Add check "Do not index booleans" (#377)

* Add IndexWithColumns to the model and a new check INDEXES_WITH_BOOLEAN

* Fix checkstyle

* Add tests

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/column/Column.java

@@ -30,6 +30,13 @@ public class Column implements DbObject, ColumnNameAware, Comparable<Column> {
     private final String columnName;
     private final boolean notNull;
 
+    /**
+     * Constructs a {@code Column} object.
+     *
+     * @param tableName  table name; should be non-blank.
+     * @param columnName column name; should be non-blank.
+     * @param notNull    whether column is not null or nullable
+     */
     protected Column(@Nonnull final String tableName,
                      @Nonnull final String columnName,
                      final boolean notNull) {
@@ -126,11 +133,25 @@ public int compareTo(@Nonnull final Column other) {
         return Boolean.compare(notNull, other.notNull);
     }
 
+    /**
+     * Constructs a not null {@code Column} object.
+     *
+     * @param tableName  table name; should be non-blank.
+     * @param columnName column name; should be non-blank.
+     * @return {@code Column}
+     */
     @Nonnull
     public static Column ofNotNull(@Nonnull final String tableName, @Nonnull final String columnName) {
         return new Column(tableName, columnName, true);
     }
 
+    /**
+     * Constructs a nullable {@code Column} object.
+     *
+     * @param tableName  table name; should be non-blank.
+     * @param columnName column name; should be non-blank.
+     * @return {@code Column}
+     */
     @Nonnull
     public static Column ofNullable(@Nonnull final String tableName, @Nonnull final String columnName) {
         return new Column(tableName, columnName, false);

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/column/ColumnWithSerialType.java

@@ -25,7 +25,7 @@
  * @since 0.6.2
  */
 @Immutable
-public class ColumnWithSerialType implements DbObject, ColumnNameAware, Comparable<ColumnWithSerialType> {
+public final class ColumnWithSerialType implements DbObject, ColumnNameAware, Comparable<ColumnWithSerialType> {
 
     private final Column column;
     private final SerialType serialType;
@@ -44,7 +44,7 @@ private ColumnWithSerialType(@Nonnull final Column column,
      */
     @Nonnull
     @Override
-    public final String getName() {
+    public String getName() {
         return column.getName();
     }
 
@@ -110,7 +110,7 @@ public String toString() {
      * {@inheritDoc}
      */
     @Override
-    public final boolean equals(final Object other) {
+    public boolean equals(final Object other) {
         if (this == other) {
             return true;
         }
@@ -129,7 +129,7 @@ public final boolean equals(final Object other) {
      * {@inheritDoc}
      */
     @Override
-    public final int hashCode() {
+    public int hashCode() {
         return Objects.hash(column, serialType, sequenceName);
     }
 
@@ -148,25 +148,54 @@ public int compareTo(@Nonnull final ColumnWithSerialType other) {
         return sequenceName.compareTo(other.sequenceName);
     }
 
+    /**
+     * Constructs a {@code ColumnWithSerialType} object of given serial type.
+     *
+     * @param column       column; should be non-null.
+     * @param serialType   column serial type; should be non-null.
+     * @param sequenceName sequence name; should be non-blank.
+     * @return {@code ColumnWithSerialType}
+     */
     @Nonnull
     public static ColumnWithSerialType of(@Nonnull final Column column,
                                           @Nonnull final SerialType serialType,
                                           @Nonnull final String sequenceName) {
         return new ColumnWithSerialType(column, serialType, sequenceName);
     }
 
+    /**
+     * Constructs a {@code ColumnWithSerialType} object of {@code bigserial} type.
+     *
+     * @param column       column; should be non-null.
+     * @param sequenceName sequence name; should be non-blank.
+     * @return {@code ColumnWithSerialType}
+     */
     @Nonnull
     public static ColumnWithSerialType ofBigSerial(@Nonnull final Column column,
                                                    @Nonnull final String sequenceName) {
         return of(column, SerialType.BIG_SERIAL, sequenceName);
     }
 
+    /**
+     * Constructs a {@code ColumnWithSerialType} object of {@code serial} type.
+     *
+     * @param column       column; should be non-null.
+     * @param sequenceName sequence name; should be non-blank.
+     * @return {@code ColumnWithSerialType}
+     */
     @Nonnull
     public static ColumnWithSerialType ofSerial(@Nonnull final Column column,
                                                 @Nonnull final String sequenceName) {
         return of(column, SerialType.SERIAL, sequenceName);
     }
 
