Qore Programming Language Reference Manual: Qore::SQL::DatasourcePool Class Reference (original) (raw)

Provides transparent per-thread, per-transaction datasource connection pooling. More...

#include <[QC_DatasourcePool.dox.h](%5Fq%5Fc%5F%5F%5Fdatasource%5Fpool%5F8dox%5F8h%5Fsource.html)>

Public Member Methods
nothing	beginTransaction ()
	Manually allocates a persistent connection from the pool to the calling thread. More...
nothing	clearEventQueue ()
	Clears the queue object for DBI events on the pool. More...
	clearWarningCallback ()
	clears any connection delay warning callback from the object More...
nothing	commit ()
	Commits the current transaction and releases the connection to the pool. More...
	constructor (string driver, *string user, *string pass, *string db, *string encoding, *string host, softint min=3, softint max=10, softint port=0, *Qore::Thread::Queue queue, auto arg)
	Creates the DatasourcePool object; attempts to load a DBI driver if the driver is not already present in Qore. More...
	constructor (string desc, *Qore::Thread::Queue queue, auto arg)
	Creates a DatasourcePool object from a single string giving all parameters that can be parsed by parse_datasource() More...
	constructor (hash< auto > opts, *Qore::Thread::Queue queue, auto arg)
	Creates a DatasourcePool object from a hash argument giving parameters for the constructor. More...
	copy ()
	Creates a new Datasource object with the same driver as the original and copies of all the connection parameters. More...
bool	currentThreadInTransaction ()
	Returns True if the current thread is in a transaction (i.e. has a dedicated datasource allocation), False if not. More...
	destructor ()
	Throws an exception if any transactions are in progress and returns immediately; the object is destroyed after any in-progress requests are completed. More...
auto	exec (string sql,...)
	Allocates a persistent connection to the current thread from the pool (if one has not already been allocated) and executes an SQL command on the server and returns either the integer row count (for example, for updates, inserts, and deletes) or the data retrieved (for example, if a stored procedure is executed that returns values) More...
auto	execRaw (string sql)
	Allocates a persistent connection to the current thread from the pool (if one has not already been allocated) and executes an SQL command on the server and returns either the row count (for example, for updates and inserts) or the data retrieved (for example, if a stored procedure is executed that returns values) More...
int	getCapabilities ()
	Returns an integer bitfield of DBI driver capabilities. More...
list< auto >	getCapabilityList ()
	Returns a list of strings giving the capabilities of the current DBI driver. More...
auto	getClientVersion ()
	Retrieves the driver-specific client library version information; this method may not be implemented for all drivers. More...
hash< auto >	getConfigHash ()
	Returns a datasource hash describing the configuration of the current object. More...
string	getConfigString ()
	Returns a string giving the configuration of the current object in a format that can be parsed by parse_datasource() More...
*string	getDBCharset ()
	Retrieves the database-specific charset set encoding for the object. More...
*string	getDBEncoding ()
	Retrieves the database-specific charset set encoding for the object. More...
*string	getDBName ()
	Returns the database name parameter as a string or NOTHING if none is set. More...
string	getDriverName ()
	Returns the name of the driver used for the object. More...
string	getDriverRealName ()
	Returns the real DB driver name if supported by the driver, otherwise the Qore driver name. More...
int	getErrorTimeout ()
	Returns the error timeout period for waiting for a connection to come free as an integer giving milliseconds; note that timeout values less than or equal to zero mean that requests for a connection will wait indefinitely. More...
*string	getHostName ()
	Returns the hostname parameter as a string or NOTHING if none is set. More...
int	getMaximum ()
	Returns the maximum number of connections in this object. More...
int	getMinimum ()
	Returns the minimum number of connections in this object. More...
string	getOSCharset ()
	Returns the Qore character encoding name for the object as a string or "(unknown)" if none is set. More...
*string	getOSEncoding ()
	Returns the Qore character encoding name for the object as a string or NOTHING if none is set. More...
auto	getOption (string opt)
	Returns the current value for the given option. More...
hash< auto >	getOptionHash ()
	returns the valid options for the driver associated with the Datasource with descriptions and current values for the current Datasource object More...
*string	getPassword ()
	Returns the password parameter as a string or NOTHING if none is set. More...
*int	getPort ()
	Gets the port number that will be used for the next connection to the server. More...
AbstractSQLStatement	getSQLStatement ()
	Returns an AbstractSQLStatement object based on the current database connection object. More...
auto	getServerVersion ()
	Returns the driver-specific server version data for the current connection. More...
*hash< auto >	getUsageInfo ()
	Returns a hash with usage information about the DatasourcePool object. More...
*string	getUserName ()
	Returns the username parameter as a string or NOTHING if none is set. More...
bool	inTransaction ()
	Returns True if a transaction is currently in progress (meaning in this case that a datasource form the pool is dedicated to the calling thread), False if not. More...
nothing	rollback ()
	Rolls back the current transaction and releases the connection to the pool. More...
auto	select (string sql,...)
	Executes an SQL select statement on the server and returns the result as a hash (column names) of lists (column values per row) More...
auto	selectRow (string sql,...)
	Executes an SQL select statement on the server and returns the first row as a hash (the column values) More...
auto	selectRows (string sql,...)
	Executes an SQL select statement on the server and returns the result as a list (rows) of hashes (the column values) More...
	setErrorTimeout (timeout ts)
	Sets the timeout period for waiting for a connection to come free; note that timeout values less than or equal to zero mean that requests for a connection will wait indefinitely. More...
nothing	setEventQueue (Qore::Thread::Queue queue, auto arg)
	Sets a queue object for DBI events on the pool. More...
	setWarningCallback (timeout ms, code callback, auto arg)
