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JDBC Type 4 driver for MySQL.
There is a newer version: 9.1.0
/*
 * Copyright (c) 2016, 2024, Oracle and/or its affiliates.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2.0, as published by
 * the Free Software Foundation.
 *
 * This program is designed to work with certain software that is licensed under separate terms, as designated in a particular file or component or in
 * included license documentation. The authors of MySQL hereby grant you an additional permission to link the program and your derivative works with the
 * separately licensed software that they have either included with the program or referenced in the documentation.
 *
 * Without limiting anything contained in the foregoing, this file, which is part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
 * version 1.0, a copy of which can be found at http://oss.oracle.com/licenses/universal-foss-exception.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0, for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

package com.mysql.cj.result;

import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

import com.mysql.cj.protocol.ColumnDefinition;

/**
 * Protocol::ColumnDefinition41 object
 *
 */
public class DefaultColumnDefinition implements ColumnDefinition {

    protected Field[] fields;

    /** Map column names (and all of their permutations) to column indices */
    private Map columnLabelToIndex = null;

    /**
     * The above map is a case-insensitive tree-map, it can be slow, this caches lookups into that map, because the other alternative is to create new
     * object instances for every call to findColumn()....
     */
    private Map columnToIndexCache = new HashMap<>();

    /** Map of fully-specified column names to column indices */
    private Map fullColumnNameToIndex = null;

    /** Map column names (and all of their permutations) to column indices */
    private Map columnNameToIndex = null;

    private boolean builtIndexMapping = false;

    public DefaultColumnDefinition() {
    }

    public DefaultColumnDefinition(Field[] fields) {
        this.fields = fields;
    }

    @Override
    public Field[] getFields() {
        return this.fields;
    }

    @Override
    public void setFields(Field[] fields) {
        this.fields = fields;
    }

    @Override

    /**
     * Builds a hash between column names and their indices for fast retrieval.
     */
    public void buildIndexMapping() {
        int numFields = this.fields.length;
        this.columnLabelToIndex = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
        this.fullColumnNameToIndex = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
        this.columnNameToIndex = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);

        // We do this in reverse order, so that the 'first' column with a given name ends up as the final mapping in the hashtable...
        //
        // Quoting the JDBC Spec:
        //
        // "Column names used as input to getter methods are case insensitive. When a getter method is called with a column name and several columns have the
        // same name, the value of the first matching column will be returned. "
        //
        for (int i = numFields - 1; i >= 0; i--) {
            Integer index = Integer.valueOf(i);
            String columnName = this.fields[i].getOriginalName();
            String columnLabel = this.fields[i].getName();
            String fullColumnName = this.fields[i].getFullName();

            if (columnLabel != null) {
                this.columnLabelToIndex.put(columnLabel, index);
            }

            if (fullColumnName != null) {
                this.fullColumnNameToIndex.put(fullColumnName, index);
            }

            if (columnName != null) {
                this.columnNameToIndex.put(columnName, index);
            }
        }

        // set the flag to prevent rebuilding...
        this.builtIndexMapping = true;
    }

    @Override
    public boolean hasBuiltIndexMapping() {
        return this.builtIndexMapping;
    }

    @Override
    public Map getColumnLabelToIndex() {
        return this.columnLabelToIndex;
    }

    @Override
    public void setColumnLabelToIndex(Map columnLabelToIndex) {
        this.columnLabelToIndex = columnLabelToIndex;
    }

    @Override
    public Map getFullColumnNameToIndex() {
        return this.fullColumnNameToIndex;
    }

    @Override
    public void setFullColumnNameToIndex(Map fullColNameToIndex) {
        this.fullColumnNameToIndex = fullColNameToIndex;
    }

    @Override
    public Map getColumnNameToIndex() {
        return this.columnNameToIndex;
    }

    @Override
    public void setColumnNameToIndex(Map colNameToIndex) {
        this.columnNameToIndex = colNameToIndex;
    }

    @Override
    public Map getColumnToIndexCache() {
        return this.columnToIndexCache;
    }

    @Override
    public void setColumnToIndexCache(Map columnToIndexCache) {
        this.columnToIndexCache = columnToIndexCache;
    }

    @Override
    public void initializeFrom(ColumnDefinition columnDefinition) {
        this.fields = columnDefinition.getFields();
        this.columnLabelToIndex = columnDefinition.getColumnNameToIndex();
        this.fullColumnNameToIndex = columnDefinition.getFullColumnNameToIndex();
        this.builtIndexMapping = true;
    }

    @Override
    public void exportTo(ColumnDefinition columnDefinition) {
        columnDefinition.setFields(this.fields);
        columnDefinition.setColumnNameToIndex(this.columnLabelToIndex);
        columnDefinition.setFullColumnNameToIndex(this.fullColumnNameToIndex);
    }

    @Override
    public int findColumn(String columnName, boolean useColumnNamesInFindColumn, int indexBase) {
        Integer index;

        if (!hasBuiltIndexMapping()) {
            buildIndexMapping();
        }

        index = this.columnToIndexCache.get(columnName);

        if (index != null) {
            return index.intValue() + indexBase;
        }

        index = this.columnLabelToIndex.get(columnName);

        if (index == null && useColumnNamesInFindColumn) {
            index = this.columnNameToIndex.get(columnName);
        }

        if (index == null) {
            index = this.fullColumnNameToIndex.get(columnName);
        }

        if (index != null) {
            this.columnToIndexCache.put(columnName, index);

            return index.intValue() + indexBase;
        }

        // Try this inefficient way, now

        for (int i = 0; i < this.fields.length; i++) {
            if (this.fields[i].getName().equalsIgnoreCase(columnName)) {
                return i + indexBase;
            } else if (this.fields[i].getFullName().equalsIgnoreCase(columnName)) {
                return i + indexBase;
            }
        }

        return -1;
    }

    /**
     * Check if fields with type BLOB, MEDIUMBLOB, LONGBLOB, TEXT, MEDIUMTEXT, LONGTEXT, or VECTOR exist in this ColumnDefinition.
     * This check is used for making a decision about whether we want to force a buffer row (better for rows with large fields).
     *
     * @return true if this ColumnDefinition has large fields
     */
    @Override
    public boolean hasLargeFields() {
        if (this.fields != null) {
            for (int i = 0; i < this.fields.length; i++) {
                switch (this.fields[i].getMysqlType()) {
                    case BLOB:
                    case MEDIUMBLOB:
                    case LONGBLOB:
                    case TEXT:
                    case MEDIUMTEXT:
                    case LONGTEXT:
                    case JSON:
                    case VECTOR:
                        return true;
                    default:
                        break;
                }
            }
        }
        return false;
    }

}