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MXS-976: qc_sqlite: Force initialization of sqlite3 
Sqlite3 performs some lazy initialization, during which it internally
parses some SQL statements of its own. Earlier there was detection code
for noticing that, but it was costly and errorprone.

Now, sqlite3 is forced to perform the initialization at startup so that
we no longer need any detection code.
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@jhnwkmn
jhnwkmn committed Nov 18, 2016
1 parent d640291 commit ecb6680
Showing 1 changed file with 38 additions and 83 deletions.
121 changes: 38 additions & 83 deletions query_classifier/qc_sqlite/qc_sqlite.c
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Expand Up @@ -77,6 +77,7 @@ typedef struct qc_sqlite_info
size_t database_names_capacity; // The capacity of database_names.
int keyword_1; // The first encountered keyword.
int keyword_2; // The second encountered keyword.
bool initializing; // Whether we are initializing sqlite3.
} QC_SQLITE_INFO;

typedef enum qc_log_level
Expand Down Expand Up @@ -188,7 +189,6 @@ static QC_SQLITE_INFO* info_alloc(void);
static void info_finish(QC_SQLITE_INFO* info);
static void info_free(QC_SQLITE_INFO* info);
static QC_SQLITE_INFO* info_init(QC_SQLITE_INFO* info);
static bool is_submitted_query(const QC_SQLITE_INFO* info, const Parse* pParse);
static void log_invalid_data(GWBUF* query, const char* message);
static bool parse_query(GWBUF* query);
static void parse_query_string(const char* query, size_t len);
Expand Down Expand Up @@ -381,6 +381,7 @@ static QC_SQLITE_INFO* info_init(QC_SQLITE_INFO* info)
info->database_names_capacity = 0;
info->keyword_1 = 0; // Sqlite3 starts numbering tokens from 1, so 0 means
info->keyword_2 = 0; // that we have not seen a keyword.
info->initializing = false;

return info;
}
Expand Down Expand Up @@ -528,76 +529,6 @@ static bool query_is_parsed(GWBUF* query)
return query && GWBUF_IS_PARSED(query);
}

/*
* Check that the statement being reported about is the one that initially was
* submitted to parse_query_string(...). When sqlite3 is parsing other statements
* it may (right after it's used for the first time) parse selects of its own.
* We need to detect that, so that the internal stuff is not allowed to interfere
* with the parsing of the provided statement.
*
* @param info The thread specific info structure.
* @param pParse Sqlite3's parse context.
*
* @return True, if the current callback relates to the provided query,
* false otherwise.
*/
static bool is_submitted_query(const QC_SQLITE_INFO* info, const Parse* pParse)
{
bool rv = false;

if (*pParse->zTail == 0)
{
// Everything has been consumed => the callback relates to the statement
// that was provided to parse_query_string(...).
rv = true;
}
else if (pParse->sLastToken.z && (*pParse->sLastToken.z == ';'))
{
// A ';' has been reached, i.e. everything has been consumed => the callback
// relates to the statement that was provided to parse_query_string(...).
rv = true;
}
else
{
// If info->query contains a trailing ';', pParse->zTail may or may not contain
// one also. We need to cater for the situation that the former has one and the
// latter does not.
const char* i = info->query;
const char* end = i + info->query_len;
const char* j = pParse->zTail;

// Walk forward as long as neither has reached the end,
// and the characters are the same.
while ((i < end) && (*j != 0) && (*i == *j))
{
++i;
++j;
}

if (i == end)
{
// If i has reached the end, then if j also has reached the end,
// both are the same. In this case both either have or have not
// a trailing ';'.
rv = (*j == 0);
}
else if (*j == 0)
{
// Else if j has reached the end, then if i points to ';', both
// are the same. In this case info->query contains a trailing ';'
// while pParse->zTail does not.
rv = (*i == ';');
}
else
{
// Otherwise they are not the same.
rv = false;
}
}

return rv;
}

/**
* Logs information about invalid data.
*
Expand Down Expand Up @@ -1271,7 +1202,7 @@ void mxs_sqlite3EndTable(Parse *pParse, /* Parse context */
QC_SQLITE_INFO* info = this_thread.info;
ss_dassert(info);

if (is_submitted_query(info, pParse))
if (!info->initializing)
{
if (pSelect)
{
Expand Down Expand Up @@ -1359,10 +1290,7 @@ int mxs_sqlite3Select(Parse* pParse, Select* p, SelectDest* pDest)
QC_SQLITE_INFO* info = this_thread.info;
ss_dassert(info);

// Check whether the statement being parsed is the one that was passed
// to sqlite3_prepare in parse_query_string(). During inserts, sqlite may
// parse selects of its own.
if (is_submitted_query(info, pParse))
if (!info->initializing)
{
info->status = QC_QUERY_PARSED;
info->operation = QUERY_OP_SELECT;
Expand Down Expand Up @@ -1391,7 +1319,7 @@ void mxs_sqlite3StartTable(Parse *pParse, /* Parser context */
QC_SQLITE_INFO* info = this_thread.info;
ss_dassert(info);

if (is_submitted_query(info, pParse))
if (!info->initializing)
{
info->status = QC_QUERY_PARSED;
info->operation = QUERY_OP_CREATE;
Expand Down Expand Up @@ -2479,14 +2407,13 @@ static bool qc_sqlite_init(const char* args)

if (sqlite3_initialize() == 0)
{
init_builtin_functions();

this_unit.initialized = true;
this_unit.log_level = log_level;

if (qc_sqlite_thread_init())
{
init_builtin_functions();

this_unit.log_level = log_level;

if (log_level != QC_LOG_NOTHING)
{
const char* message;
Expand Down Expand Up @@ -2550,10 +2477,38 @@ static bool qc_sqlite_thread_init(void)
int rc = sqlite3_open(":memory:", &this_thread.db);
if (rc == SQLITE_OK)
{
this_thread.initialized = true;

MXS_INFO("qc_sqlite: In-memory sqlite database successfully opened for thread %lu.",
(unsigned long) pthread_self());

QC_SQLITE_INFO* info = info_alloc();

if (info)
{
this_thread.info = info;

// With this statement we cause sqlite3 to initialize itself, so that it
// is not done as part of the actual classification of data.
const char* s = "CREATE TABLE __maxscale__internal__ (int field UNIQUE)";
size_t len = strlen(s);

this_thread.info->query = s;
this_thread.info->query_len = len;
this_thread.info->initializing = true;
parse_query_string(s, len);
this_thread.info->initializing = false;
this_thread.info->query = NULL;
this_thread.info->query_len = 0;

info_free(this_thread.info);
this_thread.info = NULL;

this_thread.initialized = true;
}
else
{
sqlite3_close(this_thread.db);
this_thread.db = NULL;
}
}
else
{
Expand Down

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