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Refactor Connection Reset Handling

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* Introduced startup parameters in PgSQL_Connection (removed default session parameters from PgSQL_Session)
* Startup parameters are populated during both frontend and backend connection creation
* Parameters provided via connection options are set as startup parameters
* Backend connection parameter handling updated: only critical variables are now set via connection options to prevent interference with DISCARD ALL during connection reset; remaining parameters will be applied using individual SET commands
pull/5060/head
Rahim Kanji 9 months ago
parent 431fda06b4
commit 1bcd09044b
7 changed files with 168 additions and 125 deletions
Show Stats Download Patch File Download Diff File

45
include/PgSQL_Connection.h
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@ -244,7 +244,7 @@ class PgSQL_Connection_userinfo {
class PgSQL_Connection {
public:
PgSQL_Connection();
PgSQL_Connection(bool is_client_conn);
~PgSQL_Connection();
PG_ASYNC_ST handler(short event);
@ -312,7 +312,7 @@ public:
if (error_info.severity == PGSQL_ERROR_SEVERITY::ERRSEVERITY_FATAL ||
error_info.severity == PGSQL_ERROR_SEVERITY::ERRSEVERITY_ERROR ||
error_info.severity == PGSQL_ERROR_SEVERITY::ERRSEVERITY_PANIC) {
return true;
return true;
}
return false;
}
@ -442,6 +442,42 @@ public:
bool IsKeepMultiplexEnabledVariables(char* query_digest_text);
/**
* @brief Retrieves startup parameter and it's hash
*
* This function tries to retrieve value and hash of startup paramters if present (provided in connection parameters).
* If value is not found, it falls back to the thread-specific default variables.
*
* @param idx The index of startup parameter to retrieve.
* @return The value and hash of startup parameter.
*
*/
std::pair<const char*, uint32_t> get_startup_parameter_and_hash(enum pgsql_variable_name idx);
/**
* @brief Copies tracked PgSQL session variables to startup parameters
*
* This function synchronizes the current tracked session variables (in `variables` and `var_hash`)
* to the startup parameters arrays (`startup_parameters` and `startup_parameters_hash`). If `copy_only_critical_param`
* is true, only the critical parameters (indices 0 to PGSQL_NAME_LAST_LOW_WM-1) are copied.
* Otherwise, all tracked variables up to PGSQL_NAME_LAST_HIGH_WM are copied.
*
* @param copy_only_critical_param If true, only critical parameters are copied; otherwise, all tracked variables.
*/
void copy_pgsql_variables_to_startup_parameters(bool copy_only_critical_param);
/**
* @brief Copies startup parameters to tracked PgSQL session variables.
*
* This function synchronizes the startup parameters arrays (`startup_parameters` and `startup_parameters_hash`)
* to the tracked session variables (`variables` and `var_hash`). If `copy_only_critical_param` is true,
* only the critical parameters (indices 0 to PGSQL_NAME_LAST_LOW_WM-1) are copied. Otherwise, all tracked
* variables up to PGSQL_NAME_LAST_HIGH_WM are copied.
*
* @param copy_only_critical_param If true, only critical parameters are copied; otherwise, all tracked variables.
*/
void copy_startup_parameters_to_pgsql_variables(bool copy_only_critical_param);
struct {
unsigned long length;
char* ptr;
@ -471,6 +507,9 @@ public:
bool var_absent[PGSQL_NAME_LAST_HIGH_WM] = { false };
std::vector<uint32_t> dynamic_variables_idx;
uint32_t startup_parameters_hash[PGSQL_NAME_LAST_HIGH_WM] = {};
char* startup_parameters[PGSQL_NAME_LAST_HIGH_WM] = {};
/**
* @brief Keeps tracks of the 'server_status'. Do not confuse with the 'server_status' from the
* 'MYSQL' connection itself. This flag keeps track of the configured server status from the
@ -499,7 +538,7 @@ public:
bool reusable;
bool processing_multi_statement;
bool multiplex_delayed;
bool is_client_connection; // true if this is a client connection, false if it is a server connection
PgSQL_SrvC *parent;
PgSQL_Connection_userinfo* userinfo;

17
include/PgSQL_Session.h
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@ -369,7 +369,6 @@ public:
PtrSize_t pkt;
std::string untracked_option_parameters;
PgSQL_DateStyle_t current_datestyle = {};
char* default_session_variables[PGSQL_NAME_LAST_HIGH_WM] = {};
#if 0
// uint64_t
@ -526,22 +525,6 @@ public:
void detected_broken_connection(const char* file, unsigned int line, const char* func, const char* action, PgSQL_Connection* myconn, bool verbose = false);
void generate_status_one_hostgroup(int hid, std::string& s);
void set_previous_status_mode3(bool allow_execute = true);
void set_default_session_variable(enum pgsql_variable_name idx, const char* value);
/**
* @brief Retrieves default session variable
*
* This function tries to retrieve value of default session variable if present (provided in connection parameters).
