path: root/src/common/sql.c

// Copyright (c) Athena Dev Teams - Licensed under GNU GPL
// For more information, see LICENCE in the main folder

#include "../common/cbasetypes.h"
#include "../common/malloc.h"
#include "../common/showmsg.h"
#include "../common/strlib.h"
#include "../common/timer.h"
#include "sql.h"

#ifdef WIN32
#include <winsock2.h>
#endif
#include <mysql.h>
#include <string.h>// strlen/strnlen/memcpy/memset
#include <stdlib.h>// strtoul



/// Sql handle
struct Sql
{
	StringBuf buf;
	MYSQL handle;
	MYSQL_RES* result;
	MYSQL_ROW row;
	unsigned long* lengths;
	int keepalive;
};



// Column length receiver.
// Takes care of the possible size missmatch between uint32 and unsigned long.
struct s_column_length
{
	uint32* out_length;
	unsigned long length;
};
typedef struct s_column_length s_column_length;



/// Sql statement
struct SqlStmt
{
	StringBuf buf;
	MYSQL_STMT* stmt;
	MYSQL_BIND* params;
	MYSQL_BIND* columns;
	s_column_length* column_lengths;
	size_t max_params;
	size_t max_columns;
	bool bind_params;
	bool bind_columns;
};



///////////////////////////////////////////////////////////////////////////////
// Sql Handle
///////////////////////////////////////////////////////////////////////////////



/// Allocates and initializes a new Sql handle.
Sql* Sql_Malloc(void)
{
	Sql* self;

	CREATE(self, Sql, 1);
	mysql_init(&self->handle);
	StringBuf_Init(&self->buf);
	self->lengths = NULL;
	self->result = NULL;
	self->keepalive = INVALID_TIMER;

	return self;
}



static int Sql_P_Keepalive(Sql* self);

/// Establishes a connection.
int Sql_Connect(Sql* self, const char* user, const char* passwd, const char* host, uint16 port, const char* db)
{
	if( self == NULL )
		return SQL_ERROR;

	StringBuf_Clear(&self->buf);
	if( !mysql_real_connect(&self->handle, host, user, passwd, db, (unsigned int)port, NULL/*unix_socket*/, 0/*clientflag*/) )
	{
		ShowSQL("%s\n", mysql_error(&self->handle));
		return SQL_ERROR;
	}

	self->keepalive = Sql_P_Keepalive(self);
	if( self->keepalive == INVALID_TIMER )
	{
		ShowSQL("Failed to establish keepalive for DB connection!\n");
		return SQL_ERROR;
	}

	return SQL_SUCCESS;
}



/// Retrieves the timeout of the connection.
int Sql_GetTimeout(Sql* self, uint32* out_timeout)
{
	if( self && out_timeout && SQL_SUCCESS == Sql_Query(self, "SHOW VARIABLES LIKE 'wait_timeout'") )
	{
		char* data;
		size_t len;
		if( SQL_SUCCESS == Sql_NextRow(self) &&
			SQL_SUCCESS == Sql_GetData(self, 1, &data, &len) )
		{
			*out_timeout = (uint32)strtoul(data, NULL, 10);
			Sql_FreeResult(self);
			return SQL_SUCCESS;
		}
		Sql_FreeResult(self);
	}
	return SQL_ERROR;
}



/// Retrieves the name of the columns of a table into out_buf, with the separator after each name.
int Sql_GetColumnNames(Sql* self, const char* table, char* out_buf, size_t buf_len, char sep)
{
	char* data;
	size_t len;
	size_t off = 0;

	if( self == NULL || SQL_ERROR == Sql_Query(self, "EXPLAIN `%s`", table) )
		return SQL_ERROR;

	out_buf[off] = '\0';
	while( SQL_SUCCESS == Sql_NextRow(self) && SQL_SUCCESS == Sql_GetData(self, 0, &data, &len) )
	{
		len = strnlen(data, len);
		if( off + len + 2 > buf_len )
		{
			ShowDebug("Sql_GetColumns: output buffer is too small\n");
			*out_buf = '\0';
			return SQL_ERROR;
		}
		memcpy(out_buf+off, data, len);
		off += len;
		out_buf[off++] = sep;
	}
	out_buf[off] = '\0';
	Sql_FreeResult(self);
	return SQL_SUCCESS;
}