	sets a connection delay warning callback to be called any time the delay assigning a connection from the pool exceeds the given timeout in milliseconds More...
string	toString ()
	Returns a string with technical information about the object. More...
auto	vexec (string sql, *softlist< auto > vargs)
	Allocates a persistent connection to the current thread from the pool (if one has not already been allocated) and executes SQL code on the DB connection, taking a list for all bind arguments. More...
auto	vselect (string sql, *softlist< auto > vargs)
	Executes a select statement on the server and returns the results in a hash (column names) of lists (column values per row), taking a list for all bind arguments. More...
auto	vselectRow (string sql, *softlist< auto > vargs)
	Executes a select statement on the server and returns the first row as a hash (column names and values), taking a list for all bind arguments. More...
auto	vselectRows (string sql, *softlist< auto > vargs)
	Executes a select statement on the server and returns the results in a list (rows) of hashes (column names and values), taking a list for all bind arguments. More...
Public Member Methods inherited from Qore::SQL::AbstractDatasource
abstract nothing	beginTransaction ()
	Manually signals the start of transaction management on the AbstractDatasource. More...
abstract nothing	commit ()
	Commits the current transaction and releases any thread resources associated with the transaction. More...
bool	currentThreadInTransaction ()
	Should return True if the current thread is in a transaction with this object, must be re-implemented in subclasses to provide the desired functionality. More...
abstract auto	exec (string sql,...)
	Executes an SQL command on the server and returns either the integer row count (for example, for updates, inserts, and deletes) or the data retrieved (for example, if a stored procedure is executed that returns values) More...
abstract auto	execRaw (string sql)
	Executes an SQL command on the server and returns either the row count (for example, for updates and inserts) or the data retrieved (for example, if a stored procedure is executed that returns values) More...
abstract auto	getClientVersion ()
	Retrieves the driver-specific client library version information. More...
abstract hash< auto >	getConfigHash ()
	Returns a datasource hash describing the configuration of the current object. More...
abstract string	getConfigString ()
	Returns a string giving the configuration of the current object in a format that can be parsed by parse_datasource() More...
abstract *string	getDBEncoding ()
	Retrieves the database-specific charset set encoding for the object. More...
abstract *string	getDBName ()
	Returns the database name parameter as a string or NOTHING if none is set. More...
abstract string	getDriverName ()
	Returns the name of the driver used for the object. More...
string	getDriverRealName ()
	Returns the real DB driver name if supported by the driver, otherwise the Qore driver name. More...
abstract *string	getHostName ()
	Returns the hostname parameter as a string or NOTHING if none is set. More...
abstract *string	getOSEncoding ()
	Returns the Qore character encoding name for the object as a string or NOTHING if none is set. More...
auto	getOption (string opt)
	Returns the current value for the given option. More...
hash< auto >	getOptionHash ()
	Returns the valid options for the driver associated with the AbstractDatasource with descriptions and current values for the current AbstractDatasource object. More...
abstract *string	getPassword ()
	Returns the password parameter as a string or NOTHING if none is set. More...
abstract *int	getPort ()
	Gets the port number that will be used for the next connection to the server. More...
AbstractSQLStatement	getSQLStatement ()
	Returns an AbstractSQLStatement object based on the current database connection object. More...
abstract auto	getServerVersion ()
	Returns the driver-specific server version data for the current connection. More...
abstract *string	getUserName ()
	Returns the username parameter as a string or NOTHING if none is set. More...
abstract bool	inTransaction ()
	Returns True if a transaction is currently in progress. More...
abstract nothing	rollback ()
	Rolls the current transaction back and releases any thread resources associated with the transaction. More...
abstract auto	select (string sql,...)
	Executes an SQL select statement on the server and (normally) returns the result as a hash (column names) of lists (column values per row) More...
abstract auto	selectRow (string sql,...)
	Executes an SQL select statement on the server and returns the first row as a hash (the column values) More...
abstract auto	selectRows (string sql,...)
	Executes an SQL select statement on the server and returns the result as a list (rows) of hashes (the column values) More...
abstract auto	vexec (string sql, *softlist< auto > vargs)
	Executes an SQL command on the server and returns either the integer row count (for example, for updates, inserts, and deletes) or the data retrieved (for example, if a stored procedure is executed that returns values), taking a list for all bind arguments. More...
abstract auto	vselect (string sql, *softlist< auto > vargs)
	Executes a select statement on the server and returns the results in a hash (column names) of lists (column values per row), taking a list for all bind arguments. More...
abstract auto	vselectRow (string sql, *softlist< auto > vargs)
	Executes a select statement on the server and returns the first row as a hash (column names and values), taking a list for all bind arguments. More...
abstract auto	vselectRows (string sql, *softlist< auto > vargs)
	Executes a select statement on the server and returns the results in a list (rows) of hashes (column names and values), taking a list for all bind arguments. More...
Public Member Methods inherited from Qore::Serializable
	constructor ()
	The constructor does not perform any action; this class is just used to mark a class as serializable by inheriting this class.
	copy ()
	The copy constructor does not perform any action; this class is just used to mark a class as serializable by inheriting this class.
	serialize (OutputStream stream)
	converts the object to binary data representing the object More...
binary	serialize ()
	converts the object to binary data representing the object More...
hash< SerializationInfo >	serializeToData ()
	converts the object to a serialization hash representing the object More...

