MaxScale/query_classifier/qc_mysqlembedded/qc_mysqlembedded.cc

/**
 * @section LICENCE
 *
 * This file is distributed as part of the MariaDB Corporation MaxScale. It is
 * free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the
 * Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 *
 * Copyright MariaDB Corporation Ab
 *
 * @file
 *
 */

#define EMBEDDED_LIBRARY
#define MYSQL_YACC
#define MYSQL_LEX012
#define MYSQL_SERVER
#if defined(MYSQL_CLIENT)
#undef MYSQL_CLIENT
#endif

#include <my_config.h>
#include <mysql.h>
#include <my_sys.h>
#include <my_global.h>
#include <my_dbug.h>
#include <my_base.h>
#include <sql_list.h>
#include <mysqld_error.h>
#include <sql_class.h>
#include <sql_lex.h>
#include <embedded_priv.h>
#include <sql_class.h>
#include <sql_lex.h>
#include <sql_parse.h>
#include <errmsg.h>
#include <client_settings.h>
// In client_settings.h mysql_server_init and mysql_server_end are defined to
// mysql_client_plugin_init and mysql_client_plugin_deinit respectively.
// Those must be undefined, so that we here really call mysql_server_[init|end].
#undef mysql_server_init
#undef mysql_server_end
#include <set_var.h>
#include <strfunc.h>
#include <item_func.h>

#include <skygw_types.h>
#include <skygw_debug.h>
#include <log_manager.h>
#include <query_classifier.h>
#include <mysql_client_server_protocol.h>
#include <gwdirs.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>

#define MYSQL_COM_QUERY_HEADER_SIZE 5 /*< 3 bytes size, 1 sequence, 1 command */
#define MAX_QUERYBUF_SIZE 2048
typedef struct parsing_info_st
{
#if defined(SS_DEBUG)
    skygw_chk_t pi_chk_top;
#endif
    void* pi_handle; /*< parsing info object pointer */
    char* pi_query_plain_str; /*< query as plain string */
    void (*pi_done_fp)(void *); /*< clean-up function for parsing info */
#if defined(SS_DEBUG)
    skygw_chk_t pi_chk_tail;
#endif
} parsing_info_t;

#define QTYPE_LESS_RESTRICTIVE_THAN_WRITE(t) (t<QUERY_TYPE_WRITE ? true : false)

static THD* get_or_create_thd_for_parsing(MYSQL* mysql, char* query_str);
static unsigned long set_client_flags(MYSQL* mysql);
static bool create_parse_tree(THD* thd);
static uint32_t resolve_query_type(THD* thd);
static bool skygw_stmt_causes_implicit_commit(LEX* lex, int* autocommit_stmt);

static int is_autocommit_stmt(LEX* lex);
static parsing_info_t* parsing_info_init(void (*donefun)(void *));
static void parsing_info_set_plain_str(void* ptr, char* str);
/** Free THD context and close MYSQL */
static void parsing_info_done(void* ptr);
static void* skygw_get_affected_tables(void* lexptr);
static bool ensure_query_is_parsed(GWBUF* query);
static bool parse_query(GWBUF* querybuf);
static bool query_is_parsed(GWBUF* buf);


/**
 * Ensures that the query is parsed. If it is not already parsed, it
 * will be parsed.
 *
 * @return true if the query is parsed, false otherwise.
 */
bool ensure_query_is_parsed(GWBUF* query)
{
    bool parsed = query_is_parsed(query);

    if (!parsed)
    {
        parsed = parse_query(query);

        if (!parsed)
        {
            MXS_ERROR("Unable to parse query, out of resources?");
        }
    }

    return parsed;
}

qc_parse_result_t qc_parse(GWBUF* querybuf)
{
    bool parsed = ensure_query_is_parsed(querybuf);

    // Since the query is parsed using the same parser - subject to version
    // differences between the embedded library and the server - either the
    // query is valid and hence correctly parsed, or the query is invalid in
    // which case the server will also consider it invalid and reject it. So,
    // it's always ok to claim it has been parsed.
    return parsed ? QC_QUERY_PARSED : QC_QUERY_INVALID;
}

uint32_t qc_get_type(GWBUF* querybuf)
{
    MYSQL* mysql;
    uint32_t qtype = QUERY_TYPE_UNKNOWN;
    bool succp;

    ss_info_dassert(querybuf != NULL, ("querybuf is NULL"));

    if (querybuf == NULL)
    {
        succp = false;
        goto retblock;
    }

    succp = ensure_query_is_parsed(querybuf);

    /** Read thd pointer and resolve the query type with it. */
    if (succp)
    {
        parsing_info_t* pi;

        pi = (parsing_info_t*) gwbuf_get_buffer_object_data(querybuf,
                                                            GWBUF_PARSING_INFO);

        if (pi != NULL)
        {
            mysql = (MYSQL *) pi->pi_handle;

            /** Find out the query type */
            if (mysql != NULL)
            {
                qtype = resolve_query_type((THD *) mysql->thd);
            }
        }
    }

retblock:
    return qtype;
}

/**
 * Create parsing info and try to parse the query included in the query buffer.
 * Store pointer to created parse_tree_t object to buffer.
 *
 * @param querybuf buffer including the query and possibly the parsing information
 *
 * @return true if succeed, false otherwise
 */
static bool parse_query(GWBUF* querybuf)
{
    bool succp;
    THD* thd;
    uint8_t* data;
    size_t len;
    char* query_str = NULL;
    parsing_info_t* pi;

    CHK_GWBUF(querybuf);
    /** Do not parse without releasing previous parse info first */
    ss_dassert(!query_is_parsed(querybuf));

    if (querybuf == NULL || query_is_parsed(querybuf))
    {
        MXS_ERROR("Query is NULL (%p) or query is already parsed.", querybuf);
        return false;
    }

    /** Create parsing info */
    pi = parsing_info_init(parsing_info_done);

    if (pi == NULL)
    {
        MXS_ERROR("Parsing info initialization failed.");
        succp = false;
        goto retblock;
    }

    /** Extract query and copy it to different buffer */
    data = (uint8_t*) GWBUF_DATA(querybuf);
    len = MYSQL_GET_PACKET_LEN(data) - 1; /*< distract 1 for packet type byte */


    if (len < 1 || len >= ~((size_t) 0) - 1 || (query_str = (char *) malloc(len + 1)) == NULL)
    {
        /** Free parsing info data */
        MXS_ERROR("Length (%lu) is 0 or query string allocation failed (%p). Buffer is %lu bytes.",
                  len, query_str, GWBUF_LENGTH(querybuf));
        parsing_info_done(pi);
        succp = false;
        goto retblock;
    }

    memcpy(query_str, &data[5], len);
    memset(&query_str[len], 0, 1);
    parsing_info_set_plain_str(pi, query_str);

    /** Get one or create new THD object to be use in parsing */
    thd = get_or_create_thd_for_parsing((MYSQL *) pi->pi_handle, query_str);

    if (thd == NULL)
    {
        MXS_ERROR("THD creation failed.");
        /** Free parsing info data */
        parsing_info_done(pi);
        succp = false;
        goto retblock;
    }

