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d2sqlite3.d
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d2sqlite3.d
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// Written in the D programming language
/++
This module provides a small wrapper around SQLite for the D programming language.
It wraps the C API in an idiomatic manner and handles built-in D types and
`Nullable!T` automatically.
Authors:
Nicolas Sicard (biozic) and other contributors at $(LINK https://github.com/biozic/d2sqlite3)
Copyright:
Copyright 2011-15 Nicolas Sicard.
License:
$(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
Macros:
D = <tt>$0</tt>
DK = <strong><tt>$0</tt></strong>
+/
module d2sqlite3;
import std.algorithm;
import std.array;
import std.conv;
import std.exception;
import std.range;
import std.string;
import std.traits;
import std.typecons;
import std.typetuple;
import std.variant;
import std.c.string : memcpy;
import core.memory : GC;
public import sqlite3;
/// SQLite type codes
enum SqliteType
{
INTEGER = SQLITE_INTEGER, ///
FLOAT = SQLITE_FLOAT, ///
TEXT = SQLITE3_TEXT, ///
BLOB = SQLITE_BLOB, ///
NULL = SQLITE_NULL ///
}
/++
Gets the library's version string (e.g. "3.8.7").
+/
string versionString()
{
return to!string(sqlite3_libversion());
}
/++
Gets the library's version number (e.g. 3008007).
+/
int versionNumber() nothrow
{
return sqlite3_libversion_number();
}
unittest
{
import std.string : startsWith;
assert(versionString.startsWith("3."));
assert(versionNumber >= 3008007);
}
/++
Tells whether SQLite was compiled with the thread-safe options.
See_also: ($LINK http://www.sqlite.org/c3ref/threadsafe.html).
+/
bool threadSafe() nothrow
{
return cast(bool) sqlite3_threadsafe();
}
unittest
{
auto ts = threadSafe;
}
/++
Manually initializes (or shuts down) SQLite.
SQLite initializes itself automatically on the first request execution, so this
usually wouldn't be called. Use for instance before a call to config().
+/
void initialize()
{
auto result = sqlite3_initialize();
enforce(result == SQLITE_OK, new SqliteException("Initialization: error %s".format(result)));
}
/// Ditto
void shutdown()
{
auto result = sqlite3_shutdown();
enforce(result == SQLITE_OK, new SqliteException("Shutdown: error %s".format(result)));
}
/++
Sets a configuration option. Use before initialization, e.g. before the first
call to initialize and before execution of the first statement.
See_Also: $(LINK http://www.sqlite.org/c3ref/config.html).
+/
void config(Args...)(int code, Args args)
{
auto result = sqlite3_config(code, args);
enforce(result == SQLITE_OK,
new SqliteException("Configuration: error %s".format(result)));
}
version (D_Ddoc)
{
///
unittest
{
config(SQLITE_CONFIG_MULTITHREAD);
// Setup a logger callback function
config(SQLITE_CONFIG_LOG,
function(void* p, int code, const(char*) msg)
{
import std.stdio;
writefln("%05d | %s", code, msg.to!string);
},
null);
initialize();
}
}
else
{
unittest
{
shutdown();
config(SQLITE_CONFIG_MULTITHREAD);
config(SQLITE_CONFIG_LOG, function(void* p, int code, const(char*) msg) {}, null);
initialize();
}
}
/++
A caracteristic of user-defined functions or aggregates.
+/
enum Deterministic
{
/++
The returned value is the same if the function is called with the same parameters.
+/
yes = 0x800,
/++
The returned value can vary even if the function is called with the same parameters.
+/
no = 0
}
/++
An SQLite database connection.
This struct is a reference-counted wrapper around a $(D sqlite3*) pointer.