/// Changes the encoding of the connection.
int Sql_SetEncoding(Sql* self, const char* encoding)
{
	if( self && mysql_set_character_set(&self->handle, encoding) == 0 )
		return SQL_SUCCESS;
	return SQL_ERROR;
}



/// Pings the connection.
int Sql_Ping(Sql* self)
{
	if( self && mysql_ping(&self->handle) == 0 )
		return SQL_SUCCESS;
	return SQL_ERROR;
}



/// Wrapper function for Sql_Ping.
///
/// @private
static int Sql_P_KeepaliveTimer(int tid, unsigned int tick, int id, intptr data)
{
	Sql* self = (Sql*)data;
	ShowInfo("Pinging SQL server to keep connection alive...\n");
	Sql_Ping(self);
	return 0;
}



/// Establishes keepalive (periodic ping) on the connection.
///
/// @return the keepalive timer id, or INVALID_TIMER
/// @private
static int Sql_P_Keepalive(Sql* self)
{
	uint32 timeout, ping_interval;

	// set a default value first
	timeout = 28800; // 8 hours

	// request the timeout value from the mysql server
	Sql_GetTimeout(self, &timeout);

	if( timeout < 60 )
		timeout = 60;

	// establish keepalive
	ping_interval = timeout - 30; // 30-second reserve
	//add_timer_func_list(Sql_P_KeepaliveTimer, "Sql_P_KeepaliveTimer");
	return add_timer_interval(gettick() + ping_interval*1000, Sql_P_KeepaliveTimer, 0, (intptr)self, ping_interval*1000);
}



/// Escapes a string.
size_t Sql_EscapeString(Sql* self, char *out_to, const char *from)
{
	if( self )
		return (size_t)mysql_real_escape_string(&self->handle, out_to, from, (unsigned long)strlen(from));
	else
		return (size_t)mysql_escape_string(out_to, from, (unsigned long)strlen(from));
}



/// Escapes a string.
size_t Sql_EscapeStringLen(Sql* self, char *out_to, const char *from, size_t from_len)
{
	if( self )
		return (size_t)mysql_real_escape_string(&self->handle, out_to, from, (unsigned long)from_len);
	else
		return (size_t)mysql_escape_string(out_to, from, (unsigned long)from_len);
}



/// Executes a query.
int Sql_Query(Sql* self, const char* query, ...)
{
	int res;
	va_list args;

	va_start(args, query);
	res = Sql_QueryV(self, query, args);
	va_end(args);

	return res;
}



/// Executes a query.
int Sql_QueryV(Sql* self, const char* query, va_list args)
{
	if( self == NULL )
		return SQL_ERROR;

	Sql_FreeResult(self);
	StringBuf_Clear(&self->buf);
	StringBuf_Vprintf(&self->buf, query, args);
	if( mysql_real_query(&self->handle, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
	{
		ShowSQL("DB error - %s\n", mysql_error(&self->handle));
		return SQL_ERROR;
	}
	self->result = mysql_store_result(&self->handle);
	if( mysql_errno(&self->handle) != 0 )
	{
		ShowSQL("DB error - %s\n", mysql_error(&self->handle));
		return SQL_ERROR;
	}
	return SQL_SUCCESS;
}



/// Executes a query.
int Sql_QueryStr(Sql* self, const char* query)
{
	if( self == NULL )
		return SQL_ERROR;

	Sql_FreeResult(self);
	StringBuf_Clear(&self->buf);
	StringBuf_AppendStr(&self->buf, query);
	if( mysql_real_query(&self->handle, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
	{
		ShowSQL("DB error - %s\n", mysql_error(&self->handle));
		return SQL_ERROR;
	}
	self->result = mysql_store_result(&self->handle);
	if( mysql_errno(&self->handle) != 0 )
	{
		ShowSQL("DB error - %s\n", mysql_error(&self->handle));
		return SQL_ERROR;
	}
	return SQL_SUCCESS;
}



