** 2017 April 07
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
typedef struct sqlite3expert sqlite3expert;
** Create a new sqlite3expert object.
** If successful, a pointer to the new object is returned and (*pzErr) set
** to NULL. Or, if an error occurs, NULL is returned and (*pzErr) set to
** an English-language error message. In this case it is the responsibility
** of the caller to eventually free the error message buffer using
sqlite3expert *sqlite3_expert_new(sqlite3 *db, char **pzErr);
** Configure an sqlite3expert object.
** By default, sqlite3_expert_analyze() generates sqlite_stat1 data for
** each candidate index. This involves scanning and sorting the entire
** contents of each user database table once for each candidate index
** associated with the table. For large databases, this can be
** prohibitively slow. This option allows the sqlite3expert object to
** be configured so that sqlite_stat1 data is instead generated based on a
** subset of each table, or so that no sqlite_stat1 data is used at all.
** A single integer argument is passed to this option. If the value is less
** than or equal to zero, then no sqlite_stat1 data is generated or used by
** the analysis - indexes are recommended based on the database schema only.
** Or, if the value is 100 or greater, complete sqlite_stat1 data is
** generated for each candidate index (this is the default). Finally, if the
** value falls between 0 and 100, then it represents the percentage of user
** table rows that should be considered when generating sqlite_stat1 data.
** // Do not generate any sqlite_stat1 data
** sqlite3_expert_config(pExpert, EXPERT_CONFIG_SAMPLE, 0);
** // Generate sqlite_stat1 data based on 10% of the rows in each table.
** sqlite3_expert_config(pExpert, EXPERT_CONFIG_SAMPLE, 10);
int sqlite3_expert_config(sqlite3expert *p, int op, ...);
#define EXPERT_CONFIG_SAMPLE 1 /* int */
** Specify zero or more SQL statements to be included in the analysis.
** Buffer zSql must contain zero or more complete SQL statements. This
** function parses all statements contained in the buffer and adds them
** to the internal list of statements to analyze. If successful, SQLITE_OK
** is returned and (*pzErr) set to NULL. Or, if an error occurs - for example
** due to a error in the SQL - an SQLite error code is returned and (*pzErr)
** may be set to point to an English language error message. In this case
** the caller is responsible for eventually freeing the error message buffer
** using sqlite3_free().
** If an error does occur while processing one of the statements in the
** buffer passed as the second argument, none of the statements in the
** buffer are added to the analysis.
** This function must be called before sqlite3_expert_analyze(). If a call
** to this function is made on an sqlite3expert object that has already
** been passed to sqlite3_expert_analyze() SQLITE_MISUSE is returned
** immediately and no statements are added to the analysis.
sqlite3expert *p, /* From a successful sqlite3_expert_new() */
const char *zSql, /* SQL statement(s) to add */
char **pzErr /* OUT: Error message (if any) */
** This function is called after the sqlite3expert object has been configured
** with all SQL statements using sqlite3_expert_sql() to actually perform
** the analysis. Once this function has been called, it is not possible to
** add further SQL statements to the analysis.
** If successful, SQLITE_OK is returned and (*pzErr) is set to NULL. Or, if
** an error occurs, an SQLite error code is returned and (*pzErr) set to
** point to a buffer containing an English language error message. In this
** case it is the responsibility of the caller to eventually free the buffer
** using sqlite3_free().
** If an error does occur within this function, the sqlite3expert object
** is no longer useful for any purpose. At that point it is no longer
** possible to add further SQL statements to the object or to re-attempt
** the analysis. The sqlite3expert object must still be freed using a call
int sqlite3_expert_analyze(sqlite3expert *p, char **pzErr);
** Return the total number of statements loaded using sqlite3_expert_sql().
** The total number of SQL statements may be different from the total number
** to calls to sqlite3_expert_sql().
** Return a component of the report.
** This function is called after sqlite3_expert_analyze() to extract the
** results of the analysis. Each call to this function returns either a
** NULL pointer or a pointer to a buffer containing a nul-terminated string.
** The value passed as the third argument must be one of the EXPERT_REPORT_*
** #define constants defined below.
** For some EXPERT_REPORT_* parameters, the buffer returned contains
** information relating to a specific SQL statement. In these cases that
** SQL statement is identified by the value passed as the second argument.
** SQL statements are numbered from 0 in the order in which they are parsed.
** If an out-of-range value (less than zero or equal to or greater than the
** value returned by sqlite3_expert_count()) is passed as the second argument
** along with such an EXPERT_REPORT_* parameter, NULL is always returned.
** Return the text of SQL statement iStmt.
** Return a buffer containing the CREATE INDEX statements for all recommended
** indexes for statement iStmt. If there are no new recommeded indexes, NULL
** is returned.
** Return a buffer containing the EXPLAIN QUERY PLAN output for SQL query
** iStmt after the proposed indexes have been added to the database schema.
** Return a pointer to a buffer containing the CREATE INDEX statements
** for all indexes that were tested (for all SQL statements). The iStmt
** parameter is ignored for EXPERT_REPORT_CANDIDATES calls.
const char *sqlite3_expert_report(sqlite3expert*, int iStmt, int eReport);
** Values for the third argument passed to sqlite3_expert_report().
#define EXPERT_REPORT_SQL 1
#define EXPERT_REPORT_INDEXES 2
#define EXPERT_REPORT_PLAN 3
#define EXPERT_REPORT_CANDIDATES 4
** Free an (sqlite3expert*) handle and all associated resources. There
** should be one call to this function for each successful call to