Additional Inherited Members
Static Public Member Methods inherited from Qore::Serializable
static auto	deserialize (InputStream stream)
	Deserializes data produced with serialize() and returns the value represented by the data. More...
static auto	deserialize (binary bin)
	Deserializes data produced with serialize() and returns the value represented by the data. More...
static auto	deserialize (string bin)
	Deserializes data produced with serialize() and returns the value represented by the data. More...
static auto	deserialize (hash< SerializationInfo > data)
	Deserializes data produced with serializeToData() and returns the value represented by the data. More...
static hash< SerializationInfo >	deserializeToData (InputStream stream)
	Deserializes data produced with serialize() and returns the value represented by the data. More...
static hash< SerializationInfo >	deserializeToData (binary bin)
	Deserializes data produced with serialize() and returns the value represented by the data. More...
static	serialize (auto val, OutputStream stream)
	serializes the data and writes the serialized data to the given output stream More...
static binary	serialize (auto val)
	serializes the data and returns the serialized data as a binary object More...
static hash< SerializationInfo >	serializeToData (auto val)
	converts the value to a serialization hash representing the value More...

Provides transparent per-thread, per-transaction datasource connection pooling.

Restrictions:

Qore::PO_NO_DATABASE

Overview

In most cases, the DatasourcePool class can be used as a drop-in replacement for the Datasource class with autocommit disabled; when a transaction begins, a datasource will be automatically assigned to the calling thread, and it will only be released when a commit or rollback is called on the object. If no datasource is available, the calling thread will block until a datasource comes available.

Note that the same principles apply to SQL and database driver usage as with the Datasource class, see the Datasource class documentation for more information.

The DatasourcePool class uses Qore's thread resource tracking infrastructure to raise an exception if a thread terminates while a connection is allocated to it. If Qore user code enters a transaction with a DatasourcePool object and the thread terminates without closing the transaction (via DatasourcePool::commit() or DatasourcePool::rollback()), an exception will automatically be raised, the transaction will be rolled back, and the Datasource connection will be freed to the pool.