+/
struct Database
{
private:
struct _Payload
{
sqlite3* handle;
void* progressHandler;
this(sqlite3* handle) @safe pure nothrow
{
this.handle = handle;
}
~this()
{
if (handle)
{
auto result = sqlite3_close(handle);
enforce(result == SQLITE_OK, new SqliteException(errmsg(handle), result));
}
handle = null;
ptrFree(progressHandler);
}
@disable this(this);
void opAssign(_Payload) { assert(false); }
}
alias Payload = RefCounted!(_Payload, RefCountedAutoInitialize.no);
Payload p;
void check(int result) {
enforce(result == SQLITE_OK, new SqliteException(errmsg(p.handle), result));
}
public:
/++
Opens a database connection.
Params:
path = The path to the database file. In recent versions of SQLite, the path can be
an URI with options.
flags = Options flags.
See_Also: $(LINK http://www.sqlite.org/c3ref/open.html) to know how to use the flags
parameter or to use path as a file URI if the current configuration allows it.
+/
this(string path, int flags = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE)
{
sqlite3* hdl;
auto result = sqlite3_open_v2(path.toStringz, &hdl, flags, null);
enforce(result == SQLITE_OK, new SqliteException(p.handle
? errmsg(p.handle) : "Error opening the database", result));
p = Payload(hdl);
}
/++
Gets the SQLite internal _handle of the database connection.
+/
sqlite3* handle() @property @safe pure nothrow
{
return p.handle;
}
/++
Gets the path associated with an attached database.
Params:
database = The name of an attached database.
Returns: The absolute path of the attached database.
If there is no attached database, or if database is a temporary or
in-memory database, then null is returned.
+/
string attachedFilePath(string database = "main")
{
return sqlite3_db_filename(p.handle, database.toStringz).to!string;
}
/++
Gets the read-only status of an attached database.
Params:
database = The name of an attached database.
+/
bool isReadOnly(string database = "main")
{
int ret = sqlite3_db_readonly(p.handle, database.toStringz);
enforce(ret >= 0, new SqliteException("Database not found: %s".format(database)));
return ret == 1;
}
/++
Gets metadata for a specific table column of an attached database.
Params:
table = The name of the table.
column = The name of the column.
database = The name of a database attached. If null, then all attached databases
are searched for the table using the same algorithm used by the database engine
to resolve unqualified table references.
+/
ColumnMetadata tableColumnMetadata(string table, string column, string database = "main")
{
ColumnMetadata data;
char* pzDataType, pzCollSeq;
int notNull, primaryKey, autoIncrement;
check(sqlite3_table_column_metadata(p.handle, database.toStringz, table.toStringz,
column.toStringz, &pzDataType, &pzCollSeq, ¬Null, &primaryKey, &autoIncrement));
data.declaredTypeName = pzDataType.to!string;
data.collationSequenceName = pzCollSeq.to!string;
data.isNotNull = cast(bool) notNull;
data.isPrimaryKey = cast(bool) primaryKey;
data.isAutoIncrement = cast(bool) autoIncrement;
return data;
}
unittest
{
auto db = Database(":memory:");
db.run("CREATE TABLE test (id INTEGER PRIMARY KEY AUTOINCREMENT,
val FLOAT NOT NULL)");
assert(db.tableColumnMetadata("test", "id") ==
ColumnMetadata("INTEGER", "BINARY", false, true, true));
assert(db.tableColumnMetadata("test", "val") ==
ColumnMetadata("FLOAT", "BINARY", true, false, false));
}
/++
Explicitly closes the database.
After this function has been called successfully, using the database or one of its
prepared statement is an error.
+/
void close()
{
check(sqlite3_close(handle));
p.handle = null;
}
/++
Executes a single SQL statement and returns the results directly. It's the equivalent
of $(D prepare(sql).execute()).
The results become undefined when the Database goes out of scope and is destroyed.
+/
ResultRange execute(string sql)
{
return prepare(sql).execute();
}
///
unittest
{
auto db = Database(":memory:");
db.execute("VACUUM");
}
/++
Runs an SQL script that can contain multiple statements.