* If value is not found, it falls back to the thread-specific default variables.
*
* @param idx The index of the session variable to retrieve.
* @return The value of the session variable
*
*/
const char* get_default_session_variable(enum pgsql_variable_name idx);
void reset_default_session_variable(enum pgsql_variable_name idx);
};
#define PgSQL_KILL_QUERY 1

2
lib/Base_Thread.cpp
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@ -132,7 +132,7 @@ S Base_Thread::create_new_session_and_client_data_stream(int _fd) {
sess->client_myds->myprot.dump_pkt = true;
#endif
if constexpr (std::is_same_v<T, PgSQL_Thread>) {
PgSQL_Connection* myconn = new PgSQL_Connection();
PgSQL_Connection* myconn = new PgSQL_Connection(true);
sess->client_myds->attach_connection(myconn);
} else if constexpr (std::is_same_v<T, MySQL_Thread>) {
MySQL_Connection* myconn = new MySQL_Connection();

147
lib/PgSQL_Connection.cpp
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@ -147,8 +147,9 @@ void print_backtrace(void);
#define NEXT_IMMEDIATE(new_st) do { async_state_machine = new_st; goto handler_again; } while (0)
PgSQL_Connection::PgSQL_Connection() {
PgSQL_Connection::PgSQL_Connection(bool is_client_conn) {
proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 4, "Creating new PgSQL_Connection %p\n", this);
is_client_connection = is_client_conn;
pgsql_conn = NULL;
result_type = 0;
pgsql_result = NULL;
@ -215,13 +216,6 @@ PgSQL_Connection::~PgSQL_Connection() {
delete query_result_reuse;
query_result_reuse = NULL;
}
for (int i = 0; i < PGSQL_NAME_LAST_HIGH_WM; i++) {
if (variables[i].value) {
free(variables[i].value);
variables[i].value = NULL;
var_hash[i] = 0;
}
}
if (connected_host_details.hostname) {
free(connected_host_details.hostname);
@ -233,6 +227,21 @@ PgSQL_Connection::~PgSQL_Connection() {
}
if (options.init_connect) free(options.init_connect);
for (int i = 0; i < PGSQL_NAME_LAST_HIGH_WM; ++i) {
if (variables[i].value) {
free(variables[i].value);
variables[i].value = NULL;
var_hash[i] = 0;
}
}
for (int i = 0; i < PGSQL_NAME_LAST_HIGH_WM; ++i) {
if (startup_parameters[i]) {
free(startup_parameters[i]);
startup_parameters_hash[i] = 0;
}
}
}
void PgSQL_Connection::next_event(PG_ASYNC_ST new_st) {
@ -756,44 +765,28 @@ void PgSQL_Connection::connect_start() {
// charset validation is already done
pgsql_variables.server_set_hash_and_value(myds->sess, PGSQL_CLIENT_ENCODING, client_charset, client_charset_hash);
std::vector<unsigned int> client_options;
client_options.reserve(PGSQL_NAME_LAST_LOW_WM + myds->sess->client_myds->myconn->dynamic_variables_idx.size());
// optimized way to set client parameters on backend connection when creating a new connection
conninfo << "options='";
// excluding client_encoding, which is already set above
for (int idx = 1; idx < PGSQL_NAME_LAST_LOW_WM; idx++) {
const char* value = pgsql_variables.client_get_value(myds->sess, idx);
const char* escaped_str = escape_string_backslash_spaces(value);