+    /**
+     * Constructs a {@code ColumnWithSerialType} object of {@code smallserial} type.
+     *
+     * @param column       column; should be non-null.
+     * @param sequenceName sequence name; should be non-blank.
+     * @return {@code ColumnWithSerialType}
+     */
     @Nonnull
     public static ColumnWithSerialType ofSmallSerial(@Nonnull final Column column,
                                                      @Nonnull final String sequenceName) {

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/index/Index.java

@@ -73,7 +73,13 @@ public String toString() {
         return Index.class.getSimpleName() + '{' + innerToString() + '}';
     }
 
+    /**
+     * An auxiliary utility method for implementing {@code toString()} in child classes.
+     *
+     * @return string representation of the internal fields of this class
+     */
     @SuppressWarnings("WeakerAccess")
+    @Nonnull
     protected String innerToString() {
         return "tableName='" + tableName + '\'' +
                 ", indexName='" + indexName + '\'';

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/index/IndexWithBloat.java

@@ -52,6 +52,10 @@ public int getBloatPercentage() {
         return bloatPercentage;
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    @Nonnull
     @Override
     protected String innerToString() {
         return super.innerToString() + ", bloatSizeInBytes=" + bloatSizeInBytes +

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/index/IndexWithColumns.java

@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2019-2024. Ivan Vakhrushev and others.
+ * https://github.com/mfvanek/pg-index-health
+ *
+ * This file is a part of "pg-index-health" - a Java library for
+ * analyzing and maintaining indexes health in PostgreSQL databases.
+ *
+ * Licensed under the Apache License 2.0
+ */
+
+package io.github.mfvanek.pg.model.index;
+
+import io.github.mfvanek.pg.model.column.Column;
+import io.github.mfvanek.pg.model.validation.Validators;
+
+import java.util.List;
+import java.util.Objects;
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Represents database index with information about size and columns.
+ *
+ * @author Ivan Vahrushev
+ * @since 0.10.4
+ */
+@Immutable
+public class IndexWithColumns extends IndexWithSize {
+
+    private final List<Column> columns;
+
+    @SuppressWarnings("WeakerAccess")
+    protected IndexWithColumns(@Nonnull final String tableName,
+                               @Nonnull final String indexName,
+                               final long indexSizeInBytes,
+                               @Nonnull final List<Column> columns) {
+        super(tableName, indexName, indexSizeInBytes);
+        final List<Column> defensiveCopy = List.copyOf(Objects.requireNonNull(columns, "columns cannot be null"));
+        Validators.validateThatTableIsTheSame(tableName, defensiveCopy);
+        this.columns = defensiveCopy;
+    }
+
+    /**
+     * Gets columns in index.
+     *
+     * @return list of columns
+     */
+    @Nonnull
+    public List<Column> getColumns() {
+        return columns;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Nonnull
+    @Override
+    protected String innerToString() {
+        return super.innerToString() + ", columns=" + columns;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Nonnull
+    @Override
+    public String toString() {
+        return IndexWithColumns.class.getSimpleName() + '{' + innerToString() + '}';
+    }
+
+    /**
+     * Constructs an {@code IndexWithColumns} object with one column.
+     *
+     * @param tableName        table name; should be non-blank.
+     * @param indexName        index name; should be non-blank.
+     * @param indexSizeInBytes index size in bytes; should be positive or zero.
+     * @param column           column in index.
+     * @return {@code IndexWithColumns}
+     */
+    @Nonnull
+    public static IndexWithColumns ofSingle(@Nonnull final String tableName,
+                                            @Nonnull final String indexName,
+                                            final long indexSizeInBytes,
+                                            @Nonnull final Column column) {
+        final List<Column> columns = List.of(Objects.requireNonNull(column, "column cannot be null"));
+        return new IndexWithColumns(tableName, indexName, indexSizeInBytes, columns);
+    }
+
+    /**
+     * Constructs an {@code IndexWithColumns} object with given columns.
+     *
+     * @param tableName        table name; should be non-blank.
+     * @param indexName        index name; should be non-blank.
+     * @param indexSizeInBytes index size in bytes; should be positive or zero.
+     * @param columns          columns in index.
+     * @return {@code IndexWithColumns}
+     */
+    @Nonnull
+    public static IndexWithColumns ofColumns(@Nonnull final String tableName,
+                                             @Nonnull final String indexName,
+                                             final long indexSizeInBytes,
+                                             @Nonnull final List<Column> columns) {
+        return new IndexWithColumns(tableName, indexName, indexSizeInBytes, columns);
+    }
+}