Params:
sql = The code of the script.
dg = A delegate to call for each statement to handle the results. The passed
ResultRange will be empty if a statement doesn't return rows. If the delegate
return false, the execution is aborted.
+/
void run(string sql, scope bool delegate(ResultRange) dg = null)
{
foreach (statement; sql.byStatement)
{
auto stmt = prepare(statement);
auto results = stmt.execute();
if (dg && !dg(results))
return;
}
}
///
unittest
{
auto db = Database(":memory:");
db.run(`CREATE TABLE test1 (val INTEGER);
CREATE TABLE test2 (val FLOAT);
DROP TABLE test1;
DROP TABLE test2;`);
}
/++
Prepares (compiles) a single SQL statement and returngs it, so that it can be bound to
values before execution.
The statement becomes invalid if the Database goes out of scope and is destroyed.
+/
Statement prepare(string sql)
{
return Statement(this, sql);
}
/// Convenience functions equivalent to an SQL statement.
void begin() { execute("BEGIN"); }
/// Ditto
void commit() { execute("COMMIT"); }
/// Ditto
void rollback() { execute("ROLLBACK"); }
/++
Returns the rowid of the last INSERT statement.
+/
long lastInsertRowid()
{
return sqlite3_last_insert_rowid(p.handle);
}
/++
Gets the number of database rows that were changed, inserted or deleted by the most
recently executed SQL statement.
+/
int changes() @property nothrow
{
assert(p.handle);
return sqlite3_changes(p.handle);
}
/++
Gets the number of database rows that were changed, inserted or deleted since the
database was opened.
+/
int totalChanges() @property nothrow
{
assert(p.handle);
return sqlite3_total_changes(p.handle);
}
/++
Gets the SQLite error code of the last operation.
+/
int errorCode() @property nothrow
{
return p.handle ? sqlite3_errcode(p.handle) : 0;
}
/++
Enables or disables loading extensions.
+/
void enableLoadExtensions(bool enable = true)
{
enforce(sqlite3_enable_load_extension(p.handle, enable) == SQLITE_OK,
new SqliteException("Could not enable loading extensions."));
}
/++
Loads an extension.
Params:
path = The path of the extension file.
entryPoint = The name of the entry point function. If null is passed, SQLite
uses the name of the extension file as the entry point.
+/
void loadExtension(string path, string entryPoint = null)
{
auto ret = sqlite3_load_extension(p.handle, path.toStringz, entryPoint.toStringz, null);
enforce(ret == SQLITE_OK,new SqliteException(
"Could load extension: %s:%s".format(entryPoint, path)));
}
/++
Creates and registers a new function in the database.
If a function with the same name and the same arguments already exists, it is replaced
by the new one.
The memory associated with the function will be released when the database connection
is closed.
Params:
name = The name that the function will have in the database; this name defaults to
the identifier of $(D_PARAM fun).
fun = a $(D delegate) or $(D function) that implements the function. $(D_PARAM fun)
must satisfy these criteria:
$(UL
$(LI It must not be a variadic.)
$(LI Its arguments must all have a type that is compatible with SQLite types:
it must be a boolean or numeric type, a string, an array, null,
or a Nullable!T where T is any of the previous types.)
$(LI Its return value must also be of a compatible type.)
)
det = Tells SQLite whether the result of the function is deterministic, i.e. if the
result is the same when called with the same parameters. Recent versions of SQLite
perform optimizations based on this. Set to $(D Deterministic.no) otherwise.
See_Also: $(LINK http://www.sqlite.org/c3ref/create_function.html).