/// Returns the number of the AUTO_INCREMENT column of the last INSERT/UPDATE query.
uint64 Sql_LastInsertId(Sql* self)
{
	if( self )
		return (uint64)mysql_insert_id(&self->handle);
	else
		return 0;
}



/// Returns the number of columns in each row of the result.
uint32 Sql_NumColumns(Sql* self)
{
	if( self && self->result )
		return (uint32)mysql_num_fields(self->result);
	return 0;
}



/// Returns the number of rows in the result.
uint64 Sql_NumRows(Sql* self)
{
	if( self && self->result )
		return (uint64)mysql_num_rows(self->result);
	return 0;
}



/// Fetches the next row.
int Sql_NextRow(Sql* self)
{
	if( self && self->result )
	{
		self->row = mysql_fetch_row(self->result);
		if( self->row )
		{
			self->lengths = mysql_fetch_lengths(self->result);
			return SQL_SUCCESS;
		}
		self->lengths = NULL;
		if( mysql_errno(&self->handle) == 0 )
			return SQL_NO_DATA;
	}
	return SQL_ERROR;
}



/// Gets the data of a column.
int Sql_GetData(Sql* self, size_t col, char** out_buf, size_t* out_len)
{
	if( self && self->row )
	{
		if( col < Sql_NumColumns(self) )
		{
			if( out_buf ) *out_buf = self->row[col];
			if( out_len ) *out_len = (size_t)self->lengths[col];
		}
		else
		{// out of range - ignore
			if( out_buf ) *out_buf = NULL;
			if( out_len ) *out_len = 0;
		}
		return SQL_SUCCESS;
	}
	return SQL_ERROR;
}



/// Frees the result of the query.
void Sql_FreeResult(Sql* self)
{
	if( self && self->result )
	{
		mysql_free_result(self->result);
		self->result = NULL;
		self->row = NULL;
		self->lengths = NULL;
	}
}



/// Shows debug information (last query).
void Sql_ShowDebug_(Sql* self, const char* debug_file, const unsigned long debug_line)
{
	if( self == NULL )
		ShowDebug("at %s:%lu - self is NULL\n", debug_file, debug_line);
	else if( StringBuf_Length(&self->buf) > 0 )
		ShowDebug("at %s:%lu - %s\n", debug_file, debug_line, StringBuf_Value(&self->buf));
	else
		ShowDebug("at %s:%lu\n", debug_file, debug_line);
}



/// Frees a Sql handle returned by Sql_Malloc.
void Sql_Free(Sql* self) 
{
	if( self )
	{
		Sql_FreeResult(self);
		StringBuf_Destroy(&self->buf);
		if( self->keepalive != INVALID_TIMER ) delete_timer(self->keepalive, Sql_P_KeepaliveTimer);
		aFree(self);
	}
}



///////////////////////////////////////////////////////////////////////////////
// Prepared Statements
///////////////////////////////////////////////////////////////////////////////



/// Returns the mysql integer type for the target size.
///
/// @private
static enum enum_field_types Sql_P_SizeToMysqlIntType(int sz)
{
	switch( sz )
	{
	case 1: return MYSQL_TYPE_TINY;
	case 2: return MYSQL_TYPE_SHORT;
	case 4: return MYSQL_TYPE_LONG;
	case 8: return MYSQL_TYPE_LONGLONG;
	default:
		ShowDebug("SizeToMysqlIntType: unsupported size (%d)\n", sz);
		return MYSQL_TYPE_NULL;
	}
}