DatasourcePool Connection Allocations

The following methods allocate a persistent connection to the calling thread:

• DatasourcePool::exec()
• DatasourcePool::vexec()
• DatasourcePool::execRaw()
• DatasourcePool::beginTransaction() The connection is released to the pool when DatasourcePool::commit() or DatasourcePool::rollback() are called (or in the case the thread terminates, in which case an exception is raised as well).

To begin a transaction with one of the select methods (for example, with "select for update"), call DatasourcePool::beginTransaction() first to manually dedicate a Datasource to the thread before calling the select method. Otherwise statements that should be in the same transaction may be executed in different connections.

Executing a DatasourcePool method while not in a transaction is realized by allocating a temporary connection to the calling thread which is re-released when the method returns. No explicit commits are executed by the class, therefore it is an error to execute transaction-relevant commands without first calling DatasourcePool::exec(), DatasourcePool::vexec(), DatasourcePool::execRaw(), or DatasourcePool::beginTransaction().

Note that the SQLStatement class also grabs allocates a persistent connection to the calling thread when executing if it is created using a DatasourcePool object in the constructor; when connections are returned to the pool, all SQLStatement objects using the allocated datasource are closed automatically; for more information see the SQLStatement class documentation.

Thread Resource Handling

The DatasourcePool class manages connection allocations as a thread resource; if the connection is not released with a call to DatasourcePool::commit() or DatasourcePool::rollback() when the thread exits (or when Qore::throw_thread_resource_exceptions() or Qore::throw_thread_resource_exceptions_to_mark() is called), the transaction is rolled back automatically and a DATASOURCE-TRANSACTION-EXCEPTION exception is raised describing the situation.

Being an builtin class, the DatasourcePool class does not inherit AbstractThreadResource explicitly as a part of the exported API, and the internal AbstractThreadResource::cleanup() method cannot be overridden or suppressed.

Data Serialization

The DatasourcePool class supports data serialization; deserialization can fail if the database is not supported on or reachable from the target machine.

When deserializing, any datasource event queue is lost; only the connection information is propagated in the deserialized copy.

Note

This class is not available with the PO_NO_DATABASE parse option

See also

SqlUtil for a high level database-independent API

◆ beginTransaction()

◆ clearEventQueue()

Clears the queue object for DBI events on the pool.

Since

Qore 0.8.9

◆ clearWarningCallback()

clears any connection delay warning callback from the object

Example:

ds.clearWarningCallback();

Since

Qore 0.8.9

◆ commit()

◆ constructor() [1/3]

Creates a DatasourcePool object from a hash argument giving parameters for the constructor.

Parameters

Example:

Datasource db(("type": DSPGSQL, "user": "username", "pass": "password", "db": "database", "charset": "utf8", "host": "localhost", "port": 5432, "options": ("min": 3, "max": 10)));

Exceptions

◆ constructor() [2/3]

Creates a DatasourcePool object from a single string giving all parameters that can be parsed by parse_datasource()

Parameters

Example:

DatasourcePool ds("pgsql:user/pass@db01(utf8)%localhost:5432");

Exceptions

Since

Qore 0.8.6

◆ constructor() [3/3]

Creates the DatasourcePool object; attempts to load a DBI driver if the driver is not already present in Qore.

Parameters

Example:

DatasourcePool db(DSPGSQL, "user", "pass", "database", "utf8", "localhost", 3, 10, 5432);

Exceptions

◆ copy()

Creates a new Datasource object with the same driver as the original and copies of all the connection parameters.

Example:

DatasourcePool new_dsp = dsp.copy();

◆ currentThreadInTransaction()

Returns True if the current thread is in a transaction (i.e. has a dedicated datasource allocation), False if not.

Returns

True if the current thread is in a transaction (i.e. has a dedicated datasource allocation), False if not

Code Flags:

CONSTANT

Example:

bool b = db.currentThreadInTransaction();

Since

Qore 0.8.7

◆ destructor()

Throws an exception if any transactions are in progress and returns immediately; the object is destroyed after any in-progress requests are completed.