+/
void createFunction(string name, T)(T fun, Deterministic det = Deterministic.yes)
{
static assert(isCallable!fun, "expecting a callable");
static assert(variadicFunctionStyle!(fun) == Variadic.no,
"variadic functions are not supported");
alias ReturnType!fun RT;
static assert(!is(RT == void), "function must not return void");
alias PT = staticMap!(Unqual, ParameterTypeTuple!fun);
extern(C) static
void x_func(sqlite3_context* context, int argc, sqlite3_value** argv)
{
PT args;
foreach (i, type; PT)
args[i] = getValue!type(argv[i]);
auto ptr = sqlite3_user_data(context);
try
setResult(context, delegateUnwrap!T(ptr)(args));
catch (Exception e)
{
auto txt = "error in function %s(): %s".format(name, e.msg);
sqlite3_result_error(context, txt.toStringz, -1);
}
}
assert(p.handle);
check(sqlite3_create_function_v2(p.handle, name.toStringz, PT.length, SQLITE_UTF8 | det,
delegateWrap(fun), &x_func, null, null, &ptrFree));
}
///
unittest
{
string fmt = "Hello, %s!";
string my_msg(string name)
{
return fmt.format(name);
}
auto db = Database(":memory:");
db.createFunction!"msg"(&my_msg);
auto msg = db.execute("SELECT msg('John')").oneValue!string;
assert(msg == "Hello, John!");
}
/++
Creates and registers a new aggregate function in the database.
Params:
T = The $(D struct) type implementing the aggregate. T must be default-construtible
(a POD type) and implement at least these two methods: $(D accumulate) and $(D result).
Each parameter and the returned type of $(D accumulate) and $(D result) must be
a boolean or numeric type, a string, an array, null, or a Nullable!T
where T is any of the previous types.
name = The name that the aggregate function will have in the database.
det = Tells SQLite whether the result of the function is deterministic, i.e. if the
result is the same when called with the same parameters. Recent versions of SQLite
perform optimizations based on this. Set to $(D Deterministic.no) otherwise.
See_Also: $(LINK http://www.sqlite.org/c3ref/create_function.html).
+/
void createAggregate(T, string name)(Deterministic det = Deterministic.yes)
{
static assert(isAggregateType!T,
name ~ " should be an aggregate type");
static assert(__traits(isPOD, T),
name ~ " should be a POD type");
static assert(is(typeof(T.accumulate) == function),
name ~ " shoud have a method named accumulate");
static assert(is(typeof(T.result) == function),
name ~ " shoud have a method named result");
static assert(variadicFunctionStyle!(T.accumulate) == Variadic.no,
"variadic functions are not supported");
static assert(variadicFunctionStyle!(T.result) == Variadic.no,
"variadic functions are not supported");
alias staticMap!(Unqual, ParameterTypeTuple!(T.accumulate)) PT;
alias ReturnType!(T.result) RT;
extern(C) static
void x_step(sqlite3_context* context, int argc, sqlite3_value** argv)
{
auto aggregate = cast(T*) sqlite3_aggregate_context(context, T.sizeof);
if (!aggregate)
{
sqlite3_result_error_nomem(context);
return;
}
PT args;
foreach (i, type; PT)
args[i] = getValue!type(argv[i]);
try
aggregate.accumulate(args);
catch (Exception e)
{
auto txt = "error in aggregate function %s(): %s".format(name, e.msg);
sqlite3_result_error(context, txt.toStringz, -1);
}
}
extern(C) static
void x_final(sqlite3_context* context)
{
auto aggregate = cast(T*) sqlite3_aggregate_context(context, T.sizeof);
if (!aggregate)
{
sqlite3_result_error_nomem(context);
return;
}
try
setResult(context, aggregate.result());
catch (Exception e)
{
auto txt = "error in aggregate function %s(): %s".format(name, e.msg);
sqlite3_result_error(context, txt.toStringz, -1);
}
}
assert(p.handle);
check(sqlite3_create_function_v2(p.handle, name.toStringz, PT.length, SQLITE_UTF8 | det,
null, null, &x_step, &x_final, null));
}
///
unittest // Aggregate creation
{
import std.array : appender, join;
static struct Joiner
{
Appender!(string[]) app;
string separator;
void accumulate(string word, string sep)
{
separator = sep;
app.put(word);
}
string result()
{
return join(app.data, separator);
}
}
auto db = Database(":memory:");
db.execute("CREATE TABLE test (word TEXT)");
db.createAggregate!(Joiner, "strjoin");
auto statement = db.prepare("INSERT INTO test VALUES (?)");
auto list = ["My", "cat", "is", "black"];
foreach (word; list)
{
statement.bind(1, word);
statement.execute();
statement.reset();
}
auto text = db.execute("SELECT strjoin(word, '-') FROM test").oneValue!string;
assert(text == "My-cat-is-black");
}
/++
Creates and registers a collation function in the database.
