Sqlite example update (#348)

* added descriptions of the steps required to run the example

* added an overview section

* rephrased a bit in the overview section

* rephrased a bit in the sqlite example section

Co-authored-by: igor <dev@igor.sh>

marine-examples/README.md

@@ -198,7 +198,7 @@ You can build, inspect and test the project as outlined in the [Greeting Example
 
 ## SQLite Example
 
-[SQLite](https://www.sqlite.org/index.html) is an ubiquitous persistence solution also available on the Fluence stack. Unlike basic compute modules, creating an SQLite service is a little more intricate. In order to create the service, we need two dependencies: An SQLite Wasm module and an SQLite adapter, where the adapter is a [WASM IT compliant](https://crates.io/crates/marine-sqlite-connector) [sqlite](https://github.com/stainless-steel/sqlite) package implementation. The SQLite Wasm module can be obtain from the repo as a [release](https://github.com/fluencelabs/sqlite/releases/tag/v0.15.0_w) or compiled from [code](https://github.com/fluencelabs/sqlite).  For the purpose of this example, we use the release version -- see `build.sh`.
+[SQLite](https://www.sqlite.org/index.html) is an ubiquitous persistence solution also available on the Fluence stack. Unlike basic compute modules, using SQLite in a service is a little more intricate. In order to create the service, we need two dependencies: An SQLite Wasm module and an SQLite adapter, where the adapter is a [WASM IT compliant](https://crates.io/crates/marine-sqlite-connector) [sqlite](https://github.com/stainless-steel/sqlite) package implementation. The SQLite Wasm module can be obtain from the repo as a [release](https://github.com/fluencelabs/sqlite/releases/tag/v0.15.0_w) or compiled from [code](https://github.com/fluencelabs/sqlite).  For the purpose of this example, we use the release version -- see `build.sh`.
 
 As a result, our service is comprised of two modules: the SQLite Wasm module and our sqlite module. The Rust code, see `src/main.rs` is pretty standard fare but our config file changes signficiantly:
 

marine-examples/sqlite/README.md

@@ -0,0 +1,115 @@
+# SQLite Example
+
+## Overview
+
+[SQLite](https://www.sqlite.org/index.html) is an ubiquitous persistence solution also available on the Fluence stack. Unlike basic compute modules, using SQLite in a service is a little more intricate. In order to create the service, we need two dependencies: An SQLite Wasm module and an SQLite adapter, where the adapter is a [WASM IT compliant](https://crates.io/crates/marine-sqlite-connector) [sqlite](https://github.com/stainless-steel/sqlite) package implementation. The SQLite Wasm module can be obtain from the repo as a [release](https://github.com/fluencelabs/sqlite/releases/tag/v0.15.0_w) or compiled from [code](https://github.com/fluencelabs/sqlite).  For the purpose of this example, we use the release version -- see `build.sh`.
+
+As a result, our service is comprised of two modules: the SQLite Wasm module and our sqlite module. 
+
+## Build
+
+To build the required artifacts, please run the following command:
+
+```
+./build.sh
+```
+
+Upon a successful build it results a couple of wasm modules:
+
+```
+➜  sqlite git:(main) ls artifacts
+sqlite3.wasm     sqlite_test.wasm
+```
+
+## Run
+
+To check how it works, we need to run `mrepl`:
+
+```
+➜  sqlite git:(main) mrepl Config.toml
+Welcome to the Marine REPL (version 0.16.1)
+Minimal supported versions
+  sdk: 0.6.0
+  interface-types: 0.20.0
+
+New version is available! 0.16.1 -> 0.16.2
+To update run: cargo +nightly install mrepl
+
+app service was created with service id = e593c776-494a-4012-9020-5b50f44409d8
+elapsed time 2.555104035s
+
+1> i
+Loaded modules interface:
+data DBOpenDescriptor:
+  ret_code: i32
+  db_handle: u32
+data DBPrepareDescriptor:
+  ret_code: i32
+  stmt_handle: u32
+  tail: u32
+data DBExecDescriptor:
+  ret_code: i32
+  err_msg: string
+
+sqlite_test:
+  fn test2(age: i64)
+  fn test1(age: i64)
+  fn test3()
+  fn test_last_rowid() -> i64
+sqlite3:
+  fn sqlite3_errmsg(db_handle: u32) -> string
+  fn sqlite3_open_v2(filename: string, flags: i32, vfs: string) -> DBOpenDescriptor
+  fn sqlite3_bind_double(stmt_handle: u32, pos: i32, value: f64) -> i32
+  fn sqlite3_column_count(stmt_handle: u32) -> i32
+  fn sqlite3_bind_text(stmt_handle: u32, pos: i32, text: string, xDel: i32) -> i32
+  fn sqlite3_errcode(db: u32) -> i32
+  fn sqlite3_busy_timeout(db_handle: u32, ms: u32) -> i32
+  fn sqlite3_changes(db_handle: u32) -> i32
+  fn sqlite3_column_name(stmt_handle: u32, N: u32) -> string
+  fn sqlite3_column_int64(stmt_handle: u32, icol: u32) -> i64
+  fn sqlite3_bind_blob(stmt_handle: u32, pos: i32, blob: []u8, xDel: i32) -> i32
+  fn sqlite3_finalize(stmt_handle: u32) -> i32
+  fn sqlite3_column_type(stmt_handle: u32, icol: u32) -> i32
+  fn sqlite3_prepare_v2(db_handle: u32, sql: string) -> DBPrepareDescriptor
+  fn sqlite3_column_bytes(stmt_handle: u32, icol: u32) -> i32
+  fn sqlite3_column_text(stmt_handle: u32, icol: u32) -> string
+  fn sqlite3_column_blob(stmt_handle: u32, icol: i32) -> []u8
+  fn sqlite3_column_double(stmt_handle: u32, icol: i32) -> f64
+  fn sqlite3_close(db_handle: u32) -> i32
+  fn sqlite3_exec(db_handle: u32, sql: string, callback_id: i32, callback_arg: i32) -> DBExecDescriptor
+  fn sqlite3_total_changes(db_handle: u32) -> i32
+  fn sqlite3_bind_null(stmt_handle: u32, pos: i32) -> i32
+  fn sqlite3_libversion_number() -> i32
+  fn sqlite3_reset(stmt_handle: u32) -> i32
+  fn sqlite3_step(stmt_handle: u32) -> i32
+  fn sqlite3_bind_int64(stmt_handle: u32, pos: i32, value: i64) -> i32
+
+2> call sqlite_test test1 [20]
+name = Alice
+age = 42
+name = Bob
+age = 69
+result: Null
+ elapsed time: 37.443512ms
+
+3> call sqlite_test test2 [20]
+name = Alice
+age = 42
+name = Bob
+age = 69
+result: Null
+ elapsed time: 1.715774ms
+
+4> call sqlite_test test3 []
+table size is: 2
+result: Null
+ elapsed time: 110.686235ms
+
+5> call sqlite_test test_last_rowid []
+result: Number(4)
+ elapsed time: 39.816385ms
+
+6> q
+```
+
+For more detailed and in depth reading on the example please refer to the [Marine Examples Readme](../README.md#sqlite-example)