    /**
     * Create parse_tree inside thd.
     * thd and lex are readable even if creating parse tree fails.
     */
    create_parse_tree(thd);
    /** Add complete parsing info struct to the query buffer */
    gwbuf_add_buffer_object(querybuf,
                            GWBUF_PARSING_INFO,
                            (void *) pi,
                            parsing_info_done);

    succp = true;
retblock:
    return succp;
}

/**
 * If buffer has non-NULL gwbuf_parsing_info it is parsed and it has parsing
 * information included.
 *
 * @param buf buffer being examined
 *
 * @return true or false
 */
static bool query_is_parsed(GWBUF* buf)
{
    CHK_GWBUF(buf);
    return (buf != NULL && GWBUF_IS_PARSED(buf));
}

/**
 * Create a thread context, thd, init embedded server, connect to it, and allocate
 * query to thd.
 *
 * Parameters:
 * @param mysql         Database handle
 *
 * @param query_str     Query in plain txt string
 *
 * @return Thread context pointer
 *
 */
static THD* get_or_create_thd_for_parsing(MYSQL* mysql, char* query_str)
{
    THD* thd = NULL;
    unsigned long client_flags;
    char* db = mysql->options.db;
    bool failp = FALSE;
    size_t query_len;

    ss_info_dassert(mysql != NULL, ("mysql is NULL"));
    ss_info_dassert(query_str != NULL, ("query_str is NULL"));

    query_len = strlen(query_str);
    client_flags = set_client_flags(mysql);

    /** Get THD.
     * NOTE: Instead of creating new every time, THD instance could
     * be get from a pool of them.
     */
    thd = (THD *) create_embedded_thd(client_flags);

    if (thd == NULL)
    {
        MXS_ERROR("Failed to create thread context for parsing.");
        goto return_thd;
    }

    mysql->thd = thd;
    init_embedded_mysql(mysql, client_flags);
    failp = check_embedded_connection(mysql, db);

    if (failp)
    {
        MXS_ERROR("Call to check_embedded_connection failed.");
        goto return_err_with_thd;
    }

    thd->clear_data_list();

    /** Check that we are calling the client functions in right order */
    if (mysql->status != MYSQL_STATUS_READY)
    {
        set_mysql_error(mysql, CR_COMMANDS_OUT_OF_SYNC, unknown_sqlstate);
        MXS_ERROR("Invalid status %d in embedded server.",
                  mysql->status);
        goto return_err_with_thd;
    }

    /** Clear result variables */
    thd->current_stmt = NULL;
    thd->store_globals();
    /**
     * We have to call free_old_query before we start to fill mysql->fields
     * for new query. In the case of embedded server we collect field data
     * during query execution (not during data retrieval as it is in remote
     * client). So we have to call free_old_query here
     */
    free_old_query(mysql);
    thd->extra_length = query_len;
    thd->extra_data = query_str;
    alloc_query(thd, query_str, query_len);
    goto return_thd;

return_err_with_thd:
    (*mysql->methods->free_embedded_thd)(mysql);
    thd = 0;
    mysql->thd = 0;
return_thd:
    return thd;
}

/**
 * @node  Set client flags. This is copied from libmysqld.c:mysql_real_connect
 *
 * Parameters:
 * @param mysql - <usage>
 *          <description>
 *
 * @return
 *
 *
 * @details (write detailed description here)
 *
 */
static unsigned long set_client_flags(MYSQL* mysql)
{
    unsigned long f = 0;

    f |= mysql->options.client_flag;

    /* Send client information for access check */
    f |= CLIENT_CAPABILITIES;

    if (f & CLIENT_MULTI_STATEMENTS)
    {
        f |= CLIENT_MULTI_RESULTS;
    }

    /**
     * No compression in embedded as we don't send any data,
     * and no pluggable auth, as we cannot do a client-server dialog
     */
    f &= ~(CLIENT_COMPRESS | CLIENT_PLUGIN_AUTH);

    if (mysql->options.db != NULL)
    {
        f |= CLIENT_CONNECT_WITH_DB;
    }

    return f;
}

static bool create_parse_tree(THD* thd)
{
    Parser_state parser_state;
    bool failp = FALSE;
    const char* virtual_db = "skygw_virtual";

    if (parser_state.init(thd, thd->query(), thd->query_length()))
    {
        failp = TRUE;
        goto return_here;
    }

    thd->reset_for_next_command();

    /**
     * Set some database to thd so that parsing won't fail because of
     * missing database. Then parse.
     */
    failp = thd->set_db(virtual_db, strlen(virtual_db));

    if (failp)
    {
        MXS_ERROR("Failed to set database in thread context.");
    }

    failp = parse_sql(thd, &parser_state, NULL);

    if (failp)
    {
        MXS_DEBUG("%lu [readwritesplit:create_parse_tree] failed to "
                  "create parse tree.",
                  pthread_self());
    }

return_here:
    return failp;
}

/**
 * Detect query type by examining parsed representation of it.
 *
 * @param thd   MariaDB thread context.
 *
 * @return Copy of query type value.
 *
 *
 * @details Query type is deduced by checking for certain properties
 * of them. The order is essential. Some SQL commands have multiple
 * flags set and changing the order in which flags are tested,
 * the resulting type may be different.
 *
 */
static uint32_t resolve_query_type(THD* thd)
{
    qc_query_type_t qtype = QUERY_TYPE_UNKNOWN;
    uint32_t type = QUERY_TYPE_UNKNOWN;
    int set_autocommit_stmt = -1; /*< -1 no, 0 disable, 1 enable */
    LEX* lex;
    Item* item;
    /**
     * By default, if sql_log_bin, that is, recording data modifications
     * to binary log, is disabled, gateway treats operations normally.
     * Effectively nothing is replicated.
     * When force_data_modify_op_replication is TRUE, gateway distributes
     * all write operations to all nodes.
     */
#if defined(NOT_IN_USE)
    bool force_data_modify_op_replication;
    force_data_modify_op_replication = FALSE;
#endif /* NOT_IN_USE */
    ss_info_dassert(thd != NULL, ("thd is NULL\n"));

    lex = thd->lex;

    /** SELECT ..INTO variable|OUTFILE|DUMPFILE */
    if (lex->result != NULL)
    {
        type = QUERY_TYPE_GSYSVAR_WRITE;
        goto return_qtype;
    }

    if (skygw_stmt_causes_implicit_commit(lex, &set_autocommit_stmt))
    {
        if (MXS_LOG_PRIORITY_IS_ENABLED(LOG_INFO))
        {
            if (sql_command_flags[lex->sql_command] &
                CF_IMPLICT_COMMIT_BEGIN)
            {
                MXS_INFO("Implicit COMMIT before executing the next command.");
            }
            else if (sql_command_flags[lex->sql_command] &
                     CF_IMPLICIT_COMMIT_END)
            {
                MXS_INFO("Implicit COMMIT after executing the next command.");
            }
        }

        if (set_autocommit_stmt == 1)
        {
            type |= QUERY_TYPE_ENABLE_AUTOCOMMIT;
        }

        type |= QUERY_TYPE_COMMIT;
    }

    if (set_autocommit_stmt == 0)
    {
        if (MXS_LOG_PRIORITY_IS_ENABLED(LOG_INFO))
        {
            MXS_INFO("Disable autocommit : implicit START TRANSACTION"
                     " before executing the next command.");
        }

        type |= QUERY_TYPE_DISABLE_AUTOCOMMIT;
        type |= QUERY_TYPE_BEGIN_TRX;
    }

    if (lex->option_type == OPT_GLOBAL)
    {
        /**
         * SHOW syntax http://dev.mysql.com/doc/refman/5.6/en/show.html
         */
        if (lex->sql_command == SQLCOM_SHOW_VARIABLES)
        {
            type |= QUERY_TYPE_GSYSVAR_READ;
        }
            /**
             * SET syntax http://dev.mysql.com/doc/refman/5.6/en/set-statement.html
             */
        else if (lex->sql_command == SQLCOM_SET_OPTION)
        {
            type |= QUERY_TYPE_GSYSVAR_WRITE;
        }