Params:
fun = An alias to the D implementation of the function. The function $(D_PARAM fun)
must satisfy these criteria:
$(UL
$(LI If s1 is less than s2, $(D ret < 0).)
$(LI If s1 is equal to s2, $(D ret == 0).)
$(LI If s1 is greater than s2, $(D ret > 0).)
$(LI If s1 is equal to s2, then s2 is equal to s1.)
$(LI If s1 is equal to s2 and s2 is equal to s3, then s1 is equal to s3.)
$(LI If s1 is less than s2, then s2 is greater than s1.)
$(LI If s1 is less than s2 and s2 is less than s3, then s1 is less than s3.)
)
name = The name that the function will have in the database; this name defaults to
the identifier of $(D_PARAM fun).
See_Also: $(LINK http://www.sqlite.org/lang_aggfunc.html)
+/
void createCollation(string name, T)(T fun)
{
static assert(isCallable!fun, "expecting a callable");
static assert(variadicFunctionStyle!(fun) == Variadic.no,
"variadic functions are not supported");
alias ParameterTypeTuple!fun PT;
static assert(isSomeString!(PT[0]),
"the first argument of function " ~ name ~ " should be a string");
static assert(isSomeString!(PT[1]),
"the second argument of function " ~ name ~ " should be a string");
static assert(isImplicitlyConvertible!(ReturnType!fun, int),
"function " ~ name ~ " should return a value convertible to an int");
extern (C) static
int x_compare(void* ptr, int n1, const(void*) str1, int n2, const(void*) str2)
{
auto dg = delegateUnwrap!T(ptr);
char[] s1, s2;
s1.length = n1;
s2.length = n2;
memcpy(s1.ptr, str1, n1);
memcpy(s2.ptr, str2, n2);
return dg(cast(immutable) s1, cast(immutable) s2);
}
assert(p.handle);
check(sqlite3_create_collation_v2(p.handle, name.toStringz, SQLITE_UTF8,
delegateWrap(fun), &x_compare, &ptrFree));
}
///
unittest // Collation creation
{
static int my_collation(string s1, string s2)
{
import std.uni;
return icmp(s1, s2);
}
auto db = Database(":memory:");
db.createCollation!"my_coll"(&my_collation);
db.execute("CREATE TABLE test (word TEXT)");
auto statement = db.prepare("INSERT INTO test (word) VALUES (?)");
foreach (word; ["straße", "strasses"])
{
statement.bind(1, word);
statement.execute();
statement.reset();
}
auto word = db.execute("SELECT word FROM test ORDER BY word COLLATE my_coll")
.oneValue!string;
assert(word == "straße");
}
/++
Registers a delegate as the database's update hook. Any previously set hook is released.
See_Also: $(LINK http://www.sqlite.org/c3ref/commit_hook.html).
+/
void setUpdateHook(scope void delegate(int type, string dbName, string tableName, long rowid) hook)
{
extern(C) static
void callback(void* ptr, int type, char* dbName, char* tableName, long rowid)
{
return delegateUnwrap!(void delegate(int, string, string, long))(ptr)(
type, dbName.to!string, tableName.to!string, rowid);
}
auto ptr = delegateWrap(hook);
auto prev = sqlite3_update_hook(p.handle, &callback, ptr);
ptrFree(prev);
}
///
unittest
{
int i;
auto db = Database(":memory:");
db.setUpdateHook((int type, string dbName, string tableName, long rowid) {
assert(type == SQLITE_INSERT);
assert(dbName == "main");
assert(tableName == "test");
assert(rowid == 1);
i = 42;
});
db.execute("CREATE TABLE test (val INTEGER)");
db.execute("INSERT INTO test VALUES (100)");
assert(i == 42);
}
/++
Registers a delegate as the database's commit or rollback hook.
