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/*
2022-08-16
The author disclaims copyright to this source code. In place of a
legal notice, here is a blessing:
* May you do good and not evil.
* May you find forgiveness for yourself and forgive others.
* May you share freely, never taking more than you give.
***********************************************************************
A basic demonstration of the SQLite3 OO API #1, shorn of assertions
and the like to improve readability.
*/
'use strict';
(function(){
const toss = function(...args){throw new Error(args.join(' '))};
const debug = console.debug.bind(console),
log = console.log.bind(console),
warn = console.warn.bind(console),
error = console.error.bind(console);
const demo1 = function(sqlite3){
const capi = sqlite3.capi,
oo = sqlite3.oo1,
wasm = capi.wasm;
// If we have persistent storage, maybe init and mount it:
const dbDir = true
? "" // this demo works better without persistent storage.
: capi.sqlite3_web_persistent_dir();
// ^^^ returns name of persistent mount point or "" if we have none
const db = new oo.DB(dbDir+"/mydb.sqlite3");
/**
Never(!) rely on garbage collection to clean up DBs and
(especially) statements. Always wrap their lifetimes in
try/finally construct...
*/
try {
log("Create a table...");
db.exec("CREATE TABLE IF NOT EXISTS t(a,b)");
//Equivalent:
db.exec({
sql:"CREATE TABLE IF NOT EXISTS t(a,b)"
// ... numerous other options ...
});
// SQL can be either a string or a byte array
log("Insert some data using exec()...");
let i;
for( i = 1; i <= 5; ++i ){
db.exec({
sql: "insert into t(a,b) values (?,?)",
// bind by parameter index...
bind: [i, i*2]
});
db.exec({
sql: "insert into t(a,b) values ($a,$b)",
// bind by parameter name...
bind: {$a: i * 3, $b: i * 4}
});
}
log("Insert using a prepared statement...");
let q = db.prepare("insert into t(a,b) values(?,?)");
try {
for( i = 100; i < 103; ++i ){
q.bind( [i, i*2] ).step();
q.reset();
}
// Equivalent...
for( i = 103; i <= 105; ++i ){
q.bind(1, i).bind(2, i*2).stepReset();
}
}finally{
q.finalize();
}
log("Query data with exec() using rowMode 'array'...");
db.exec({
sql: "select a from t order by a limit 3",
rowMode: 'array', // 'array', 'object', or 'stmt' (default)
callback: function(row){
log("row ",++this.counter,"=",row);
}.bind({counter: 0})
});
log("Query data with exec() using rowMode 'object'...");
db.exec({
sql: "select a as aa, b as bb from t order by aa limit 3",
rowMode: 'object',
callback: function(row){
log("row ",++this.counter,"=",row);
}.bind({counter: 0})
});
log("Query data with exec() using rowMode 'stmt'...");
db.exec({
sql: "select a from t order by a limit 3",
rowMode: 'stmt', // stmt === the default
callback: function(row){
log("row ",++this.counter,"get(0) =",row.get(0));
}.bind({counter: 0})
});
log("Query data with exec() using rowMode INTEGER (result column index)...");
db.exec({
sql: "select a, b from t order by a limit 3",
rowMode: 1, // === result column 1
callback: function(row){
log("row ",++this.counter,"b =",row);
}.bind({counter: 0})
});
log("Query data with exec() without a callback...");
let resultRows = [];
db.exec({
sql: "select a, b from t order by a limit 3",
rowMode: 'object',
resultRows: resultRows
});
log("Result rows:",resultRows);
log("Create a scalar UDF...");
db.createFunction({
name: 'twice',
callback: function(arg){ // note the call arg count
return arg + arg;
}
});
log("Run scalar UDF and collect result column names...");
let columnNames = [];
db.exec({
sql: "select a, twice(a), twice(''||a) from t order by a desc limit 3",
columnNames: columnNames,
callback: function(row){
log("a =",row.get(0), "twice(a) =", row.get(1), "twice(''||a) =",row.get(2));
}
});
log("Result column names:",columnNames);
/**
Main differences between exec() and execMulti():
- execMulti() traverses all statements in the input SQL
- exec() supports a couple options not supported by execMulti(),
and vice versa.
- execMulti() result callback/array only activates for the
first statement which has result columns. It is arguable
whether it should support a callback at all, and that
feature may be removed.
- execMulti() column-bind data only activates for the first statement
with bindable columns. This feature is arguable and may be removed.
*/
if(0){
warn("UDF will throw because of incorrect arg count...");
db.exec("select twice(1,2,3)");
}
try {
db.callInTransaction( function(D) {
D.exec("delete from t");
log("In transaction: count(*) from t =",db.selectValue("select count(*) from t"));
throw new sqlite3.SQLite3Error("Demonstrating callInTransaction() rollback");
});
}catch(e){
log("Got expected exception:",e.message);
log("count(*) from t =",db.selectValue("select count(*) from t"));
}
}finally{
db.close();
}
/**
Misc. DB features:
- get change count (total or statement-local, 32- or 64-bit)
- get its file name
- selectValue() takes SQL and returns first column of first row.
Misc. Stmt features:
- Various forms of bind()
- clearBindings()
- reset()
- Various forms of step()
- Variants of get() for explicit type treatment/conversion,
e.g. getInt(), getFloat(), getBlob(), getJSON()
- getColumnName(ndx), getColumnNames()
- getParamIndex(name)
*/
}/*demo1()*/;
const runDemos = function(Module){
//log("Module",Module);
const sqlite3 = Module.sqlite3,
capi = sqlite3.capi,
oo = sqlite3.oo1,
wasm = capi.wasm;
log("Loaded module:",capi.sqlite3_libversion(), capi.sqlite3_sourceid());
log("sqlite3 namespace:",sqlite3);
try {
[ demo1 ].forEach((f)=>f(sqlite3, Module))
}catch(e){
error("Exception:",e.message);
throw e;
}
};
sqlite3InitModule(self.sqlite3TestModule).then(runDemos);
})();
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