conninfo << "-c " << pgsql_tracked_variables[idx].set_variable_name << "=" << escaped_str << " ";
if (escaped_str != value)
free((char*)escaped_str);
// excluding PGSQL_CLIENT_ENCODING
for (unsigned int idx = 1; idx < PGSQL_NAME_LAST_LOW_WM; idx++) {
if (pgsql_variables.client_get_hash(myds->sess, idx) == 0) continue;
client_options.push_back(idx);
const uint32_t hash = pgsql_variables.client_get_hash(myds->sess, idx);
pgsql_variables.server_set_hash_and_value(myds->sess, idx, value, hash);
}
for (uint32_t idx : myds->sess->client_myds->myconn->dynamic_variables_idx) {
assert(pgsql_variables.client_get_hash(myds->sess, idx));
client_options.push_back(idx);
}
myds->sess->mybe->server_myds->myconn->copy_pgsql_variables_to_startup_parameters(true);
if (client_options.empty() == false ||
myds->sess->untracked_option_parameters.empty() == false) {
// optimized way to set client parameters on backend connection when creating a new connection
conninfo << "options='";
for (int idx : client_options) {
const char* value = pgsql_variables.client_get_value(myds->sess, idx);
const char* escaped_str = escape_string_backslash_spaces(value);
conninfo << "-c " << pgsql_tracked_variables[idx].set_variable_name << "=" << escaped_str << " ";
if (escaped_str != value)
free((char*)escaped_str);
const uint32_t hash = pgsql_variables.client_get_hash(myds->sess, idx);
pgsql_variables.server_set_hash_and_value(myds->sess, idx, value, hash);
}
myds->sess->mybe->server_myds->myconn->reorder_dynamic_variables_idx();
// if there are untracked parameters, the session should lock on the host group
if (myds->sess->untracked_option_parameters.empty() == false) {
conninfo << myds->sess->untracked_option_parameters;
}
conninfo << "'";
// if there are untracked parameters, the session should lock on the host group
if (myds->sess->untracked_option_parameters.empty() == false) {
conninfo << myds->sess->untracked_option_parameters;
}
conninfo << "'";
}
/*conninfo << "postgres://";
@ -1881,16 +1874,19 @@ void PgSQL_Connection::reset() {
reusable = true;
creation_time = monotonic_time();
for (int i = 0; i < PGSQL_NAME_LAST_HIGH_WM; i++) {
for (int i = (is_client_connection ? 0 : PGSQL_NAME_LAST_LOW_WM + 1);
i < PGSQL_NAME_LAST_HIGH_WM;
i++) {
var_hash[i] = 0;
if (variables[i].value) {
free(variables[i].value);
variables[i].value = NULL;
var_hash[i] = 0;
}
}
dynamic_variables_idx.clear();
if (!is_client_connection) copy_startup_parameters_to_pgsql_variables(/*copy_only_critical_param=*/true);
if (options.init_connect) {
free(options.init_connect);
options.init_connect = NULL;
@ -2202,3 +2198,68 @@ void PgSQL_Connection::set_error_from_PQerrorMessage() {
const std::string_view& full_msg = !primary_msg.empty() ? primary_msg : lib_errmsg;
PgSQL_Error_Helper::fill_error_info(error_info, sqlstate.data(), full_msg.data(), severity.data());
}
std::pair<const char*, uint32_t> PgSQL_Connection::get_startup_parameter_and_hash(enum pgsql_variable_name idx) {
// within valid range?