            /*
             * SHOW GLOBAL STATUS - Route to master
             */
        else if (lex->sql_command == SQLCOM_SHOW_STATUS)
        {
            type = QUERY_TYPE_WRITE;
        }
            /**
             * REVOKE ALL, ASSIGN_TO_KEYCACHE,
             * PRELOAD_KEYS, FLUSH, RESET, CREATE|ALTER|DROP SERVER
             */

        else
        {
            type |= QUERY_TYPE_GSYSVAR_WRITE;
        }

        goto return_qtype;
    }
    else if (lex->option_type == OPT_SESSION)
    {
        /**
         * SHOW syntax http://dev.mysql.com/doc/refman/5.6/en/show.html
         */
        if (lex->sql_command == SQLCOM_SHOW_VARIABLES)
        {
            type |= QUERY_TYPE_SYSVAR_READ;
        }
            /**
             * SET syntax http://dev.mysql.com/doc/refman/5.6/en/set-statement.html
             */
        else if (lex->sql_command == SQLCOM_SET_OPTION)
        {
            /** Either user- or system variable write */
            type |= QUERY_TYPE_GSYSVAR_WRITE;
        }

        goto return_qtype;
    }

    /**
     * 1:ALTER TABLE, TRUNCATE, REPAIR, OPTIMIZE, ANALYZE, CHECK.
     * 2:CREATE|ALTER|DROP|TRUNCATE|RENAME TABLE, LOAD, CREATE|DROP|ALTER DB,
     *   CREATE|DROP INDEX, CREATE|DROP VIEW, CREATE|DROP TRIGGER,
     *   CREATE|ALTER|DROP EVENT, UPDATE, INSERT, INSERT(SELECT),
     *   DELETE, REPLACE, REPLACE(SELECT), CREATE|RENAME|DROP USER,
     *   GRANT, REVOKE, OPTIMIZE, CREATE|ALTER|DROP FUNCTION|PROCEDURE,
     *   CREATE SPFUNCTION, INSTALL|UNINSTALL PLUGIN
     */
    if (is_log_table_write_query(lex->sql_command) ||
        is_update_query(lex->sql_command))
    {
#if defined(NOT_IN_USE)

        if (thd->variables.sql_log_bin == 0 &&
            force_data_modify_op_replication)
        {
            /** Not replicated */
            type |= QUERY_TYPE_SESSION_WRITE;
        }
        else
#endif /* NOT_IN_USE */
        {
            /** Written to binlog, that is, replicated except tmp tables */
            type |= QUERY_TYPE_WRITE; /*< to master */

            if (lex->sql_command == SQLCOM_CREATE_TABLE &&
                (lex->create_info.options & HA_LEX_CREATE_TMP_TABLE))
            {
                type |= QUERY_TYPE_CREATE_TMP_TABLE; /*< remember in router */
            }
        }
    }

    /** Try to catch session modifications here */
    switch (lex->sql_command)
    {
    case SQLCOM_EMPTY_QUERY:
        type |= QUERY_TYPE_READ;
        break;

    case SQLCOM_CHANGE_DB:
        type |= QUERY_TYPE_SESSION_WRITE;
        break;

    case SQLCOM_DEALLOCATE_PREPARE:
        type |= QUERY_TYPE_WRITE;
        break;

    case SQLCOM_SELECT:
    case SQLCOM_SHOW_SLAVE_STAT:
        type |= QUERY_TYPE_READ;
        break;

    case SQLCOM_CALL:
        type |= QUERY_TYPE_WRITE;
        break;

    case SQLCOM_BEGIN:
        type |= QUERY_TYPE_BEGIN_TRX;
        goto return_qtype;
        break;

    case SQLCOM_COMMIT:
        type |= QUERY_TYPE_COMMIT;
        goto return_qtype;
        break;

    case SQLCOM_ROLLBACK:
        type |= QUERY_TYPE_ROLLBACK;
        goto return_qtype;
        break;

    case SQLCOM_PREPARE:
        type |= QUERY_TYPE_PREPARE_NAMED_STMT;
        goto return_qtype;
        break;

    case SQLCOM_SHOW_DATABASES:
        type |= QUERY_TYPE_SHOW_DATABASES;
        goto return_qtype;
        break;

    case SQLCOM_SHOW_FIELDS:
        type |= QUERY_TYPE_READ;
        break;

    case SQLCOM_SHOW_TABLES:
        type |= QUERY_TYPE_SHOW_TABLES;
        goto return_qtype;
        break;

    default:
        type |= QUERY_TYPE_WRITE;
        break;
    }

#if defined(UPDATE_VAR_SUPPORT)

    if (QTYPE_LESS_RESTRICTIVE_THAN_WRITE(type))
#endif
        // TODO: This test is meaningless, since at this point
        // TODO: qtype (not type) is QUERY_TYPE_UNKNOWN.
        if (QUERY_IS_TYPE(qtype, QUERY_TYPE_UNKNOWN) ||
            QUERY_IS_TYPE(qtype, QUERY_TYPE_LOCAL_READ) ||
            QUERY_IS_TYPE(qtype, QUERY_TYPE_READ) ||
            QUERY_IS_TYPE(qtype, QUERY_TYPE_USERVAR_READ) ||
            QUERY_IS_TYPE(qtype, QUERY_TYPE_SYSVAR_READ) ||
            QUERY_IS_TYPE(qtype, QUERY_TYPE_GSYSVAR_READ))
        {
            /**
             * These values won't change qtype more restrictive than write.
             * UDFs and procedures could possibly cause session-wide write,
             * but unless their content is replicated this is a limitation
             * of this implementation.
             * In other words : UDFs and procedures are not allowed to
             * perform writes which are not replicated but need to repeat
             * in every node.
             * It is not sure if such statements exist. vraa 25.10.13
             */

            /**
             * Search for system functions, UDFs and stored procedures.
             */
            for (item = thd->free_list; item != NULL; item = item->next)
            {
                Item::Type itype;

                itype = item->type();
                MXS_DEBUG("%lu [resolve_query_type] Item %s:%s",
                          pthread_self(), item->name, STRITEMTYPE(itype));

                if (itype == Item::SUBSELECT_ITEM)
                {
                    continue;
                }
                else if (itype == Item::FUNC_ITEM)
                {
                    int func_qtype = QUERY_TYPE_UNKNOWN;
                    /**
                     * Item types:
                     * FIELD_ITEM = 0, FUNC_ITEM,
                     * SUM_FUNC_ITEM,  STRING_ITEM,    INT_ITEM,
                     * REAL_ITEM,      NULL_ITEM,      VARBIN_ITEM,
                     * COPY_STR_ITEM,  FIELD_AVG_ITEM,
                     * DEFAULT_VALUE_ITEM,             PROC_ITEM,
                     * COND_ITEM,      REF_ITEM,       FIELD_STD_ITEM,
                     * FIELD_VARIANCE_ITEM,
                     * INSERT_VALUE_ITEM,
                     * SUBSELECT_ITEM, ROW_ITEM,       CACHE_ITEM,
                     * TYPE_HOLDER,    PARAM_ITEM,
                     * TRIGGER_FIELD_ITEM,             DECIMAL_ITEM,
                     * XPATH_NODESET,  XPATH_NODESET_CMP,
                     * VIEW_FIXER_ITEM,
                     * EXPR_CACHE_ITEM == 27
                     **/

