callback */
#define SQLITE_FAIL     3
/* #define SQLITE_ABORT 4  // Also an error code */
#define SQLITE_REPLACE  5

/*
** CAPI3REF: Prepared Statement Scan Status Opcodes
** KEYWORDS: {scanstatus options}
**
** The following constants can be used for the T parameter to the
** [sqlite3_stmt_scanstatus(S,X,T,V)] interface.  Each constant designates a
** different metric for sqlite3_stmt_scanstatus() to return.
**
** <dl>
** [[SQLITE_SCANSTAT_NLOOP]] <dt>SQLITE_SCANSTAT_NLOOP</dt>
** <dd>^The [sqlite3_int64] variable pointed to by the T parameter will be set to the
** total number of times that the X-th loop has run.</dd>
**
** [[SQLITE_SCANSTAT_NVISIT]] <dt>SQLITE_SCANSTAT_NVISIT</dt>
** <dd>^The [sqlite3_int64] variable pointed to by the T parameter will be set to the
** total number of rows visited by the X-th loop.</dd>
**
** [[SQLITE_SCANSTAT_EST]] <dt>SQLITE_SCANSTAT_EST</dt>
** <dd>^The [sqlite3_int64] variable pointed to by the T parameter will be set to the
** query planner's estimate for the number of rows visited for each
** iteration of the X-th loop.  If the query planner's estimate was accurate,
** then this value should be approximately NVISIT/NLOOP.
**
** [[SQLITE_SCANSTAT_NAME]] <dt>SQLITE_SCANSTAT_NAME</dt>
** <dd>^The "const char *" variable pointed to by the T parameter will be set to 
** a zero-terminated UTF-8 string containing the name of the index or table used
** for the X-th loop.
**
** [[SQLITE_SCANSTAT_EXPLAIN]] <dt>SQLITE_SCANSTAT_EXPLAIN</dt>
** <dd>^The "const char *" variable pointed to by the T parameter will be set to 
** a zero-terminated UTF-8 string containing the [EXPLAIN QUERY PLAN] description
** for the X-th loop.
** </dl>
*/
#define SQLITE_SCANSTAT_NLOOP    0
#define SQLITE_SCANSTAT_NVISIT   1
#define SQLITE_SCANSTAT_EST      2
................................................................................
** CAPI3REF: Prepared Statement Scan Status
**
** Return status data for a single loop within query pStmt.
**
** 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.
**
** ^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.
**
** This API is only available if the library is built with pre-processor
** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.
**
** See also: [sqlite3_stmt_scanstatus_reset()]
*/
SQLITE_EXPERIMENTAL int sqlite3_stmt_scanstatus(
  sqlite3_stmt *pStmt,      /* Prepared statement for which info desired */
  int idx,                  /* Index of loop to report on */
  int iScanStatusOp,        /* Information desired.  SQLITE_SCANSTAT_* */
  void *pOut                /* Result written here */
);     

/*
** CAPI3REF: Zero Scan-Status Counters
**
** ^Zero all [sqlite3_stmt_scanstatus()] related event counters.
**
** This API is only available if the library is built with pre-processor
** symbol [SQLITE_ENABLE_STMT_SCANSTATUS] defined.
*/
SQLITE_EXPERIMENTAL void sqlite3_stmt_scanstatus_reset(sqlite3_stmt*);