Example:

Exceptions

◆ exec()

Allocates a persistent connection to the current thread from the pool (if one has not already been allocated) and executes an SQL command on the server and returns either the integer row count (for example, for updates, inserts, and deletes) or the data retrieved (for example, if a stored procedure is executed that returns values)

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

Parameters

Returns

The return value depends on the DBI driver; normally, for commands with placeholders, a hash is returned holding the values acquired from executing the SQL statement. For all other commands, normally an integer row count is returned. However, some DBI drivers also allow select statements to be executed through this interface, which would also return a hash (column names) of lists (values for each column).

Example:

int rows = db.exec("insert into table (varchar_col, timestamp_col, blob_col, numeric_col) values (%v, %v, %v, %d)", string, now(), binary, 100);

Note

see the documentation for the DBI driver being used for additional possible exceptions

Implements Qore::SQL::AbstractDatasource.

◆ execRaw()

Allocates a persistent connection to the current thread from the pool (if one has not already been allocated) and executes an SQL command on the server and returns either the row count (for example, for updates and inserts) or the data retrieved (for example, if a stored procedure is executed that returns values)

This method does not do any variable binding, so it's useful for example for DDL statements etc

Warning:

Using this method to execute pure dynamic SQL many times with different SQL strings (as opposed to using the same string and binding by value instead of dynamic SQL) can affect application performance by prohibiting the efficient usage of the DB server's statement cache. See DB server documentation for variable binding and the SQL statement cache for more information.

Parameters

Returns

The return value depends on the DBI driver; normally, for commands with placeholders, a hash is returned holding the values acquired from executing the SQL statement. For all other commands, normally an integer row count is returned. However, some DBI drivers also allow select statements to be executed through this interface, which would also return a hash (column names) of lists (values for each column).

Example:

db.execRaw("create table my_tab (id number, some_text varchar2(30))");

Note

see the documentation for the DBI driver being used for additional possible exceptions

Implements Qore::SQL::AbstractDatasource.

◆ getCapabilities()

Returns an integer bitfield of DBI driver capabilities.

Returns

an integer bitfield of DBI driver capabilities; see DBI Capability Constants for the meaning of each bit

Code Flags:

CONSTANT

Example:

int caps = pool.getCapabilities();

if (!(caps & DBI_CAP_TRANSACTION_MANAGEMENT))

throw "DATASOURCE-ERROR", sprintf("DBI driver %y does not support transaction management", db.getDriverName());

Since

Qore 0.8.12

◆ getCapabilityList()

Returns a list of strings giving the capabilities of the current DBI driver.

Returns

a list of strings giving the capabilities of the current DBI driver

Code Flags:

CONSTANT

Example:

printf("driver %y has the following capabilities:\n", db.getDriverName());

foreach string cap in (db.getCapabilityList())

printf("- %s\n", cap);

Since

Qore 0.8.12

◆ getClientVersion()

Retrieves the driver-specific client library version information; this method may not be implemented for all drivers.

Returns

the driver-specific client library version information; this method may not be implemented for all drivers; see the DBI driver documentation for the return data type and format

Example:

auto ver = db.getClientVersion();

Note

see the documentation for the DBI driver being used for possible exceptions

Implements Qore::SQL::AbstractDatasource.

◆ getConfigHash()

◆ getConfigString()

◆ getDBCharset()

Retrieves the database-specific charset set encoding for the object.

A method synonym for DatasourcePool::getDBEncoding() kept for backwards-compatibility

Returns

the database-specific charset set encoding for the object

Code Flags:

CONSTANT

Example:

*string enc = db.getDBCharset();

◆ getDBEncoding()

◆ getDBName()

◆ getDriverName()

◆ getDriverRealName()

Returns the real DB driver name if supported by the driver, otherwise the Qore driver name.

Returns

the real DB driver name if supported by the driver, otherwise the Qore driver name

Code Flags:

RET_VALUE_ONLY

Example:

string driver = db.getDriverRealName();

The return value will differ from getDriverName() in the case of "wrapper" drivers such as odbc or jdbc, where the generic Qore driver name is insufficient to identify the database server type.

In other cases, this method will return the same value as getDriverName()

See also

getDriverRName()

Since

Qore 1.14

◆ getErrorTimeout()

Returns the error timeout period for waiting for a connection to come free as an integer giving milliseconds; note that timeout values less than or equal to zero mean that requests for a connection will wait indefinitely.