                    Item_func::Functype ftype;
                    ftype = ((Item_func*) item)->functype();

                    /**
                     * Item_func types:
                     *
                     * UNKNOWN_FUNC = 0,EQ_FUNC,      EQUAL_FUNC,
                     * NE_FUNC,         LT_FUNC,      LE_FUNC,
                     * GE_FUNC,         GT_FUNC,      FT_FUNC,
                     * LIKE_FUNC == 10, ISNULL_FUNC,  ISNOTNULL_FUNC,
                     * COND_AND_FUNC,   COND_OR_FUNC, XOR_FUNC,
                     * BETWEEN,         IN_FUNC,
                     * MULT_EQUAL_FUNC, INTERVAL_FUNC,
                     * ISNOTNULLTEST_FUNC == 20,
                     * SP_EQUALS_FUNC,  SP_DISJOINT_FUNC,
                     * SP_INTERSECTS_FUNC,
                     * SP_TOUCHES_FUNC, SP_CROSSES_FUNC,
                     * SP_WITHIN_FUNC,  SP_CONTAINS_FUNC,
                     * SP_OVERLAPS_FUNC,
                     * SP_STARTPOINT,   SP_ENDPOINT == 30,
                     * SP_EXTERIORRING, SP_POINTN,    SP_GEOMETRYN,
                     * SP_INTERIORRINGN,NOT_FUNC,     NOT_ALL_FUNC,
                     * NOW_FUNC,        TRIG_COND_FUNC,
                     * SUSERVAR_FUNC,   GUSERVAR_FUNC == 40,
                     * COLLATE_FUNC,    EXTRACT_FUNC,
                     * CHAR_TYPECAST_FUNC,
                     * FUNC_SP,         UDF_FUNC,     NEG_FUNC,
                     * GSYSVAR_FUNC == 47
                     **/
                    switch (ftype)
                    {
                    case Item_func::FUNC_SP:
                        /**
                         * An unknown (for maxscale) function / sp
                         * belongs to this category.
                         */
                        func_qtype |= QUERY_TYPE_WRITE;
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "functype FUNC_SP, stored proc "
                                  "or unknown function.",
                                  pthread_self());
                        break;

                    case Item_func::UDF_FUNC:
                        func_qtype |= QUERY_TYPE_WRITE;
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "functype UDF_FUNC, user-defined "
                                  "function.",
                                  pthread_self());
                        break;

                    case Item_func::NOW_FUNC:
                        // If this is part of a CREATE TABLE, then local read is not
                        // applicable.
                        if (lex->sql_command != SQLCOM_CREATE_TABLE)
                        {
                            func_qtype |= QUERY_TYPE_LOCAL_READ;
                            MXS_DEBUG("%lu [resolve_query_type] "
                                      "functype NOW_FUNC, could be "
                                      "executed in MaxScale.",
                                      pthread_self());
                        }
                        break;

                        /** System session variable */
                    case Item_func::GSYSVAR_FUNC:
                        func_qtype |= QUERY_TYPE_SYSVAR_READ;
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "functype GSYSVAR_FUNC, system "
                                  "variable read.",
                                  pthread_self());
                        break;

                        /** User-defined variable read */
                    case Item_func::GUSERVAR_FUNC:
                        func_qtype |= QUERY_TYPE_USERVAR_READ;
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "functype GUSERVAR_FUNC, user "
                                  "variable read.",
                                  pthread_self());
                        break;

                        /** User-defined variable modification */
                    case Item_func::SUSERVAR_FUNC:
                        /**
                         * Really it is user variable but we
                         * don't separate sql variables atm.
                         * 15.9.14
                         */
                        func_qtype |= QUERY_TYPE_GSYSVAR_WRITE;
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "functype SUSERVAR_FUNC, user "
                                  "variable write.",
                                  pthread_self());
                        break;

                    case Item_func::UNKNOWN_FUNC:

                        if (((Item_func*) item)->func_name() != NULL &&
                            strcmp((char*) ((Item_func*) item)->func_name(), "last_insert_id") == 0)
                        {
                            func_qtype |= QUERY_TYPE_MASTER_READ;
                        }
                        else
                        {
                            func_qtype |= QUERY_TYPE_READ;
                        }

                        /**
                         * Many built-in functions are of this
                         * type, for example, rand(), soundex(),
                         * repeat() .
                         */
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "functype UNKNOWN_FUNC, "
                                  "typically some system function.",
                                  pthread_self());
                        break;

                    default:
                        MXS_DEBUG("%lu [resolve_query_type] "
                                  "Functype %d.",
                                  pthread_self(),
                                  ftype);
                        break;
                    } /**< switch */

                    /**< Set new query type */
                    type |= func_qtype;
                }

#if defined(UPDATE_VAR_SUPPORT)

                /**
                 * Write is as restrictive as it gets due functions,
                 * so break.
                 */
                if ((type & QUERY_TYPE_WRITE) == QUERY_TYPE_WRITE)
                {
                    break;
                }

#endif
            } /**< for */
        } /**< if */

return_qtype:
    qtype = (qc_query_type_t) type;
    return qtype;
}

/**
 * Checks if statement causes implicit COMMIT.
 * autocommit_stmt gets values 1, 0 or -1 if stmt is enable, disable or
 * something else than autocommit.
 *
 * @param lex           Parse tree
 * @param autocommit_stmt   memory address for autocommit status
 *
 * @return true if statement causes implicit commit and false otherwise
 */
static bool skygw_stmt_causes_implicit_commit(LEX* lex, int* autocommit_stmt)
{
    bool succp;

    if (!(sql_command_flags[lex->sql_command] & CF_AUTO_COMMIT_TRANS))
    {
        succp = false;
        goto return_succp;
    }

    switch (lex->sql_command)
    {
    case SQLCOM_DROP_TABLE:
        succp = !(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE);
        break;

    case SQLCOM_ALTER_TABLE:
    case SQLCOM_CREATE_TABLE:
        /* If CREATE TABLE of non-temporary table, do implicit commit */
        succp = !(lex->create_info.options & HA_LEX_CREATE_TMP_TABLE);
        break;

    case SQLCOM_SET_OPTION:
        if ((*autocommit_stmt = is_autocommit_stmt(lex)) == 1)
        {
            succp = true;
        }
        else
        {
            succp = false;
        }

        break;

    default:
        succp = true;
        break;
    }

return_succp:
    return succp;
}

/**
 * Finds out if stmt is SET autocommit
 * and if the new value matches with the enable_cmd argument.
 *
 * @param lex   parse tree
 *
 * @return 1, 0, or -1 if command was:
 * enable, disable, or not autocommit, respectively.
 */
static int is_autocommit_stmt(LEX* lex)
{
    struct list_node* node;
    set_var* setvar;
    int rc = -1;
    static char target[8]; /*< for converted string */
    Item* item = NULL;

    node = lex->var_list.first_node();
    setvar = (set_var*) node->info;