/// Binds a parameter/result.
///
/// @private
static int Sql_P_BindSqlDataType(MYSQL_BIND* bind, enum SqlDataType buffer_type, void* buffer, size_t buffer_len, unsigned long* out_length, int8* out_is_null)
{
	memset(bind, 0, sizeof(MYSQL_BIND));
	switch( buffer_type )
	{
	case SQLDT_NULL: bind->buffer_type = MYSQL_TYPE_NULL;
		buffer_len = 0;// FIXME length = ? [FlavioJS]
		break;
	// fixed size
	case SQLDT_UINT8: bind->is_unsigned = 1;
	case SQLDT_INT8: bind->buffer_type = MYSQL_TYPE_TINY;
		buffer_len = 1;
		break;
	case SQLDT_UINT16: bind->is_unsigned = 1;
	case SQLDT_INT16: bind->buffer_type = MYSQL_TYPE_SHORT;
		buffer_len = 2;
		break;
	case SQLDT_UINT32: bind->is_unsigned = 1;
	case SQLDT_INT32: bind->buffer_type = MYSQL_TYPE_LONG;
		buffer_len = 4;
		break;
	case SQLDT_UINT64: bind->is_unsigned = 1;
	case SQLDT_INT64: bind->buffer_type = MYSQL_TYPE_LONGLONG;
		buffer_len = 8;
		break;
	// platform dependent size
	case SQLDT_UCHAR: bind->is_unsigned = 1;
	case SQLDT_CHAR: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(char));
		buffer_len = sizeof(char);
		break;
	case SQLDT_USHORT: bind->is_unsigned = 1;
	case SQLDT_SHORT: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(short));
		buffer_len = sizeof(short);
		break;
	case SQLDT_UINT: bind->is_unsigned = 1;
	case SQLDT_INT: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(int));
		buffer_len = sizeof(int);
		break;
	case SQLDT_ULONG: bind->is_unsigned = 1;
	case SQLDT_LONG: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(long));
		buffer_len = sizeof(long);
		break;
	case SQLDT_ULONGLONG: bind->is_unsigned = 1;
	case SQLDT_LONGLONG: bind->buffer_type = Sql_P_SizeToMysqlIntType(sizeof(int64));
		buffer_len = sizeof(int64);
		break;
	// floating point
	case SQLDT_FLOAT: bind->buffer_type = MYSQL_TYPE_FLOAT;
		buffer_len = 4;
		break;
	case SQLDT_DOUBLE: bind->buffer_type = MYSQL_TYPE_DOUBLE;
		buffer_len = 8;
		break;
	// other
	case SQLDT_STRING:
	case SQLDT_ENUM: bind->buffer_type = MYSQL_TYPE_STRING;
		break;
	case SQLDT_BLOB: bind->buffer_type = MYSQL_TYPE_BLOB;
		break;
	default:
		ShowDebug("Sql_P_BindSqlDataType: unsupported buffer type (%d)\n", buffer_type);
		return SQL_ERROR;
	}
	bind->buffer = buffer;
	bind->buffer_length = (unsigned long)buffer_len;
	bind->length = out_length;
	bind->is_null = (my_bool*)out_is_null;
	return SQL_SUCCESS;
}



/// Prints debug information about a field (type and length).
///
/// @private
static void Sql_P_ShowDebugMysqlFieldInfo(const char* prefix, enum enum_field_types type, int is_unsigned, unsigned long length, const char* length_postfix)
{
	const char* sign = (is_unsigned ? "UNSIGNED " : "");
	const char* type_string;
	switch( type )
	{
	default:
		ShowDebug("%stype=%s%u, length=%d\n", prefix, sign, type, length);
		return;
#define SHOW_DEBUG_OF(x) case x: type_string = #x; break
	SHOW_DEBUG_OF(MYSQL_TYPE_TINY);
	SHOW_DEBUG_OF(MYSQL_TYPE_SHORT);
	SHOW_DEBUG_OF(MYSQL_TYPE_LONG);
	SHOW_DEBUG_OF(MYSQL_TYPE_INT24);
	SHOW_DEBUG_OF(MYSQL_TYPE_LONGLONG);
	SHOW_DEBUG_OF(MYSQL_TYPE_DECIMAL);
	SHOW_DEBUG_OF(MYSQL_TYPE_FLOAT);
	SHOW_DEBUG_OF(MYSQL_TYPE_DOUBLE);
	SHOW_DEBUG_OF(MYSQL_TYPE_TIMESTAMP);
	SHOW_DEBUG_OF(MYSQL_TYPE_DATE);
	SHOW_DEBUG_OF(MYSQL_TYPE_TIME);
	SHOW_DEBUG_OF(MYSQL_TYPE_DATETIME);
	SHOW_DEBUG_OF(MYSQL_TYPE_YEAR);
	SHOW_DEBUG_OF(MYSQL_TYPE_STRING);
	SHOW_DEBUG_OF(MYSQL_TYPE_VAR_STRING);
	SHOW_DEBUG_OF(MYSQL_TYPE_BLOB);
	SHOW_DEBUG_OF(MYSQL_TYPE_SET);
	SHOW_DEBUG_OF(MYSQL_TYPE_ENUM);
	SHOW_DEBUG_OF(MYSQL_TYPE_NULL);
#undef SHOW_DEBUG_TYPE_OF
	}
	ShowDebug("%stype=%s%s, length=%d%s\n", prefix, sign, type_string, length, length_postfix); 
}



