knex/src/dialects/sqlite3/schema/ddl.js

// SQLite3_DDL
//
// All of the SQLite3 specific DDL helpers for renaming/dropping
// columns and changing datatypes.
// -------

var Promise = require('../../../promise');
import {assign, uniqueId, find, map, omit} from 'lodash'

// So altering the schema in SQLite3 is a major pain.
// We have our own object to deal with the renaming and altering the types
// for sqlite3 things.
function SQLite3_DDL(client, tableCompiler, pragma, connection) {
  this.client        = client
  this.tableCompiler = tableCompiler;
  this.pragma        = pragma;
  this.tableName     = this.tableCompiler.tableNameRaw;
  this.alteredName   = uniqueId('_knex_temp_alter');
  this.connection    = connection
}

assign(SQLite3_DDL.prototype, {

  getColumn: Promise.method(function(column) {
    var currentCol = find(this.pragma, {name: column});
    if (!currentCol) throw new Error('The column ' + column + ' is not in the ' + this.tableName + ' table');
    return currentCol;
  }),

  getTableSql: function() {
    return this.trx.raw('SELECT name, sql FROM sqlite_master WHERE type="table" AND name="' + this.tableName + '"');
  },

  renameTable: Promise.method(function() {
    return this.trx.raw('ALTER TABLE "' + this.tableName + '" RENAME TO "' + this.alteredName + '"');
  }),

  dropOriginal: function() {
    return this.trx.raw('DROP TABLE "' + this.tableName + '"');
  },

  dropTempTable: function() {
    return this.trx.raw('DROP TABLE "' + this.alteredName + '"');
  },

  copyData: function() {
    return this.trx.raw('SELECT * FROM "' + this.tableName + '"')
      .bind(this)
      .then(this.insertChunked(20, this.alteredName));
  },

  reinsertData: function(iterator) {
    return function() {
      return this.trx.raw('SELECT * FROM "' + this.alteredName + '"')
        .bind(this)
        .then(this.insertChunked(20, this.tableName, iterator));
    };
  },

  insertChunked: function(amount, target, iterator) {
    iterator = iterator || function(noop) { return noop; };
    return function(result) {
      var batch = [];
      var ddl = this;
      return Promise.reduce(result, function(memo, row) {
        memo++;
        batch.push(row);
        if (memo % 20 === 0 || memo === result.length) {
          return ddl.trx.queryBuilder()
            .table(target)
            .insert(map(batch, iterator))
            .then(function() { batch = []; })
            .thenReturn(memo);
        }
        return memo;
      }, 0);
    };
  },

  createTempTable: function(createTable) {
    return function() {
      return this.trx.raw(createTable.sql.replace(this.tableName, this.alteredName));
    };
  },

  _doReplace: function (sql, from, to) {
    var matched = sql.match(/^CREATE TABLE (\S+) \((.*)\)/);

    var tableName = matched[1],
        defs = matched[2];

    if (!defs) { throw new Error('No column definitions in this statement!'); }

    var parens = 0, args = [ ], ptr = 0;
    for (var i = 0, x = defs.length; i < x; i++) {
      switch (defs[i]) {
        case '(':
          parens++;
        break;
        case ')':
          parens--;
        break;
        case ',':
          if (parens === 0) {
            args.push(defs.slice(ptr, i));
            ptr = i + 1;
          }
        break;
        case ' ':
          if (ptr === i) {
            ptr = i + 1;
          }
        break;
      }
    }
    args.push(defs.slice(ptr, i));

    args = args.map(function (item) {
      var split = item.split(' ');

      if (split[0] === from) {
        // column definition
        if (to) {
          split[0] = to;
          return split.join(' ');
        }
        return ''; // for deletions
      }

      // skip constraint name
      var idx = (/constraint/i.test(split[0]) ? 2 : 0);

      // primary key and unique constraints have one or more
      // columns from this table listed between (); replace
      // one if it matches
      if (/primary|unique/i.test(split[idx])) {
        return item.replace(/\(.*\)/, function (columns) {
          return columns.replace(from, to);
        });
      }

      // foreign keys have one or more columns from this table
      // listed between (); replace one if it matches
      // foreign keys also have a 'references' clause
      // which may reference THIS table; if it does, replace
      // column references in that too!
      if (/foreign/.test(split[idx])) {
        split = item.split(/ references /i);
        // the quoted column names save us from having to do anything
        // other than a straight replace here
        split[0] = split[0].replace(from, to);

        if (split[1].slice(0, tableName.length) === tableName) {
          split[1] = split[1].replace(/\(.*\)/, function (columns) {
            return columns.replace(from, to);
          });
        }
        return split.join(' references ');
      }

      return item;
    });
    return sql.replace(/\(.*\)/, function () {
      return '(' + args.join(', ') + ')';
    }).replace(/,\s*([,)])/, '$1');
  },

  // Boy, this is quite a method.
  renameColumn: Promise.method(function(from, to) {
    var currentCol;

    return this.client.transaction(function(trx) {
      this.trx = trx
      return this.getColumn(from)
        .bind(this)
        .tap(function(col) { currentCol = col; })
        .then(this.getTableSql)
        .then(function(sql) {
          var a = this.client.wrapIdentifier(from);
          var b = this.client.wrapIdentifier(to);
          var createTable = sql[0];
          var newSql = this._doReplace(createTable.sql, a, b);
          if (sql === newSql) {
            throw new Error('Unable to find the column to change');
          }
          return Promise.bind(this)
            .then(this.createTempTable(createTable))
            .then(this.copyData)
            .then(this.dropOriginal)
            .then(function() {
              return this.trx.raw(newSql);
            })
            .then(this.reinsertData(function(row) {
              row[to] = row[from];
              return omit(row, from);
            }))
            .then(this.dropTempTable)
        })
    }.bind(this), {connection: this.connection})
  }),

  dropColumn: Promise.method(function(column) {
    var currentCol;

    return this.client.transaction(function(trx) {
      this.trx = trx
      return this.getColumn(column).tap(function(col) {
        currentCol = col;
      })
      .bind(this)
      .then(this.getTableSql)
      .then(function(sql) {
        var createTable = sql[0];
        var a = this.client.wrapIdentifier(column);
        var newSql = this._doReplace(createTable.sql, a, '');
        if (sql === newSql) {
          throw new Error('Unable to find the column to change');
        }
        return Promise.bind(this)
          .then(this.createTempTable(createTable))
          .then(this.copyData)
          .then(this.dropOriginal)
          .then(function() {
            return this.trx.raw(newSql);
          })
          .then(this.reinsertData(function(row) {
            return omit(row, column);
          }))
          .then(this.dropTempTable);
      })
    }.bind(this), {connection: this.connection})
  })

})


module.exports = SQLite3_DDL;