    if (setvar == NULL)
    {
        goto return_rc;
    }

    do /*< Search for the last occurrence of 'autocommit' */
    {
        if ((sys_var*) setvar->var == Sys_autocommit_ptr)
        {
            item = setvar->value;
        }

        node = node->next;
    }
    while ((setvar = (set_var*) node->info) != NULL);

    if (item != NULL) /*< found autocommit command */
    {
        if (item->type() == Item::INT_ITEM) /*< '0' or '1' */
        {
            rc = item->val_int();

            if (rc > 1 || rc < 0)
            {
                rc = -1;
            }
        }
        else if (item->type() == Item::STRING_ITEM) /*< 'on' or 'off' */
        {
            String str(target, sizeof (target), system_charset_info);
            String* res = item->val_str(&str);

            if ((rc = find_type(&bool_typelib, res->ptr(), res->length(), false)))
            {
                ss_dassert(rc >= 0 && rc <= 2);
                /**
                 * rc is the position of matchin string in
                 * typelib's value array.
                 * 1=OFF, 2=ON.
                 */
                rc -= 1;
            }
        }
    }

return_rc:
    return rc;
}

#if defined(NOT_USED)

char* qc_get_stmtname(GWBUF* buf)
{
    MYSQL* mysql;

    if (buf == NULL ||
        buf->gwbuf_bufobj == NULL ||
        buf->gwbuf_bufobj->bo_data == NULL ||
        (mysql = (MYSQL *) ((parsing_info_t *) buf->gwbuf_bufobj->bo_data)->pi_handle) == NULL ||
        mysql->thd == NULL ||
        (THD *) (mysql->thd))->lex == NULL ||
        (THD *) (mysql->thd))->lex->prepared_stmt_name == NULL)
        {
            return NULL;
        }

    return ((THD *) (mysql->thd))->lex->prepared_stmt_name.str;
}
#endif

/**
 * Get the parse tree from parsed querybuf.
 * @param querybuf  The parsed GWBUF
 *
 * @return Pointer to the LEX struct or NULL if an error occurred or the query
 * was not parsed
 */
LEX* get_lex(GWBUF* querybuf)
{

    parsing_info_t* pi;
    MYSQL* mysql;
    THD* thd;

    if (querybuf == NULL || !GWBUF_IS_PARSED(querybuf))
    {
        return NULL;
    }

    pi = (parsing_info_t *) gwbuf_get_buffer_object_data(querybuf, GWBUF_PARSING_INFO);

    if (pi == NULL)
    {
        return NULL;
    }

    if ((mysql = (MYSQL *) pi->pi_handle) == NULL ||
        (thd = (THD *) mysql->thd) == NULL)
    {
        ss_dassert(mysql != NULL && thd != NULL);
        return NULL;
    }

    return thd->lex;
}

/**
 * Finds the head of the list of tables affected by the current select statement.
 * @param thd Pointer to a valid THD
 * @return Pointer to the head of the TABLE_LIST chain or NULL in case of an error
 */
static void* skygw_get_affected_tables(void* lexptr)
{
    LEX* lex = (LEX*) lexptr;

    if (lex == NULL || lex->current_select == NULL)
    {
        ss_dassert(lex != NULL && lex->current_select != NULL);
        return NULL;
    }

    return (void*) lex->current_select->table_list.first;
}

/**
 * Reads the parsetree and lists all the affected tables and views in the query.
 * In the case of an error, the size of the table is set to zero and no memory
 * is allocated. The caller must free the allocated memory.
 *
 * @param querybuf GWBUF where the table names are extracted from
 * @param tblsize Pointer where the number of tables is written
 * @return Array of null-terminated strings with the table names
 */
char** qc_get_table_names(GWBUF* querybuf, int* tblsize, bool fullnames)
{
    LEX* lex;
    TABLE_LIST* tbl;
    int i = 0, currtblsz = 0;
    char **tables = NULL, **tmp = NULL;

    if (querybuf == NULL || tblsize == NULL)
    {
        goto retblock;
    }

    if (!ensure_query_is_parsed(querybuf))
    {
        goto retblock;
    }

    if ((lex = get_lex(querybuf)) == NULL)
    {
        goto retblock;
    }

    lex->current_select = lex->all_selects_list;

    while (lex->current_select)
    {
        tbl = (TABLE_LIST*) skygw_get_affected_tables(lex);

        while (tbl)
        {
            if (i >= currtblsz)
            {
                tmp = (char**) malloc(sizeof (char*)*(currtblsz * 2 + 1));

                if (tmp)
                {
                    if (currtblsz > 0)
                    {
                        for (int x = 0; x < currtblsz; x++)
                        {
                            tmp[x] = tables[x];
                        }

                        free(tables);
                    }

                    tables = tmp;
                    currtblsz = currtblsz * 2 + 1;
                }
            }

            if (tmp != NULL)
            {
                char *catnm = NULL;

                if (fullnames)
                {
                    if (tbl->db &&
                        (strcmp(tbl->db, "skygw_virtual") != 0) &&
                        (strcmp(tbl->table_name, "*") != 0))
                    {
                        catnm = (char*) calloc(strlen(tbl->db) +
                                               strlen(tbl->table_name) +
                                               2,
                                               sizeof (char));
                        strcpy(catnm, tbl->db);
                        strcat(catnm, ".");
                        strcat(catnm, tbl->table_name);
                    }
                }

                if (catnm)
                {
                    tables[i++] = catnm;
                }
                else
                {
                    // Sometimes the tablename is "*"; we exclude that.
                    if (strcmp(tbl->table_name, "*") != 0)
                    {
                        tables[i++] = strdup(tbl->table_name);
                    }
                }

                tbl = tbl->next_local;
            }
        } /*< while (tbl) */

        lex->current_select = lex->current_select->next_select_in_list();
    } /*< while(lex->current_select) */

retblock:

    if (tblsize)
    {
        *tblsize = i;
    }

    return tables;
}

/**
 * Extract, allocate memory and copy the name of the created table.
 * @param querybuf Buffer to use.
 * @return A pointer to the name if a table was created, otherwise NULL
 */
char* qc_get_created_table_name(GWBUF* querybuf)
{
    if (querybuf == NULL)
    {
        return NULL;
    }

    if (!ensure_query_is_parsed(querybuf))
    {
        return NULL;
    }

    char* table_name = NULL;