/// Reports debug information about a truncated column.
///
/// @private
static void SqlStmt_P_ShowDebugTruncatedColumn(SqlStmt* self, size_t i)
{
	MYSQL_RES* meta;
	MYSQL_FIELD* field;
	MYSQL_BIND* column;

	meta = mysql_stmt_result_metadata(self->stmt);
	field = mysql_fetch_field_direct(meta, (unsigned int)i);
	ShowSQL("DB error - data of field '%s' was truncated.\n", field->name);
	ShowDebug("column - %lu\n", (unsigned long)i);
	Sql_P_ShowDebugMysqlFieldInfo("data   - ", field->type, field->flags&UNSIGNED_FLAG, self->column_lengths[i].length, "");
	column = &self->columns[i];
	if( column->buffer_type == MYSQL_TYPE_STRING )
		Sql_P_ShowDebugMysqlFieldInfo("buffer - ", column->buffer_type, column->is_unsigned, column->buffer_length, "+1(nul-terminator)");
	else
		Sql_P_ShowDebugMysqlFieldInfo("buffer - ", column->buffer_type, column->is_unsigned, column->buffer_length, "");
	mysql_free_result(meta);
}



/// Allocates and initializes a new SqlStmt handle.
SqlStmt* SqlStmt_Malloc(Sql* sql)
{
	SqlStmt* self;
	MYSQL_STMT* stmt;

	if( sql == NULL )
		return NULL;

	stmt = mysql_stmt_init(&sql->handle);
	if( stmt == NULL )
	{
		ShowSQL("DB error - %s\n", mysql_error(&sql->handle));
		return NULL;
	}
	CREATE(self, SqlStmt, 1);
	StringBuf_Init(&self->buf);
	self->stmt = stmt;
	self->params = NULL;
	self->columns = NULL;
	self->column_lengths = NULL;
	self->max_params = 0;
	self->max_columns = 0;
	self->bind_params = false;
	self->bind_columns = false;

	return self;
}



/// Prepares the statement.
int SqlStmt_Prepare(SqlStmt* self, const char* query, ...)
{
	int res;
	va_list args;

	va_start(args, query);
	res = SqlStmt_PrepareV(self, query, args);
	va_end(args);

	return res;
}



/// Prepares the statement.
int SqlStmt_PrepareV(SqlStmt* self, const char* query, va_list args)
{
	if( self == NULL )
		return SQL_ERROR;

	SqlStmt_FreeResult(self);
	StringBuf_Clear(&self->buf);
	StringBuf_Vprintf(&self->buf, query, args);
	if( mysql_stmt_prepare(self->stmt, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
	{
		ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
		return SQL_ERROR;
	}
	self->bind_params = false;

	return SQL_SUCCESS;
}



/// Prepares the statement.
int SqlStmt_PrepareStr(SqlStmt* self, const char* query)
{
	if( self == NULL )
		return SQL_ERROR;

	SqlStmt_FreeResult(self);
	StringBuf_Clear(&self->buf);
	StringBuf_AppendStr(&self->buf, query);
	if( mysql_stmt_prepare(self->stmt, StringBuf_Value(&self->buf), (unsigned long)StringBuf_Length(&self->buf)) )
	{
		ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
		return SQL_ERROR;
	}
	self->bind_params = false;

	return SQL_SUCCESS;
}



/// Returns the number of parameters in the prepared statement.
size_t SqlStmt_NumParams(SqlStmt* self)
{
	if( self )
		return (size_t)mysql_stmt_param_count(self->stmt);
	else
		return 0;
}