Code Flags:

CONSTANT

Example:

int ms = ds.getErrorTimeout();

Returns

the error timeout period for waiting for a connection to come free as an integer giving milliseconds; note that timeout values less than or equal to zero mean that requests for a connection will wait indefinitely

Since

Qore 0.8.9

◆ getHostName()

◆ getMaximum()

Returns the maximum number of connections in this object.

Returns

the maximum number of connections in this object

Code Flags:

CONSTANT

Example:

int max = db.getMaximum();

◆ getMinimum()

Returns the minimum number of connections in this object.

Returns

the minimum number of connections in this object

Code Flags:

CONSTANT

Example:

int min = db.getMinimum();

◆ getOption()

Returns the current value for the given option.

Code Flags:

RET_VALUE_ONLY

Parameters

Exceptions

Since

Qore 0.8.6

◆ getOptionHash()

returns the valid options for the driver associated with the Datasource with descriptions and current values for the current Datasource object

Code Flags:

CONSTANT

Returns

a hash where the keys are valid option names, and the values are hashes with the following keys:

• "desc": a string description of the option
• "type": a string giving the data type restriction for the option
• "value": the current value of the option

Since

Qore 0.8.6

◆ getOSCharset()

Returns the Qore character encoding name for the object as a string or "(unknown)" if none is set.

Returns

the Qore character encoding name for the object as a string or "(unknown)" if none is set

Code Flags:

CONSTANT

Example:

string enc = db.getOSCharset();

See also

DatasourcePool::getOSEncoding()

◆ getOSEncoding()

Returns the Qore character encoding name for the object as a string or NOTHING if none is set.

Returns

the Qore character encoding name for the object as a string or NOTHING if none is set

Code Flags:

CONSTANT

Example:

*string enc = db.getOSEncoding();

Implements Qore::SQL::AbstractDatasource.

◆ getPassword()

◆ getPort()

Gets the port number that will be used for the next connection to the server.

Invalid port numbers will cause an exception to be thrown when the connection is opened

Code Flags:

CONSTANT

Example:

*int port = db.getPort();

Implements Qore::SQL::AbstractDatasource.

◆ getServerVersion()

Returns the driver-specific server version data for the current connection.

Returns

the driver-specific server version data for the current connection; see the DBI driver documentation for the return data type and format

Example:

auto ver = db.getServerVersion();

Note

see the documentation for the DBI driver being used for additional possible exceptions

Implements Qore::SQL::AbstractDatasource.

◆ getSQLStatement()

Returns an AbstractSQLStatement object based on the current database connection object.

Example:

AbstractSQLStatement stmt = ds.getSQLStatement();

Exceptions

Since

Qore 0.9.0

◆ getUsageInfo()

Returns a hash with usage information about the DatasourcePool object.

Code Flags:

CONSTANT

Example:

hash h = ds.getUsageInfo();

Returns

a hash with the following keys (note that the callback, timeout, and optionally arg keys are only set if a warning callback is set):

• callback: the closure or call reference set as the warning callback
• timeout: an integer giving the timeout threshold in milliseconds before the warning callback is executed
• arg: an optional argument passed to the warning callback
• wait_max: the maximum number of microseconds that threads have had to wait for a free connection
• stats_reqs: the total number of requests for connections / transactions on this DatasourcePool
• stats_hits: the total number of requests for connections / transactions on this DatasourcePool that did not have to wait for a connection

Note

wait_max is reported in microseconds (1 ms = 1000 us) while the warning timeout has a resolution of milliseconds

Since

Qore 0.8.9

◆ getUserName()

◆ inTransaction()

Returns True if a transaction is currently in progress (meaning in this case that a datasource form the pool is dedicated to the calling thread), False if not.

Returns

True if a transaction is currently in progress (meaning in this case that a datasource form the pool is dedicated to the calling thread), False if not

Code Flags:

CONSTANT

Example:

bool b = db.inTransaction();

Implements Qore::SQL::AbstractDatasource.

◆ rollback()

◆ select()

Executes an SQL select statement on the server and returns the result as a hash (column names) of lists (column values per row)

The return format of this method is suitable for use with context statements, for easy iteration and processing of query results. Alternatively, the HashListIterator class can be used to iterate the return value of this method.