assert(idx >= 0 && idx < PGSQL_NAME_LAST_HIGH_WM);
// Attempt to retrieve value from default startup parameters
if (startup_parameters_hash[idx] != 0) {
assert(startup_parameters[idx]);
return { startup_parameters[idx], startup_parameters_hash[idx] };
}
// fall back to thread-specific default
return { pgsql_thread___default_variables[idx], 0 };
}
void PgSQL_Connection::copy_pgsql_variables_to_startup_parameters(bool copy_only_critical_param) {
//memcpy(startup_parameters_hash, var_hash, sizeof(uint32_t) * PGSQL_NAME_LAST_LOW_WM);
for (int i = 0; i < PGSQL_NAME_LAST_LOW_WM; ++i) {
assert(var_hash[i]);
assert(variables[i].value);
startup_parameters_hash[i] = var_hash[i];
free(startup_parameters[i]);
startup_parameters[i] = strdup(variables[i].value);
}
if (copy_only_critical_param) return;
for (int i = PGSQL_NAME_LAST_LOW_WM + 1; i < PGSQL_NAME_LAST_HIGH_WM; i++) {
if (var_hash[i] != 0) {
startup_parameters_hash[i] = var_hash[i];
free(startup_parameters[i]);
startup_parameters[i] = strdup(variables[i].value);
} else {
startup_parameters_hash[i] = 0;
free(startup_parameters[i]);
startup_parameters[i] = nullptr;
}
}
}
void PgSQL_Connection::copy_startup_parameters_to_pgsql_variables(bool copy_only_critical_param) {
//memcpy(var_hash, startup_parameters_hash, sizeof(uint32_t) * PGSQL_NAME_LAST_LOW_WM);
for (int i = 0; i < PGSQL_NAME_LAST_LOW_WM; i++) {
assert(startup_parameters_hash[i]);
assert(startup_parameters[i]);
var_hash[i] = startup_parameters_hash[i];
free(variables[i].value);
variables[i].value = strdup(startup_parameters[i]);
}
if (copy_only_critical_param) return;
for (int i = PGSQL_NAME_LAST_LOW_WM + 1; i < PGSQL_NAME_LAST_HIGH_WM; i++) {
if (startup_parameters_hash[i]) {
var_hash[i] = startup_parameters_hash[i];
free(variables[i].value);
variables[i].value = strdup(startup_parameters[i]);
} else {
var_hash[i] = 0;
free(variables[i].value);
variables[i].value = nullptr;
}
}
}

6
lib/PgSQL_HostGroups_Manager.cpp
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@ -2298,7 +2298,7 @@ PgSQL_Connection * PgSQL_SrvConnList::get_random_MyConn(PgSQL_Session *sess, boo
}
// we must create a new connection
conn = new PgSQL_Connection();
conn = new PgSQL_Connection(false);
conn->parent=mysrvc;
// if attributes.multiplex == true , STATUS_MYSQL_CONNECTION_NO_MULTIPLEX_HG is set to false. And vice-versa
conn->set_status(!conn->parent->myhgc->attributes.multiplex, STATUS_MYSQL_CONNECTION_NO_MULTIPLEX_HG);
@ -2312,7 +2312,7 @@ PgSQL_Connection * PgSQL_SrvConnList::get_random_MyConn(PgSQL_Session *sess, boo
unsigned int conns_free = mysrvc->ConnectionsFree->conns_length();
unsigned int conns_used = mysrvc->ConnectionsUsed->conns_length();
if ((conns_used > conns_free) && (mysrvc->max_connections > (conns_free/2 + conns_used/2)) ) {
conn = new PgSQL_Connection();
conn = new PgSQL_Connection(false);
conn->parent=mysrvc;
// if attributes.multiplex == true , STATUS_MYSQL_CONNECTION_NO_MULTIPLEX_HG is set to false. And vice-versa
conn->set_status(!conn->parent->myhgc->attributes.multiplex, STATUS_MYSQL_CONNECTION_NO_MULTIPLEX_HG);
@ -2357,7 +2357,7 @@ PgSQL_Connection * PgSQL_SrvConnList::get_random_MyConn(PgSQL_Session *sess, boo
__sync_fetch_and_add(&PgHGM->status.server_connections_delayed, 1);
return NULL;
} else {
conn = new PgSQL_Connection();
conn = new PgSQL_Connection(false);
conn->parent=mysrvc;
// if attributes.multiplex == true , STATUS_MYSQL_CONNECTION_NO_MULTIPLEX_HG is set to false. And vice-versa
conn->set_status(!conn->parent->myhgc->attributes.multiplex, STATUS_MYSQL_CONNECTION_NO_MULTIPLEX_HG);

4
lib/PgSQL_Protocol.cpp
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@ -1211,11 +1211,9 @@ EXECUTION_STATE PgSQL_Protocol::process_handshake_response_packet(unsigned char*
if (pgsql_variables.client_set_value(sess, PGSQL_DATESTYLE, datestyle.c_str(), false)) {
// change current datestyle
sess->current_datestyle = PgSQL_DateStyle_Util::parse_datestyle(datestyle);
sess->set_default_session_variable(PGSQL_DATESTYLE, datestyle.c_str());
}
} else {
pgsql_variables.client_set_value(sess, idx, value_copy.c_str(), false);
sess->set_default_session_variable((enum pgsql_variable_name)idx, value_copy.c_str());
}
} else {
// parameter provided is not part of the tracked variables. Will lock on hostgroup on next query.