/// Binds a parameter to a buffer.
int SqlStmt_BindParam(SqlStmt* self, size_t idx, enum SqlDataType buffer_type, void* buffer, size_t buffer_len)
{
	if( self == NULL )
		return SQL_ERROR;

	if( !self->bind_params )
	{// initialize the bindings
		size_t i;
		size_t count;

		count = SqlStmt_NumParams(self);
		if( self->max_params < count )
		{
			self->max_params = count;
			RECREATE(self->params, MYSQL_BIND, count);
		}
		memset(self->params, 0, count*sizeof(MYSQL_BIND));
		for( i = 0; i < count; ++i )
			self->params[i].buffer_type = MYSQL_TYPE_NULL;
		self->bind_params = true;
	}
	if( idx < self->max_params )
		return Sql_P_BindSqlDataType(self->params+idx, buffer_type, buffer, buffer_len, NULL, NULL);
	else
		return SQL_SUCCESS;// out of range - ignore
}



/// Executes the prepared statement.
int SqlStmt_Execute(SqlStmt* self)
{
	if( self == NULL )
		return SQL_ERROR;

	SqlStmt_FreeResult(self);
	if( (self->bind_params && mysql_stmt_bind_param(self->stmt, self->params)) ||
		mysql_stmt_execute(self->stmt) )
	{
		ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
		return SQL_ERROR;
	}
	self->bind_columns = false;
	if( mysql_stmt_store_result(self->stmt) )// store all the data
	{
		ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
		return SQL_ERROR;
	}

	return SQL_SUCCESS;
}



/// Returns the number of the AUTO_INCREMENT column of the last INSERT/UPDATE statement.
uint64 SqlStmt_LastInsertId(SqlStmt* self)
{
	if( self )
		return (uint64)mysql_stmt_insert_id(self->stmt);
	else
		return 0;
}



/// Returns the number of columns in each row of the result.
size_t SqlStmt_NumColumns(SqlStmt* self)
{
	if( self )
		return (size_t)mysql_stmt_field_count(self->stmt);
	else
		return 0;
}



/// Binds the result of a column to a buffer.
int SqlStmt_BindColumn(SqlStmt* self, size_t idx, enum SqlDataType buffer_type, void* buffer, size_t buffer_len, uint32* out_length, int8* out_is_null)
{
	if( self == NULL )
		return SQL_ERROR;

	if( buffer_type == SQLDT_STRING || buffer_type == SQLDT_ENUM )
	{
		if( buffer_len < 1 )
		{
			ShowDebug("SqlStmt_BindColumn: buffer_len(%d) is too small, no room for the nul-terminator\n", buffer_len);
			return SQL_ERROR;
		}
		--buffer_len;// nul-terminator
	}
	if( !self->bind_columns )
	{// initialize the bindings
		size_t i;
		size_t cols;

		cols = SqlStmt_NumColumns(self);
		if( self->max_columns < cols )
		{
			self->max_columns = cols;
			RECREATE(self->columns, MYSQL_BIND, cols);
			RECREATE(self->column_lengths, s_column_length, cols);
		}
		memset(self->columns, 0, cols*sizeof(MYSQL_BIND));
		memset(self->column_lengths, 0, cols*sizeof(s_column_length));
		for( i = 0; i < cols; ++i )
			self->columns[i].buffer_type = MYSQL_TYPE_NULL;
		self->bind_columns = true;
	}
	if( idx < self->max_columns )
	{
		self->column_lengths[idx].out_length = out_length;
		return Sql_P_BindSqlDataType(self->columns+idx, buffer_type, buffer, buffer_len, &self->column_lengths[idx].length, out_is_null);
	}
	else
	{
		return SQL_SUCCESS;// out of range - ignore
	}
}



/// Returns the number of rows in the result.
uint64 SqlStmt_NumRows(SqlStmt* self)
{
	if( self )
		return (uint64)mysql_stmt_num_rows(self->stmt);
	else
		return 0;
}



/// Fetches the next row.
int SqlStmt_NextRow(SqlStmt* self)
{
	int err;
	size_t i;
	size_t cols;
	MYSQL_BIND* column;
	unsigned long length;

	if( self == NULL )
		return SQL_ERROR;