    LEX* lex = get_lex(querybuf);

    if (lex && (lex->sql_command == SQLCOM_CREATE_TABLE))
    {
        if (lex->create_last_non_select_table &&
            lex->create_last_non_select_table->table_name)
        {
            table_name = strdup(lex->create_last_non_select_table->table_name);
        }
    }

    return table_name;
}

/**
 * Checks whether the query is a "real" query ie. SELECT,UPDATE,INSERT,DELETE or
 * any variation of these. Queries that affect the underlying database are not
 * considered as real queries and the queries that target specific row or
 * variable data are regarded as the real queries.
 *
 * @param GWBUF to analyze
 *
 * @return true if the query is a real query, otherwise false
 */
bool qc_is_real_query(GWBUF* querybuf)
{
    bool succp;
    LEX* lex;

    if (querybuf == NULL)
    {
        succp = false;
        goto retblock;
    }

    if (!ensure_query_is_parsed(querybuf))
    {
        succp = false;
        goto retblock;
    }

    if ((lex = get_lex(querybuf)) == NULL)
    {
        succp = false;
        goto retblock;
    }

    switch (lex->sql_command)
    {
    case SQLCOM_SELECT:
        succp = lex->all_selects_list->table_list.elements > 0;
        goto retblock;
        break;

    case SQLCOM_UPDATE_MULTI:
    case SQLCOM_UPDATE:
    case SQLCOM_INSERT:
    case SQLCOM_INSERT_SELECT:
    case SQLCOM_DELETE:
    case SQLCOM_DELETE_MULTI:
    case SQLCOM_TRUNCATE:
    case SQLCOM_REPLACE:
    case SQLCOM_REPLACE_SELECT:
    case SQLCOM_PREPARE:
    case SQLCOM_EXECUTE:
        succp = true;
        goto retblock;
        break;

    default:
        succp = false;
        goto retblock;
        break;
    }

retblock:
    return succp;
}

/**
 * Checks whether the buffer contains a DROP TABLE... query.
 * @param querybuf Buffer to inspect
 * @return true if it contains the query otherwise false
 */
bool qc_is_drop_table_query(GWBUF* querybuf)
{
    bool answer = false;

    if (querybuf)
    {
        if (ensure_query_is_parsed(querybuf))
        {
            LEX* lex = get_lex(querybuf);

            answer = lex && lex->sql_command == SQLCOM_DROP_TABLE;
        }
    }

    return answer;
}

inline void add_str(char** buf, int* buflen, int* bufsize, const char* str)
{
    int isize = strlen(str) + 1;

    if (*buf == NULL || isize + *buflen >= *bufsize)
    {
        *bufsize = (*bufsize) * 2 + isize;
        char *tmp = (char*) realloc(*buf, (*bufsize) * sizeof (char));

        if (tmp == NULL)
        {
            MXS_ERROR("Error: memory reallocation failed.");
            free(*buf);
            *buf = NULL;
            *bufsize = 0;
        }

        *buf = tmp;
    }

    if (*buflen > 0)
    {
        if (*buf)
        {
            strcat(*buf, " ");
        }
    }

    if (*buf)
    {
        strcat(*buf, str);
    }

    *buflen += isize;

}

typedef enum collect_source
{
    COLLECT_SELECT,
    COLLECT_WHERE,
    COLLECT_HAVING,
    COLLECT_GROUP_BY,
} collect_source_t;


static void collect_name(Item* item, char** bufp, int* buflenp, int* bufsizep, List<Item>* excludep)
{
    const char* full_name = item->full_name();
    const char* name = strrchr(full_name, '.');

    if (!name)
    {
        // No dot found.
        name = full_name;
    }
    else
    {
        // Dot found, advance beyond it.
        ++name;
    }

    bool exclude = false;

    if (excludep)
    {
        List_iterator<Item> ilist(*excludep);
        Item* exclude_item = (Item*) ilist.next();

        for (; !exclude && (exclude_item != NULL); exclude_item = (Item*) ilist.next())
        {
            if (exclude_item->name && (strcasecmp(name, exclude_item->name) == 0))
            {
                exclude = true;
            }
        }
    }

    if (!exclude)
    {
        add_str(bufp, buflenp, bufsizep, name);
    }
}

static void collect_affected_fields(collect_source_t source,
                                    Item* item, char** bufp, int* buflenp, int* bufsizep,
                                    List<Item>* excludep)
{
    switch (item->type())
    {
    case Item::COND_ITEM:
        {
            Item_cond* cond_item = static_cast<Item_cond*>(item);
            List_iterator<Item> ilist(*cond_item->argument_list());
            item = (Item*) ilist.next();

            for (; item != NULL; item = (Item*) ilist.next())
            {
                collect_affected_fields(source, item, bufp, buflenp, bufsizep, excludep);
            }
        }
        break;

    case Item::FIELD_ITEM:
        collect_name(item, bufp, buflenp, bufsizep, excludep);
        break;

    case Item::REF_ITEM:
        {
            if (source != COLLECT_SELECT)
            {
                Item_ref* ref_item = static_cast<Item_ref*>(item);

                collect_name(item, bufp, buflenp, bufsizep, excludep);

                size_t n_items = ref_item->cols();

                for (size_t i = 0; i < n_items; ++i)
                {
                    Item* reffed_item = ref_item->element_index(i);

                    if (reffed_item != ref_item)
                    {
                        collect_affected_fields(source,
                                                ref_item->element_index(i), bufp, buflenp, bufsizep,
                                                excludep);
                    }
                }
            }
        }
        break;

    case Item::ROW_ITEM:
        {
            Item_row* row_item = static_cast<Item_row*>(item);
            size_t n_items = row_item->cols();

            for (size_t i = 0; i < n_items; ++i)
            {
                collect_affected_fields(source, row_item->element_index(i), bufp, buflenp, bufsizep,
                                        excludep);
            }
        }
        break;

    case Item::FUNC_ITEM:
    case Item::SUM_FUNC_ITEM:
        {
            Item_func* func_item = static_cast<Item_func*>(item);
            Item** items = func_item->arguments();
            size_t n_items = func_item->argument_count();

            for (size_t i = 0; i < n_items; ++i)
            {
                collect_affected_fields(source, items[i], bufp, buflenp, bufsizep, excludep);
            }
        }
        break;

    case Item::SUBSELECT_ITEM:
        {
            Item_subselect* subselect_item = static_cast<Item_subselect*>(item);

            switch (subselect_item->substype())
            {
            case Item_subselect::IN_SUBS:
            case Item_subselect::ALL_SUBS:
            case Item_subselect::ANY_SUBS:
                {
                    Item_in_subselect* in_subselect_item = static_cast<Item_in_subselect*>(item);

#if (((MYSQL_VERSION_MAJOR == 5) &&\
      ((MYSQL_VERSION_MINOR > 5) ||\
       ((MYSQL_VERSION_MINOR == 5) && (MYSQL_VERSION_PATCH >= 48))\
      )\
     ) ||\
     (MYSQL_VERSION_MAJOR >= 10)\
    )
                    if (in_subselect_item->left_expr_orig)
                    {
                        collect_affected_fields(source,
                                                in_subselect_item->left_expr_orig, bufp, buflenp, bufsizep,
                                                excludep);
                    }
#else
#pragma message "Figure out what to do with versions < 5.5.48."
#endif
                    // TODO: Anything else that needs to be looked into?
                }
                break;

            case Item_subselect::EXISTS_SUBS:
            case Item_subselect::SINGLEROW_SUBS:
                // TODO: Handle these explicitly as well.
                break;

            case Item_subselect::UNKNOWN_SUBS:
            default:
                MXS_ERROR("Unknown subselect type: %d", subselect_item->substype());
                break;
            }
        }
        break;

    default:
        break;
    }
}

/**
 * Returns all the fields that the query affects.
 * @param buf Buffer to parse
 * @return Pointer to newly allocated string or NULL if nothing was found
 */
char* qc_get_affected_fields(GWBUF* buf)
{
    LEX* lex;
    int buffsz = 0, bufflen = 0;
    char* where = NULL;
    Item* item;
    Item::Type itype;

    if (!buf)
    {
        return NULL;
    }

    if (!ensure_query_is_parsed(buf))
    {
        return NULL;
    }

    if ((lex = get_lex(buf)) == NULL)
    {
        return NULL;
    }

    lex->current_select = lex->all_selects_list;

    if ((where = (char*) malloc(sizeof (char)*1)) == NULL)
    {
        MXS_ERROR("Memory allocation failed.");
        return NULL;
    }