Any previously set hook is released.
Params:
hook = For the commit hook, a delegate that should return 0 if the operation must be
aborted or another value if it can continue.
See_Also: $(LINK http://www.sqlite.org/c3ref/commit_hook.html).
+/
void setCommitHook(int delegate() hook)
{
extern(C) static int callback(void* ptr)
{
return delegateUnwrap!(int delegate())(ptr)();
}
auto ptr = delegateWrap(hook);
auto prev = sqlite3_commit_hook(p.handle, &callback, ptr);
ptrFree(prev);
}
/// Ditto
void setRollbackHook(void delegate() hook)
{
extern(C) static void callback(void* ptr)
{
delegateUnwrap!(void delegate())(ptr)();
}
auto ptr = delegateWrap(hook);
auto prev = sqlite3_rollback_hook(p.handle, &callback, ptr);
ptrFree(prev);
}
///
unittest
{
int i;
auto db = Database(":memory:");
db.setCommitHook({ i = 42; return SQLITE_OK; });
db.setRollbackHook({ i = 666; });
db.begin();
db.execute("CREATE TABLE test (val INTEGER)");
db.rollback();
assert(i == 666);
db.begin();
db.execute("CREATE TABLE test (val INTEGER)");
db.commit();
assert(i == 42);
}
/++
Sets the progress handler.
Any previously set handler is released.
Params:
pace = The approximate number of virtual machine instructions that are
evaluated between successive invocations of the handler.
handler = A delegate that should return 0 if the operation must be
aborted or another value if it can continue.
See_Also: $(LINK http://www.sqlite.org/c3ref/commit_hook.html).
+/
void setProgressHandler(int pace, int delegate() handler)
{
extern(C) static int callback(void* ptr)
{
return delegateUnwrap!(int delegate())(ptr)();
}
ptrFree(p.progressHandler);
auto ptr = delegateWrap(handler);
sqlite3_progress_handler(p.handle, pace, &callback, ptr);
p.progressHandler = ptr;
}
}
///
unittest // Documentation example
{
// Note: exception handling is left aside for clarity.
import std.typecons : Nullable;
// Open a database in memory.
auto db = Database(":memory:");
// Create a table
db.execute(
"CREATE TABLE person (
id INTEGER PRIMARY KEY,
name TEXT NOT NULL,
score FLOAT
)"
);
// Populate the table
// Prepare an INSERT statement
auto statement = db.prepare(
"INSERT INTO person (name, score)
VALUES (:name, :score)"
);
// Bind values one by one (by parameter name or index)
statement.bind(":name", "John");
statement.bind(2, 77.5);
statement.execute();
statement.reset(); // Need to reset the statement after execution.
// Bind muliple values at once
statement.bindAll("John", null);
statement.execute();
// Count the changes
assert(db.totalChanges == 2);
// Count the Johns in the table.
auto count = db.execute("SELECT count(*) FROM person WHERE name == 'John'")
.oneValue!long;
assert(count == 2);
// Read the data from the table lazily
auto results = db.execute("SELECT * FROM person");
foreach (row; results)
{
// Retrieve "id", which is the column at index 0, and contains an int,
// e.g. using the peek function (best performance).
auto id = row.peek!long(0);
// Retrieve "name", e.g. using opIndex(string), which returns a ColumnData.
auto name = row["name"].as!string;
// Retrieve "score", which is at index 3, e.g. using the peek function,
// using a Nullable type
auto score = row.peek!(Nullable!double)(3);
if (!score.isNull) {
// ...