	// bind columns
	if( self->bind_columns && mysql_stmt_bind_result(self->stmt, self->columns) )
		err = 1;// error binding columns
	else
		err = mysql_stmt_fetch(self->stmt);// fetch row

	// check for errors
	if( err == MYSQL_NO_DATA )
		return SQL_NO_DATA;
#if defined(MYSQL_DATA_TRUNCATED)
	// MySQL 5.0/5.1 defines and returns MYSQL_DATA_TRUNCATED [FlavioJS]
	if( err == MYSQL_DATA_TRUNCATED )
	{
		my_bool truncated;

		if( !self->bind_columns )
		{
			ShowSQL("DB error - data truncated (unknown source, columns are not bound)\n");
			return SQL_ERROR;
		}

		// find truncated column
		cols = SqlStmt_NumColumns(self);
		for( i = 0; i < cols; ++i )
		{
			column = &self->columns[i];
			column->error = &truncated;
			mysql_stmt_fetch_column(self->stmt, column, (unsigned int)i, 0);
			column->error = NULL;
			if( truncated )
			{// report truncated column
				SqlStmt_P_ShowDebugTruncatedColumn(self, i);
				return SQL_ERROR;
			}
		}
		ShowSQL("DB error - data truncated (unknown source)\n");
		return SQL_ERROR;
	}
#endif
	if( err )
	{
		ShowSQL("DB error - %s\n", mysql_stmt_error(self->stmt));
		return SQL_ERROR;
	}

	// propagate column lengths and clear unused parts of string/enum/blob buffers
	cols = SqlStmt_NumColumns(self);
	for( i = 0; i < cols; ++i )
	{
		length = self->column_lengths[i].length;
		column = &self->columns[i];
#if !defined(MYSQL_DATA_TRUNCATED)
		// MySQL 4.1/(below?) returns success even if data is truncated, so we test truncation manually [FlavioJS]
		if( column->buffer_length < length )
		{// report truncated column
			if( column->buffer_type == MYSQL_TYPE_STRING || column->buffer_type == MYSQL_TYPE_BLOB )
			{// string/enum/blob column
				SqlStmt_P_ShowDebugTruncatedColumn(self, i);
				return SQL_ERROR;
			}
			// FIXME numeric types and null [FlavioJS]
		}
#endif
		if( self->column_lengths[i].out_length )
			*self->column_lengths[i].out_length = (uint32)length;
		if( column->buffer_type == MYSQL_TYPE_STRING )
		{// clear unused part of the string/enum buffer (and nul-terminate)
			memset((char*)column->buffer + length, 0, column->buffer_length - length + 1);
		}
		else if( column->buffer_type == MYSQL_TYPE_BLOB && length < column->buffer_length )
		{// clear unused part of the blob buffer
			memset((char*)column->buffer + length, 0, column->buffer_length - length);
		}
	}

	return SQL_SUCCESS;
}



/// Frees the result of the statement execution.
void SqlStmt_FreeResult(SqlStmt* self)
{
	if( self )
		mysql_stmt_free_result(self->stmt);
}



/// Shows debug information (with statement).
void SqlStmt_ShowDebug_(SqlStmt* self, const char* debug_file, const unsigned long debug_line)
{
	if( self == NULL )
		ShowDebug("at %s:%lu -  self is NULL\n", debug_file, debug_line);
	else if( StringBuf_Length(&self->buf) > 0 )
		ShowDebug("at %s:%lu - %s\n", debug_file, debug_line, StringBuf_Value(&self->buf));
	else
		ShowDebug("at %s:%lu\n", debug_file, debug_line);
}



/// Frees a SqlStmt returned by SqlStmt_Malloc.
void SqlStmt_Free(SqlStmt* self)
{
	if( self )
	{
		SqlStmt_FreeResult(self);
		StringBuf_Destroy(&self->buf);
		mysql_stmt_close(self->stmt);
		if( self->params )
			aFree(self->params);
		if( self->columns )
		{
			aFree(self->columns);
			aFree(self->column_lengths);
		}
		aFree(self);
	}
}