Additionally, this format is a more efficient format than that returned by the Datasource::selectRows() method, because the column names are not repeated for each row returned. Therefore, for retrieving anything greater than small amounts of data, it is recommended to use this method instead of Datasource::selectRows().

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

This method does not retain the datasource connection for the current thread if one was not already allocated before this method is called, so to execute select statements that begin a transaction (such as "select for update"), execute DatasourcePool::beginTransaction() first to ensure that the connection is dedicated to the calling thread.

Parameters

Returns

This method returns a hash (the keys are the column names) of lists (the column data per row) when executed with an SQL select statement, however some DBI drivers allow any SQL to be executed through this method, in which case other data types can be returned (such as an integer for a row count or a hash for output parameters when executing a stored procedure). If no rows are found, a hash of column names assigned to empty lists is returned.

Example:

hash query = db.select("select * from table where varchar_column = %v and timestamp_column > %v", string, 2007-10-11T15:31:26.289);

if (query.firstValue())

printf("got results\n");

Note

• See the documentation for the DBI driver being used for additional possible exceptions
• This method returns all the data available immediately; to process query data piecewise, use the SQLStatement class

See also

• DatasourcePool::vselect()
• ::contextIterator()
• context Statements

Implements Qore::SQL::AbstractDatasource.

◆ selectRow()

Executes an SQL select statement on the server and returns the first row as a hash (the column values)

If more than one row is returned, then it is treated as an error and a DBI-SELECT-ROW-ERROR is returned (however the DBI driver should raise its own exception here to avoid retrieving more than one row from the server). For a similar method taking a list for all bind arguments, see DatasourcePool::vselectRow().

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

This method does not retain the datasource connection for the current thread if one was not already allocated before this method is called, so to execute select statements that begin a transaction (such as "select for update"), execute DatasourcePool::beginTransaction() first to ensure that the connection is dedicated to the calling thread.

Parameters

Returns

This method normally returns a hash (the keys are the column names) of row data or NOTHING if no row is found for the query when executed with an SQL select statement, however some DBI drivers allow any SQL statement to be executed through this method (not only select statements), in this case other data types can be returned

Example:

*hash h = db.selectRow("select * from example_table where id = 1");

Exceptions

Note

see the documentation for the DBI driver being used for additional possible exceptions

Implements Qore::SQL::AbstractDatasource.

◆ selectRows()

Executes an SQL select statement on the server and returns the result as a list (rows) of hashes (the column values)

The return format of this method is not as memory efficient as that returned by the DatasourcePool::select() method, therefore for larger amounts of data, it is recommended to use DatasourcePool::select().

The usual return value of this method can be iterated with the ListHashIterator class.

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

This method does not retain the datasource connection for the current thread if one was not already allocated before this method is called, so to execute select statements that begin a transaction (such as "select for update"), execute DatasourcePool::beginTransaction() first to ensure that the connection is dedicated to the calling thread.

Parameters

Returns

Normally returns a list (rows) of hash (where the keys are the column names of each row) or NOTHING if no rows are found for the query, however some DBI drivers allow any SQL statement to be executed through this method (not only select statements), in this case other data types can be returned

Example:

*list list = db.selectRows("select * from example_table");

Note

see the documentation for the DBI driver being used for additional possible exceptions

See also

DatasourcePool::select()

Implements Qore::SQL::AbstractDatasource.

◆ setErrorTimeout()

Sets the timeout period for waiting for a connection to come free; note that timeout values less than or equal to zero mean that requests for a connection will wait indefinitely.

Example:

Since

Qore 0.8.9

◆ setEventQueue()

Sets a queue object for DBI events on the pool.

Parameters

Exceptions

Since

Qore 0.8.9

◆ setWarningCallback()

sets a connection delay warning callback to be called any time the delay assigning a connection from the pool exceeds the given timeout in milliseconds

Example:

code cb = sub (string dsstr, int us, int to) {

printf("WARNING: datasource pool %y took %f ms (threshold %d ms) to assign a new connection\n", dsstr, us.toNumber() / 1000n, to);

};

ds.setWarningCallback(5s, cb);

Parameters

Note

that the warning timeout has a resolution of milliseconds, but the actual wait time is reported in microseconds (1 ms = 1000 us)

Since

Qore 0.8.9

◆ toString()

Returns a string with technical information about the object.