@ -1234,10 +1232,10 @@ EXECUTION_STATE PgSQL_Protocol::process_handshake_response_packet(unsigned char*
continue;
const char* val = pgsql_thread___default_variables[i];
pgsql_variables.client_set_value(sess, i, val, false);
sess->set_default_session_variable((pgsql_variable_name)i, val);
}
sess->client_myds->myconn->reorder_dynamic_variables_idx();
sess->client_myds->myconn->copy_pgsql_variables_to_startup_parameters(false);
}
else {
// we always duplicate username and password, or crashes happen

72
lib/PgSQL_Session.cpp
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@ -617,16 +617,14 @@ void PgSQL_Session::reset() {
}
}
}
if (client_myds) {
if (client_myds->myconn) {
client_myds->myconn->reset();
}
if (client_myds && client_myds->myconn) {
client_myds->myconn->reset();
}
}
PgSQL_Session::~PgSQL_Session() {
reset(); // we moved this out to allow CHANGE_USER
reset();
if (locked_on_hostgroup >= 0) {
thread->status_variables.stvar[st_var_hostgroup_locked]--;
@ -676,10 +674,6 @@ PgSQL_Session::~PgSQL_Session() {
delete proxysql_node_address;
proxysql_node_address = NULL;
}
for (int i = 0; i < PGSQL_NAME_LAST_HIGH_WM; i++) {
reset_default_session_variable((enum pgsql_variable_name)i);
}
if (transaction_state_manager)
delete transaction_state_manager;
}
@ -1161,7 +1155,7 @@ void PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
newsess->thread_session_id = __sync_fetch_and_add(&glovars.thread_id, 1);
}
newsess->status = WAITING_CLIENT_DATA;
PgSQL_Connection* myconn = new PgSQL_Connection;
PgSQL_Connection* myconn = new PgSQL_Connection(true);
newsess->client_myds->attach_connection(myconn);
newsess->client_myds->myprot.init(&newsess->client_myds, newsess->client_myds->myconn->userinfo, newsess);
newsess->mirror = true;
@ -4224,7 +4218,7 @@ bool PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
if (idx != PGSQL_NAME_LAST_HIGH_WM) {
if ((value1.size() == sizeof("DEFAULT") - 1) && strncasecmp(value1.c_str(), (char*)"DEFAULT",sizeof("DEFAULT")-1) == 0) {
value1 = get_default_session_variable((enum pgsql_variable_name)idx);
std::tie(value1, std::ignore) = client_myds->myconn->get_startup_parameter_and_hash((enum pgsql_variable_name)idx);
}
char* transformed_value = nullptr;
@ -4278,7 +4272,7 @@ bool PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
// No need to set send_param_status to true, as the original DateStyle value may have been modified.
// When send_param_status is true, it always sends the original value provided by the user in the SET statement.