    *where = '\0';

    while (lex->current_select)
    {

        List_iterator<Item> ilist(lex->current_select->item_list);
        item = (Item*) ilist.next();

        for (; item != NULL; item = (Item*) ilist.next())
        {
            collect_affected_fields(COLLECT_SELECT, item, &where, &buffsz, &bufflen, NULL);
        }

        if (lex->current_select->group_list.first)
        {
            ORDER* order = lex->current_select->group_list.first;
            while (order)
            {
                Item* item = *order->item;

                collect_affected_fields(COLLECT_GROUP_BY, item, &where, &buffsz, &bufflen,
                                        &lex->current_select->item_list);

                order = order->next;
            }
        }

        if (lex->current_select->where)
        {
            collect_affected_fields(COLLECT_WHERE, lex->current_select->where, &where, &buffsz, &bufflen,
                                    &lex->current_select->item_list);
        }

        if (lex->current_select->having)
        {
            collect_affected_fields(COLLECT_HAVING, lex->current_select->having, &where, &buffsz, &bufflen,
                                    &lex->current_select->item_list);
        }

        lex->current_select = lex->current_select->next_select_in_list();
    }

    if ((lex->sql_command == SQLCOM_INSERT) ||
        (lex->sql_command == SQLCOM_INSERT_SELECT) ||
        (lex->sql_command == SQLCOM_REPLACE))
    {
        List_iterator<Item> ilist(lex->field_list);
        item = (Item*) ilist.next();

        for (; item != NULL; item = (Item*) ilist.next())
        {
            collect_affected_fields(COLLECT_SELECT, item, &where, &buffsz, &bufflen, NULL);
        }

        if (lex->insert_list)
        {
            List_iterator<Item> ilist(*lex->insert_list);
            item = (Item*) ilist.next();

            for (; item != NULL; item = (Item*) ilist.next())
            {
                collect_affected_fields(COLLECT_SELECT, item, &where, &buffsz, &bufflen, NULL);
            }
        }
    }

    return where;
}

bool qc_query_has_clause(GWBUF* buf)
{
    bool clause = false;

    if (buf)
    {
        if (ensure_query_is_parsed(buf))
        {
            LEX* lex = get_lex(buf);

            if (lex)
            {
                SELECT_LEX* current = lex->all_selects_list;

                while (current && !clause)
                {
                    if (current->where || current->having)
                    {
                        clause = true;
                    }

                    current = current->next_select_in_list();
                }
            }
        }
    }

    return clause;
}

/**
 * Create parsing information; initialize mysql handle, allocate parsing info
 * struct and set handle and free function pointer to it.
 *
 * @param donefun       pointer to free function
 *
 * @return pointer to parsing information
 */
static parsing_info_t* parsing_info_init(void (*donefun)(void *))
{
    parsing_info_t* pi = NULL;
    MYSQL* mysql;
    const char* user = "skygw";
    const char* db = "skygw";

    ss_dassert(donefun != NULL);

    /** Get server handle */
    mysql = mysql_init(NULL);

    if (mysql == NULL)
    {
        MXS_ERROR("Call to mysql_real_connect failed due %d, %s.",
                  mysql_errno(mysql),
                  mysql_error(mysql));
        ss_dassert(mysql != NULL);
        goto retblock;
    }

    /** Set methods and authentication to mysql */
    mysql_options(mysql, MYSQL_READ_DEFAULT_GROUP, "libmysqld_skygw");
    mysql_options(mysql, MYSQL_OPT_USE_EMBEDDED_CONNECTION, NULL);
    mysql->methods = &embedded_methods;
    mysql->user = my_strdup(user, MYF(0));
    mysql->db = my_strdup(db, MYF(0));
    mysql->passwd = NULL;

    pi = (parsing_info_t*) calloc(1, sizeof (parsing_info_t));

    if (pi == NULL)
    {
        mysql_close(mysql);
        goto retblock;
    }

#if defined(SS_DEBUG)
    pi->pi_chk_top = CHK_NUM_PINFO;
    pi->pi_chk_tail = CHK_NUM_PINFO;
#endif
    /** Set handle and free function to parsing info struct */
    pi->pi_handle = mysql;
    pi->pi_done_fp = donefun;

retblock:
    return pi;
}

/**
 * Free function for parsing info. Called by gwbuf_free or in case initialization
 * of parsing information fails.
 *
 * @param ptr Pointer to parsing information, cast required
 *
 * @return void
 *
 */
static void parsing_info_done(void* ptr)
{
    parsing_info_t* pi;
    THD* thd;

    if (ptr)
    {
        pi = (parsing_info_t *) ptr;

        if (pi->pi_handle != NULL)
        {
            MYSQL* mysql = (MYSQL *) pi->pi_handle;

            if (mysql->thd != NULL)
            {
                thd = (THD*) mysql->thd;
                thd->end_statement();
                (*mysql->methods->free_embedded_thd)(mysql);
                mysql->thd = NULL;
            }

            mysql_close(mysql);
        }

        /** Free plain text query string */
        if (pi->pi_query_plain_str != NULL)
        {
            free(pi->pi_query_plain_str);
        }

        free(pi);
    }
}

/**
 * Add plain text query string to parsing info.
 *
 * @param ptr   Pointer to parsing info struct, cast required
 * @param str   String to be added
 *
 * @return void
 */
static void parsing_info_set_plain_str(void* ptr, char* str)
{
    parsing_info_t* pi = (parsing_info_t *) ptr;
    CHK_PARSING_INFO(pi);

    pi->pi_query_plain_str = str;
}

/**
 * Returns an array of strings of databases that this query uses.
 * If the database isn't defined in the query, it is assumed that this query
 * only targets the current database.
 * The value of @p size is set to the number of allocated strings. The caller is
 * responsible for freeing all the allocated memory.
 * @param querybuf GWBUF containing the query
 * @param size Size of the resulting array
 * @return A new array of strings containing the database names or NULL if no
 * databases were found.
 */
char** qc_get_database_names(GWBUF* querybuf, int* size)
{
    LEX* lex;
    TABLE_LIST* tbl;
    char **databases = NULL, **tmp = NULL;
    int currsz = 0, i = 0;

    if (!querybuf)
    {
        goto retblock;
    }

    if (!ensure_query_is_parsed(querybuf))
    {
        goto retblock;
    }

    if ((lex = get_lex(querybuf)) == NULL)
    {
        goto retblock;
    }

    lex->current_select = lex->all_selects_list;

    while (lex->current_select)
    {
        tbl = lex->current_select->table_list.first;

        while (tbl)
        {
            // The database is sometimes an empty string. So as not to return
            // an array of empty strings, we need to check for that possibility.
            if ((strcmp(tbl->db, "skygw_virtual") != 0) && (*tbl->db != 0))
            {
                if (i >= currsz)
                {
                    tmp = (char**) realloc(databases,
                                           sizeof (char*)*(currsz * 2 + 1));

                    if (tmp == NULL)
                    {
                        goto retblock;
                    }

                    databases = tmp;
                    currsz = currsz * 2 + 1;
                }

                databases[i++] = strdup(tbl->db);
            }

            tbl = tbl->next_local;
        }

        lex->current_select = lex->current_select->next_select_in_list();
    }

retblock:
    *size = i;
    return databases;
}

qc_query_op_t qc_get_operation(GWBUF* querybuf)
{
    qc_query_op_t operation = QUERY_OP_UNDEFINED;