Returns

a string with technical information about the object

Code Flags:

CONSTANT

Example:

string str = db.toString();

◆ vexec()

Allocates a persistent connection to the current thread from the pool (if one has not already been allocated) and executes SQL code on the DB connection, taking a list for all bind arguments.

Same as DatasourcePool::exec() except takes an explicit list for bind arguments

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

Parameters

Returns

The return value depends on the DBI driver; normally, for commands with placeholders, a hash is returned holding the values acquired from executing the SQL statement. For all other commands, normally an integer row count is returned. However, some DBI drivers also allow select statements to be executed through this interface, which would also return a hash (column names) of lists (values for each column).

Example:

int rows = db.vexec("insert into example_table value (%v, %v, %v)", arg_list);

Note

see the documentation for the DBI driver being used for additional possible exceptions

Implements Qore::SQL::AbstractDatasource.

◆ vselect()

Executes a select statement on the server and returns the results in a hash (column names) of lists (column values per row), taking a list for all bind arguments.

The return format of this method is suitable for use with context statements, for easy iteration and processing of query results. Alternatively, the HashListIterator class can be used to iterate the return value of this method.

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

This method does not retain the datasource connection for the current thread if one was not already allocated before this method is called, so to execute select statements that begin a transaction (such as "select for update"), execute DatasourcePool::beginTransaction() first to ensure that the connection is dedicated to the calling thread.

Parameters

Returns

Normally returns a hash (the keys are the column names) of list (each hash key's value is a list giving the row data), however some DBI drivers allow any SQL statement to be executed through this method (not only select statements), in this case other data types can be returned. If no rows are found, a hash of column names assigned to empty lists is returned.

Example:

hash query = db.vselect("select * from example_table where id = %v and name = %v", arg_list);

if (query.firstValue())

printf("got results\n");

Note

• See the documentation for the DBI driver being used for additional possible exceptions
• This method returns all the data available immediately; to process query data piecewise, use the SQLStatement class

See also

• DatasourcePool::select()
• ::contextIterator()
• context Statements

Implements Qore::SQL::AbstractDatasource.

◆ vselectRow()

Executes a select statement on the server and returns the first row as a hash (column names and values), taking a list for all bind arguments.

This method is the same as the DatasourcePool::selectRow() method, except this method takes a single argument after the SQL command giving the list of bind value parameters

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

This method does not retain the datasource connection for the current thread if one was not already allocated before this method is called, so to execute select statements that begin a transaction (such as "select for update"), execute DatasourcePool::beginTransaction() first to ensure that the connection is dedicated to the calling thread.

Parameters

Returns

This method normally returns a hash (the keys are the column names) of row data or NOTHING if no row is found for the query when executed with an SQL select statement, however some DBI drivers allow any SQL statement to be executed through this method (not only select statements), in this case other data types can be returned

Example:

*hash h = db.vselectRow("select * from example_table where id = %v and type = %v", arg_list);

Note

see the documentation for the DBI driver being used for additional possible exceptions

See also

DatasourcePool::selectRow()

Implements Qore::SQL::AbstractDatasource.

◆ vselectRows()

Executes a select statement on the server and returns the results in a list (rows) of hashes (column names and values), taking a list for all bind arguments.

Same as the Datasource::selectRows() method, except this method takes a single argument after the SQL command giving the list of bind value parameters.

The usual return value of this method can be iterated with the ListHashIterator class.

The return format of this method is not as memory efficient as that returned by the DatasourcePool::select() method, therefore for larger amounts of data, it is recommended to use DatasourcePool::select().

This method also accepts all bind parameters (%d, %v, %s, etc) as documented in Binding by Value and Placeholder

This method does not retain the datasource connection for the current thread if one was not already allocated before this method is called, so to execute select statements that begin a transaction (such as "select for update"), execute DatasourcePool::beginTransaction() first to ensure that the connection is dedicated to the calling thread.

Parameters

Returns

Normally returns a list (rows) of hash (where the keys are the column names of each row) or NOTHING if no rows are found for the query, however some DBI drivers allow any SQL statement to be executed through this method (not only select statements), in this case other data types can be returned

Example:

*list list = db.vselectRows("select * from example_table where id = %v and type = %v", arg_list);

Note

see the documentation for the DBI driver being used for additional possible exceptions

See also

DatasourcePool::selectRows()

Implements Qore::SQL::AbstractDatasource.