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/index/IndexWithNulls.java

@@ -11,31 +11,36 @@
 package io.github.mfvanek.pg.model.index;
 
 import io.github.mfvanek.pg.model.column.Column;
-import io.github.mfvanek.pg.model.validation.Validators;
 
 import java.util.List;
 import java.util.Objects;
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.Immutable;
 
+/**
+ * Represents database index with information about size and nullable columns.
+ *
+ * @author Ivan Vahrushev
+ * @since 0.0.1
+ */
 @Immutable
-public final class IndexWithNulls extends IndexWithSize {
-
-    private final Column nullableColumn;
+public final class IndexWithNulls extends IndexWithColumns {
 
     private IndexWithNulls(@Nonnull final String tableName,
                            @Nonnull final String indexName,
                            final long indexSizeInBytes,
                            @Nonnull final Column nullableColumn) {
-        super(tableName, indexName, indexSizeInBytes);
-        Objects.requireNonNull(nullableColumn, "nullableColumn cannot be null");
-        Validators.validateThatTableIsTheSame(tableName, List.of(nullableColumn));
-        this.nullableColumn = nullableColumn;
+        super(tableName, indexName, indexSizeInBytes, List.of(Objects.requireNonNull(nullableColumn, "nullableColumn cannot be null")));
     }
 
+    /**
+     * Gets nullable column in index.
+     *
+     * @return nullable column
+     */
     @Nonnull
     public Column getNullableColumn() {
-        return nullableColumn;
+        return getColumns().get(0);
     }
 
     /**
@@ -44,11 +49,19 @@ public Column getNullableColumn() {
     @Nonnull
     @Override
     public String toString() {
-        return IndexWithNulls.class.getSimpleName() + '{' +
-                innerToString() +
-                ", nullableColumn=" + nullableColumn + '}';
+        return IndexWithNulls.class.getSimpleName() + '{' + innerToString() + '}';
     }
 
+    /**
+     * Constructs an {@code IndexWithNulls} object.
+     *
+     * @param tableName          table name; should be non-blank.
+     * @param indexName          index name; should be non-blank.
+     * @param indexSizeInBytes   index size in bytes; should be positive or zero.
+     * @param nullableColumnName nullable column in this index.
+     * @return {@code IndexWithNulls}
+     */
+    @Nonnull
     public static IndexWithNulls of(@Nonnull final String tableName,
                                     @Nonnull final String indexName,
                                     final long indexSizeInBytes,

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/index/IndexWithSize.java

@@ -15,6 +15,12 @@
 import javax.annotation.Nonnull;
 import javax.annotation.concurrent.Immutable;
 
+/**
+ * Represents database index with information about size.
+ *
+ * @author Ivan Vahrushev
+ * @since 0.0.1
+ */
 @Immutable
 public class IndexWithSize extends Index implements IndexSizeAware {
 
@@ -36,6 +42,10 @@ public long getIndexSizeInBytes() {
         return indexSizeInBytes;
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    @Nonnull
     @Override
     protected String innerToString() {
         return super.innerToString() + ", indexSizeInBytes=" + indexSizeInBytes;
@@ -50,6 +60,15 @@ public String toString() {
         return IndexWithSize.class.getSimpleName() + '{' + innerToString() + '}';
     }
 
+    /**
+     * Constructs an {@code IndexWithSize} object.
+     *
+     * @param tableName        table name; should be non-blank.
+     * @param indexName        index name; should be non-blank.
+     * @param indexSizeInBytes index size in bytes; should be positive or zero.
+     * @return {@code IndexWithSize}
+     */
+    @Nonnull
     public static IndexWithSize of(@Nonnull final String tableName,
                                    @Nonnull final String indexName,
                                    final long indexSizeInBytes) {

pg-index-health-model/src/main/java/io/github/mfvanek/pg/model/table/Table.java

@@ -59,6 +59,12 @@ public long getTableSizeInBytes() {
         return tableSizeInBytes;
     }
 
+    /**
+     * An auxiliary utility method for implementing {@code toString()} in child classes.
+     *
+     * @return string representation of the internal fields of this class
+     */
+    @Nonnull
     final String innerToString() {
         return "tableName='" + tableName + '\'' +
                 ", tableSizeInBytes=" + tableSizeInBytes;