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| const Helpers = require('./Helpers');
/**
* Base Database Driver
*
* @private
*/
const Driver = {
identifierStartChar: '"',
identifierEndChar: '"',
tablePrefix: null,
hasTruncate: true,
/**
* Low level function for naive quoting of strings
*
* @param {String} str - The sql fragment to quote
* @return {String} - The quoted sql fragment
* @private
*/
_quote (str) {
return (Helpers.isString(str) &&
!(str.startsWith(Driver.identifierStartChar) || str.endsWith(Driver.identifierEndChar))
)
? `${Driver.identifierStartChar}${str}${Driver.identifierEndChar}`
: str;
},
/**
* Set the limit clause
* @private
* @param {String} sql - SQL statement to modify
* @param {Number} limit - Maximum number of rows to fetch
* @param {Number} [offset] - Number of rows to skip
* @return {String} - Modified SQL statement
*/
limit (sql, limit, offset) {
sql += ` LIMIT ${limit}`;
if (Helpers.isNumber(offset)) {
sql += ` OFFSET ${offset}`;
}
return sql;
},
/**
* Quote database table name, and set prefix
*
* @private
* @param {String} table - Table name to quote
* @return {String} - Quoted table name
*/
quoteTable (table) {
// Quote after prefix
return Driver.quoteIdentifiers(table);
},
/**
* Use the driver's escape character to quote identifiers
*
* @private
* @param {String|Array} str - String or array of strings to quote identifiers
* @return {String|Array} - Quoted identifier(s)
*/
quoteIdentifiers (str) {
const pattern = new RegExp(
`${Driver.identifierStartChar}(` +
'([a-zA-Z0-9_]+)' + '(((.*?)))' +
`)${Driver.identifierEndChar}`, 'ig');
// Recurse for arrays of identifiers
if (Array.isArray(str)) {
return str.map(Driver.quoteIdentifiers);
}
// cast to string so that you don't have undefined method errors with junk data
str = String(str);
// Handle commas
if (str.includes(',')) {
const parts = str.split(',').map(Helpers.stringTrim);
str = parts.map(Driver.quoteIdentifiers).join(',');
}
// Split identifiers by period
const hierarchies = str.split('.').map(Driver._quote);
let raw = hierarchies.join('.');
// Fix functions
if (raw.includes('(') && raw.includes(')')) {
const functionCalls = pattern.exec(raw);
// Unquote the function
raw = raw.replace(functionCalls[0], functionCalls[1]);
// Quote the identifiers inside of the parens
const inParens = functionCalls[3].substring(1, functionCalls[3].length - 1);
raw = raw.replace(inParens, Driver.quoteIdentifiers(inParens));
}
return raw;
},
/**
* Generate SQL to truncate the passed table
*
* @private
* @param {String} table - Table to truncate
* @return {String} - Truncation SQL
*/
truncate (table) {
let sql = (Driver.hasTruncate)
? 'TRUNCATE '
: 'DELETE FROM ';
sql += Driver.quoteTable(table);
return sql;
},
/**
* Generate SQL to insert a group of rows
*
* @private
* @param {String} table - The table to insert to
* @param {Array} [data] - The array of object containing data to insert
* @return {String} - Query and data to insert
*/
insertBatch (table, data) {
const values = [];
const fields = Object.keys(data[0]);
let sql = '';
// Get the data values to insert, so they can
// be parameterized
data.forEach(obj => {
Object.keys(obj).forEach(key => {
values.push(obj[key]);
});
});
// Get the field names from the keys of the first
// object inserted
table = Driver.quoteTable(table);
sql += `INSERT INTO ${table} (${Driver.quoteIdentifiers(fields).join(',')}) VALUES `;
// Create placeholder groups
const params = Array(fields.length).fill('?');
const paramString = `(${params.join(',')})`;
const paramList = Array(data.length).fill(paramString);
sql += paramList.join(',');
return {
sql: sql,
values: values
};
},
/**
* Creates a batch update sql statement
*
* @private
* @param {String} table - The name of the table to update
* @param {Array<Object>} data - Array of objects containing the update data
* @param {String} updateKey - the field name to update based on
* @return {Array<String,Object,Number>} - array of parameters passed to run the query
*/
updateBatch (table, data, updateKey) {
let affectedRows = 0;
let insertData = [];
const fieldLines = [];
let sql = `UPDATE ${Driver.quoteTable(table)} SET `;
// get the keys of the current set of data, except the one used to
// set the update condition
const fields = data.reduce((previous, current) => {
affectedRows++;
const keys = Object.keys(current).filter(key => {
return key !== updateKey && !previous.includes(key);
});
return previous.concat(keys);
}, []);
// Create the CASE blocks for each data set
fields.forEach(field => {
let line = `${Driver.quoteIdentifiers(field)} = CASE\n`;
const cases = [];
data.forEach(currentCase => {
insertData.push(currentCase[updateKey]);
insertData.push(currentCase[field]);
const newCase = `WHEN ${Driver.quoteIdentifiers(updateKey)} =? THEN ? `;
cases.push(newCase);
});
line += `${cases.join('\n')}\n`;
line += `ELSE ${Driver.quoteIdentifiers(field)} END`;
fieldLines.push(line);
});
sql += `${fieldLines.join(',\n')}\n`;
const whereValues = [];
data.forEach(entry => {
const insertValue = entry[updateKey];
whereValues.push(insertValue);
insertData.push(insertValue);
});
// Create the placeholders for the WHERE IN clause
const placeholders = Array(whereValues.length);
placeholders.fill('?');
sql += `WHERE ${Driver.quoteIdentifiers(updateKey)} IN `;
sql += `( ${placeholders.join(',')} )`;
return [sql, insertData, affectedRows];
}
};
module.exports = Driver;
|