if (IS_PGTRACKED_VAR_OPTION_SET_PARAM_STATUS(pgsql_tracked_variables[idx])) {
param_status.push_back(std::make_pair(var, value1));
param_status.emplace_back(var, value1);
}
} else {
send_param_status = IS_PGTRACKED_VAR_OPTION_SET_PARAM_STATUS(pgsql_tracked_variables[idx]);
@ -4461,7 +4455,7 @@ bool PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
}
if (send_param_status)
param_status.push_back(std::make_pair(var, *values));
param_status.emplace_back(var, *values);
}
if (failed_to_parse_var) {
@ -4643,16 +4637,16 @@ bool PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
for (int idx = 0; idx < PGSQL_NAME_LAST_LOW_WM; idx++) {
const char* name = pgsql_tracked_variables[idx].set_variable_name;
const char* value = get_default_session_variable((enum pgsql_variable_name)idx);
auto [value, hash] = client_myds->myconn->get_startup_parameter_and_hash((enum pgsql_variable_name)idx);
proxy_debug(PROXY_DEBUG_MYSQL_COM, 8, "Changing connection %s to %s\n", name, value);
uint32_t var_hash_int = SpookyHash::Hash32(value, strlen(value), 10);
uint32_t var_hash_int = ((hash != 0) ? hash : SpookyHash::Hash32(value, strlen(value), 10));
if (pgsql_variables.client_get_hash(this, idx) != var_hash_int) {
if (!pgsql_variables.client_set_value(this, idx, value, false)) {
return false;
}
if (IS_PGTRACKED_VAR_OPTION_SET_PARAM_STATUS(pgsql_tracked_variables[idx])) {
param_status.push_back(std::make_pair(name, value));
param_status.emplace_back(name, value);
}
}
}
@ -4660,15 +4654,15 @@ bool PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
for (int idx : client_myds->myconn->dynamic_variables_idx) {
assert(idx < PGSQL_NAME_LAST_HIGH_WM);
const char* name = pgsql_tracked_variables[idx].set_variable_name;
const char* value = get_default_session_variable((enum pgsql_variable_name)idx);
auto [value, hash] = client_myds->myconn->get_startup_parameter_and_hash((enum pgsql_variable_name)idx);
proxy_debug(PROXY_DEBUG_MYSQL_COM, 8, "Changing connection %s to %s\n", name, value);
uint32_t var_hash_int = SpookyHash::Hash32(value, strlen(value), 10);
uint32_t var_hash_int = ((hash != 0) ? hash : SpookyHash::Hash32(value, strlen(value), 10));
if (pgsql_variables.client_get_hash(this, idx) != var_hash_int) {
if (!pgsql_variables.client_set_value(this, idx, value, false)) {
return false;
}
if (IS_PGTRACKED_VAR_OPTION_SET_PARAM_STATUS(pgsql_tracked_variables[idx])) {
param_status.push_back(std::make_pair(name, value));
param_status.emplace_back(name, value);
}
}
}
@ -4696,16 +4690,16 @@ bool PgSQL_Session::handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_C
if (idx != PGSQL_NAME_LAST_HIGH_WM) {
const char* name = pgsql_tracked_variables[idx].set_variable_name;
const char* value = get_default_session_variable((enum pgsql_variable_name)idx);
uint32_t var_hash_int = SpookyHash::Hash32(value, strlen(value), 10);
auto [value, hash] = client_myds->myconn->get_startup_parameter_and_hash((enum pgsql_variable_name)idx);
uint32_t var_hash_int = ((hash != 0) ? hash : SpookyHash::Hash32(value, strlen(value), 10));
if (pgsql_variables.client_get_hash(this, idx) != var_hash_int) {
if (!pgsql_variables.client_set_value(this, idx, value, true)) {
return false;
}
if (IS_PGTRACKED_VAR_OPTION_SET_PARAM_STATUS(pgsql_tracked_variables[idx])) {
proxy_debug(PROXY_DEBUG_MYSQL_COM, 8, "Changing connection %s to %s\n", name, value);
param_status.emplace_back(std::make_pair(name, value));
param_status.emplace_back(name, value);
}
}
} else {
@ -5970,38 +5964,6 @@ void PgSQL_Session::switch_fast_forward_to_normal_mode() {
}
}
void PgSQL_Session::set_default_session_variable(enum pgsql_variable_name idx, const char* value) {
assert(value);
if (idx >= 0 && idx < PGSQL_NAME_LAST_HIGH_WM) {
if (default_session_variables[idx]) {
free(default_session_variables[idx]);
}
default_session_variables[idx] = strdup(value);
}
}
const char* PgSQL_Session::get_default_session_variable(enum pgsql_variable_name idx) {
// Check if index is within valid range
if (idx >= 0 && idx < PGSQL_NAME_LAST_HIGH_WM) {
// Attempt to retrieve value from default session variables
const char* val = default_session_variables[idx];
// Return the found value, or fall back to thread-specific default if null
return (val) ? val : pgsql_thread___default_variables[idx];
}
return NULL;
}
void PgSQL_Session::reset_default_session_variable(enum pgsql_variable_name idx) {
if (idx >= 0 && idx < PGSQL_NAME_LAST_HIGH_WM) {
if (default_session_variables[idx]) {
free(default_session_variables[idx]);
default_session_variables[idx] = NULL;
}
}
}
// Optimized single‐pass parser for PostgreSQL DateStyle strings.
// It supports input in one of these forms:
// - "ISO, MDY" (two tokens separated by a comma)

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