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Database-like contract using solidity
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| // SPDX-License-Identifier: MIT | |
| pragma solidity ^0.8.17; | |
| contract Database { | |
| struct Table { | |
| string[] columns; | |
| mapping(string => string[]) values; | |
| bool exists; | |
| } | |
| mapping(string => Table) table; | |
| mapping(string => bool) has; | |
| function contains( | |
| string[] memory a, | |
| string[] memory b | |
| ) private returns (bool) { | |
| for (uint i = 0; i < b.length; i++) { | |
| has[b[i]] = false; | |
| } | |
| for (uint i = 0; i < a.length; i++) { | |
| has[a[i]] = true; | |
| } | |
| bool contains_ = true; | |
| for (uint i = 0; i < b.length; i++) { | |
| contains_ = contains_ && has[b[i]]; | |
| } | |
| return contains_; | |
| } | |
| function CREATE_TABLE(string memory a, string[] memory b) public { | |
| table[a].columns = b; | |
| table[a].exists = true; | |
| } | |
| function DROP_TABLE(string memory a) public { | |
| delete table[a]; | |
| } | |
| mapping(string => string) toInsert; | |
| function INSERT( | |
| string memory tableName, | |
| string[] memory columns_, | |
| string[] memory values_ | |
| ) public { | |
| require(table[tableName].exists, "No such table"); | |
| require(columns_.length == values_.length, "Mismatched #columns and #values"); | |
| require(contains(table[tableName].columns, columns_), "No such columns"); | |
| string[] memory tableColumns = table[tableName].columns; | |
| for (uint i = 0; i < tableColumns.length; i++) { | |
| toInsert[tableColumns[i]] = ""; | |
| } | |
| for (uint i = 0; i < columns_.length; i++) { | |
| toInsert[columns_[i]] = values_[i]; | |
| } | |
| for (uint i = 0; i < tableColumns.length; i++) { | |
| table[tableName].values[tableColumns[i]].push(toInsert[tableColumns[i]]); | |
| } | |
| } | |
| mapping(string => string[]) selectResult; | |
| function SELECT( | |
| string memory tableName, | |
| string[] memory columns_ | |
| ) public returns (string[][] memory) { | |
| require(table[tableName].exists, "No such table"); | |
| require( | |
| contains(table[tableName].columns, columns_), | |
| "No such columns" | |
| ); | |
| uint size = columns_.length; | |
| string[][] memory res = new string[][](size); | |
| for (uint i = 0; i < columns_.length; i++) { | |
| res[i] = table[tableName].values[columns_[i]]; | |
| } | |
| return res; | |
| } | |
| } |
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| import { ethers } from "hardhat"; | |
| async function main() { | |
| const Database = await ethers.getContractFactory("Database") | |
| const accounts = await ethers.getSigners() | |
| const owner = accounts[0] | |
| console.log(`Database admin: ${owner.address}`) | |
| const db = await Database.deploy() | |
| console.log(`Database address: ${db.address}`) | |
| await db.CREATE_TABLE("films", ["title", "year"]) | |
| await db.INSERT("films", ["title", "year"], ["TBD", "TBD"]) | |
| await db.INSERT("films", ["title"], ["TBD"]) | |
| const data1 = (await db.SELECT("films", ["title"])).data | |
| const data = db.interface.decodeFunctionData("SELECT", data1) | |
| console.log(data) | |
| } | |
| // We recommend this pattern to be able to use async/await everywhere | |
| // and properly handle errors. | |
| main().catch((error) => { | |
| console.error(error); | |
| process.exitCode = 1; | |
| }); |
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