    if (querybuf)
    {
        if (ensure_query_is_parsed(querybuf))
        {
            LEX* lex = get_lex(querybuf);

            if (lex)
            {
                switch (lex->sql_command)
                {
                case SQLCOM_SELECT:
                    operation = QUERY_OP_SELECT;
                    break;

                case SQLCOM_CREATE_DB:
                case SQLCOM_CREATE_EVENT:
                case SQLCOM_CREATE_FUNCTION:
                case SQLCOM_CREATE_INDEX:
                case SQLCOM_CREATE_PROCEDURE:
                case SQLCOM_CREATE_SERVER:
                case SQLCOM_CREATE_SPFUNCTION:
                case SQLCOM_CREATE_TABLE:
                case SQLCOM_CREATE_TRIGGER:
                case SQLCOM_CREATE_USER:
                case SQLCOM_CREATE_VIEW:
                    operation = QUERY_OP_CREATE;
                    break;

                case SQLCOM_ALTER_DB:
                case SQLCOM_ALTER_DB_UPGRADE:
                case SQLCOM_ALTER_EVENT:
                case SQLCOM_ALTER_FUNCTION:
                case SQLCOM_ALTER_PROCEDURE:
                case SQLCOM_ALTER_SERVER:
                case SQLCOM_ALTER_TABLE:
                case SQLCOM_ALTER_TABLESPACE:
                    operation = QUERY_OP_ALTER;
                    break;

                case SQLCOM_UPDATE:
                case SQLCOM_UPDATE_MULTI:
                    operation = QUERY_OP_UPDATE;
                    break;

                case SQLCOM_INSERT:
                case SQLCOM_INSERT_SELECT:
                case SQLCOM_REPLACE:
                    operation = QUERY_OP_INSERT;
                    break;

                case SQLCOM_DELETE:
                case SQLCOM_DELETE_MULTI:
                    operation = QUERY_OP_DELETE;
                    break;

                case SQLCOM_TRUNCATE:
                    operation = QUERY_OP_TRUNCATE;
                    break;

                case SQLCOM_DROP_DB:
                case SQLCOM_DROP_EVENT:
                case SQLCOM_DROP_FUNCTION:
                case SQLCOM_DROP_INDEX:
                case SQLCOM_DROP_PROCEDURE:
                case SQLCOM_DROP_SERVER:
                case SQLCOM_DROP_TABLE:
                case SQLCOM_DROP_TRIGGER:
                case SQLCOM_DROP_USER:
                case SQLCOM_DROP_VIEW:
                    operation = QUERY_OP_DROP;
                    break;

                case SQLCOM_CHANGE_DB:
                    operation = QUERY_OP_CHANGE_DB;
                    break;

                case SQLCOM_LOAD:
                    operation = QUERY_OP_LOAD;
                    break;

                case SQLCOM_GRANT:
                    operation = QUERY_OP_GRANT;
                        break;

                case SQLCOM_REVOKE:
                case SQLCOM_REVOKE_ALL:
                    operation = QUERY_OP_REVOKE;
                        break;

                default:
                    operation = QUERY_OP_UNDEFINED;
                }
            }
        }
    }

    return operation;
}

namespace
{

// Do not change the order without making corresponding changes to IDX_... below.
const char* server_options[] =
{
    "MariaDB Corporation MaxScale",
    "--no-defaults",
    "--datadir=",
    "--language=",
    "--skip-innodb",
    "--default-storage-engine=myisam",
    NULL
};

const int IDX_DATADIR = 2;
const int IDX_LANGUAGE = 3;
const int N_OPTIONS = (sizeof(server_options) / sizeof(server_options[0])) - 1;

const char* server_groups[] = {
    "embedded",
    "server",
    "server",
    "embedded",
    "server",
    "server",
    NULL
};

const int OPTIONS_DATADIR_SIZE = 10 + PATH_MAX; // strlen("--datadir=");
const int OPTIONS_LANGUAGE_SIZE = 11 + PATH_MAX; // strlen("--language=");

char datadir_arg[OPTIONS_DATADIR_SIZE];
char language_arg[OPTIONS_LANGUAGE_SIZE];


void configure_options(const char* datadir, const char* langdir)
{
    int rv;

    rv = snprintf(datadir_arg, OPTIONS_DATADIR_SIZE, "--datadir=%s", datadir);
    ss_dassert(rv < OPTIONS_DATADIR_SIZE); // Ensured by create_datadir().
    server_options[IDX_DATADIR] = datadir_arg;

    rv = sprintf(language_arg, "--language=%s", langdir);
    ss_dassert(rv < OPTIONS_LANGUAGE_SIZE); // Ensured by qc_init().
    server_options[IDX_LANGUAGE] = language_arg;

    // To prevent warning of unused variable when built in release mode,
    // when ss_dassert() turns into empty statement.
    (void)rv;
}

}

bool qc_init(const char* args)
{
    bool inited = false;

    if (args)
    {
        MXS_WARNING("qc_mysqlembedded: '%s' provided as arguments, "
                    "even though no arguments are supported.", args);
    }

    if (strlen(get_langdir()) >= PATH_MAX)
    {
        fprintf(stderr, "MaxScale: error: Language path is too long: %s.", get_langdir());
    }
    else
    {
        configure_options(get_process_datadir(), get_langdir());

        int argc = N_OPTIONS;
        char** argv = const_cast<char**>(server_options);
        char** groups = const_cast<char**>(server_groups);

        int rc = mysql_library_init(argc, argv, groups);

        if (rc != 0)
        {
            MXS_ERROR("mysql_library_init() failed. Error code: %d", rc);
        }
        else
        {
#if MYSQL_VERSION_ID >= 100000
            set_malloc_size_cb(NULL);
#endif
            MXS_NOTICE("Query classifier initialized.");
            inited = true;
        }
    }

    return inited;
}

void qc_end(void)
{
    mysql_library_end();
}

bool qc_thread_init(void)
{
    bool inited = (mysql_thread_init() == 0);

    if (!inited)
    {
        MXS_ERROR("mysql_thread_init() failed.");
    }

    return inited;
}

void qc_thread_end(void)
{
    mysql_thread_end();
}

/**
 * EXPORTS
 */

extern "C"
{

static char version_string[] = "V1.0.0";

static QUERY_CLASSIFIER qc =
{
    qc_init,
    qc_end,
    qc_thread_init,
    qc_thread_end,
    qc_parse,
    qc_get_type,
    qc_get_operation,
    qc_get_created_table_name,
    qc_is_drop_table_query,
    qc_is_real_query,
    qc_get_table_names,
    NULL,
    qc_query_has_clause,
    qc_get_affected_fields,
    qc_get_database_names,
};

 /* @see function load_module in load_utils.c for explanation of the following
  * lint directives.
 */
/*lint -e14 */
MODULE_INFO info =
{
    MODULE_API_QUERY_CLASSIFIER,
    MODULE_IN_DEVELOPMENT,
    QUERY_CLASSIFIER_VERSION,
    const_cast<char*>("Query classifier based upon MySQL Embedded"),
};

char* version()
{
    return const_cast<char*>(version_string);
}

void ModuleInit()
{
}

QUERY_CLASSIFIER* GetModuleObject()
{
    return &qc;
}
/*lint +e14 */

}