}
}
// Read all the table in memory at once
auto data = RowCache(db.execute("SELECT * FROM person"));
foreach (row; data)
{
auto id = row[0].as!long;
auto last = row["name"].as!string;
auto score = row[2].as!(Nullable!double);
// etc.
}
}
unittest // Database construction
{
Database db1;
auto db2 = db1;
db1 = Database(":memory:");
db2 = Database("");
auto db3 = Database(null);
db1 = db2;
assert(db2.p.refCountedStore.refCount == 2);
assert(db1.p.refCountedStore.refCount == 2);
}
unittest
{
auto db = Database(":memory:");
assert(db.attachedFilePath("main") is null);
assert(!db.isReadOnly);
db.close();
}
unittest // Execute an SQL statement
{
auto db = Database(":memory:");
db.run("");
db.run("-- This is a comment!");
db.run(";");
db.run("ANALYZE; VACUUM;");
}
version (DigitalMars) unittest // Unexpected multiple statements
{
auto db = Database(":memory:");
db.execute("BEGIN; CREATE TABLE test (val INTEGER); ROLLBACK;");
assertThrown(db.execute("DROP TABLE test"));
db.execute("CREATE TABLE test (val INTEGER); DROP TABLE test;");
assertNotThrown(db.execute("DROP TABLE test"));
db.execute("SELECT 1; CREATE TABLE test (val INTEGER); DROP TABLE test;");
assertThrown(db.execute("DROP TABLE test"));
}
unittest // Multiple statements with callback
{
auto db = Database(":memory:");
RowCache[] rows;
db.run("SELECT 1, 2, 3; SELECT 'A', 'B', 'C';", (ResultRange r) {
rows ~= RowCache(r);
return true;
});
assert(equal!"a.as!int == b"(rows[0][0], [1, 2, 3]));
assert(equal!"a.as!string == b"(rows[1][0], ["A", "B", "C"]));
}
unittest // Different arguments and result types with createFunction
{
import std.math;
auto db = Database(":memory:");
T display(T)(T value)
{
return value;
}
db.createFunction!"display_integer"(&display!int);
db.createFunction!"display_float"(&display!double);
db.createFunction!"display_text"(&display!string);
db.createFunction!"display_blob"(&display!(ubyte[]));
assert(db.execute("SELECT display_integer(42)").oneValue!int == 42);
assert(db.execute("SELECT display_float(3.14)").oneValue!double == 3.14);
assert(db.execute("SELECT display_text('ABC')").oneValue!string == "ABC");
assert(db.execute("SELECT display_blob(x'ABCD')").oneValue!(ubyte[]) == cast(ubyte[]) x"ABCD");
assert(db.execute("SELECT display_integer(NULL)").oneValue!int == 0);
assert(db.execute("SELECT display_float(NULL)").oneValue!double.isNaN);
assert(db.execute("SELECT display_text(NULL)").oneValue!string is null);
assert(db.execute("SELECT display_blob(NULL)").oneValue!(ubyte[]) is null);
}
unittest // Different Nullable argument types with createFunction
{
import std.math;
auto db = Database(":memory:");
auto display(T : Nullable!U, U...)(T value)
{
if (value.isNull)
return T();
return value;
}
db.createFunction!"display_integer"(&display!(Nullable!int));
db.createFunction!"display_float"(&display!(Nullable!double));
db.createFunction!"display_text"(&display!(Nullable!string));
db.createFunction!"display_blob"(&display!(Nullable!(ubyte[])));
assert(db.execute("SELECT display_integer(42)").oneValue!(Nullable!int) == 42);
assert(db.execute("SELECT display_float(3.14)").oneValue!(Nullable!double) == 3.14);
assert(db.execute("SELECT display_text('ABC')").oneValue!(Nullable!string) == "ABC");
assert(db.execute("SELECT display_blob(x'ABCD')").oneValue!(Nullable!(ubyte[])) == cast(ubyte[]) x"ABCD");