r2dbc module is added.

clickhouse-r2dbc/README.md

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+# clickhouse-r2dbc
+
+This module provides r2dbc support to clickhouse-jdbc driver.
+
+r2dbc link : https://r2dbc.io/
+
+Sample code: 
+```java
+ConnectionFactory connectionFactory = ConnectionFactories
+        .get("r2dbc:clickhouse:http://{username}:{password}@{host}:{port}/{database}");
+
+        Mono.from(connectionFactory.create())
+        .flatMapMany(connection -> connection
+        .createStatement("select domain, path,  toDate(cdate) as d, count(1) as count from clickdb.clicks where domain = :domain group by domain, path, d")
+        .bind("domain", domain)
+        .execute())
+        .flatMap(result -> result
+        .map((row, rowMetadata) -> String.format("%s%s[%s]:%d", row.get("domain", String.class), 
+                                                                row.get("path", String.class), 
+                                                                row.get("d", LocalDate.class), 
+                                                                row.get("count", Long.class)) ))
+        .doOnNext(System.out::println)
+        .subscribe();
+```
+
+for full example please check clickhouse-jdbc/examples/clickhouse-r2dbc-samples/clickhouse-r2dbc-spring-webflux-sample .

clickhouse-r2dbc/src/main/java/com/clickhouse/r2dbc/ClickHouseBatch.java

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+package com.clickhouse.r2dbc;
+
+import com.clickhouse.client.ClickHouseFormat;
+import com.clickhouse.client.ClickHouseRequest;
+import io.r2dbc.spi.Batch;
+import io.r2dbc.spi.Result;
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ClickHouseBatch implements Batch {
+
+    private static final ClickHouseFormat PREFERRED_FORMAT = ClickHouseFormat.TabSeparatedWithNamesAndTypes;
+    private ClickHouseRequest<?> request;
+    final List<String> sqlList;
+
+    public ClickHouseBatch(ClickHouseRequest<?> request) {
+        this.request = request;
+        this.sqlList = new ArrayList<>();
+    }
+
+    @Override
+    public Batch add(String sql) {
+        sqlList.add(sql);
+        return this;
+    }
+
+    @Override
+    public Publisher<? extends Result> execute() {
+        return Flux.fromStream(sqlList.stream().map(sql -> {
+            request.query(sql).format(PREFERRED_FORMAT);
+            return Mono.fromFuture(request::execute); }))
+                .flatMap(Mono::flux)
+                .map(ClickHouseResult::new);
+    }
+}

clickhouse-r2dbc/src/main/java/com/clickhouse/r2dbc/ClickHouseColumnMetadata.java

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+package com.clickhouse.r2dbc;
+
+import com.clickhouse.client.ClickHouseColumn;
+import com.clickhouse.r2dbc.types.ClickHouseDataTypeWrapper;
+import io.r2dbc.spi.ColumnMetadata;
+import io.r2dbc.spi.Type;
+
+public class ClickHouseColumnMetadata implements ColumnMetadata {
+
+    final Type type;
+    final String name;
+
+    ClickHouseColumnMetadata(ClickHouseColumn col) {
+        this.name = col.getColumnName(); // TODO :check alias handling.
+        this.type = ClickHouseDataTypeWrapper.of(col.getDataType());
+    }
+
+    @Override
+    public Type getType() {
+        return type;
+    }
+
+    @Override
+    public String getName() {
+        return name;
+    }
+}

clickhouse-r2dbc/src/main/java/com/clickhouse/r2dbc/ClickHouseResult.java

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+package com.clickhouse.r2dbc;
+
+import com.clickhouse.client.ClickHouseResponse;
+import com.clickhouse.client.ClickHouseResponseSummary;
+import com.clickhouse.client.logging.Logger;
+import com.clickhouse.client.logging.LoggerFactory;
+import io.r2dbc.spi.Result;
+import io.r2dbc.spi.Row;
+import io.r2dbc.spi.RowMetadata;
+import org.apache.commons.lang3.tuple.Pair;
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.function.Predicate;
+import java.util.stream.StreamSupport;
+
+public class ClickHouseResult implements Result {
+
+    private static final Logger log = LoggerFactory.getLogger(ClickHouseResult.class);
+
+    private final Flux<? extends Result.Segment> rowSegments;
+    private final Mono<? extends Result.Segment> updatedCount;
+    private final Flux<? extends Result.Segment> segments;
+
+    ClickHouseResult(ClickHouseResponse response) {
+        this.rowSegments = Mono.just(response)
+                .flatMapMany(resp -> Flux
+                        .fromStream(StreamSupport.stream(resp.records().spliterator(), false)
+                                .map(rec -> Pair.of(resp.getColumns(), rec))))
+                    .map(pair -> new ClickHouseRow(pair.getRight(), pair.getLeft()))
+                .map(RowSegment::new);
+        this.updatedCount =  Mono.just(response).map(ClickHouseResponse::getSummary)
+                .map(ClickHouseResponseSummary::getProgress)
+                .map(ClickHouseResponseSummary.Progress::getWrittenRows)
+                .map(UpdateCount::new);
+        this.segments = Flux.concat(this.updatedCount, this.rowSegments);
+    }
+
+    ClickHouseResult(Flux<? extends Result.Segment> rowSegments, Mono<? extends Result.Segment> updatedCount) {
+        this.rowSegments = rowSegments;
+        this.updatedCount = updatedCount;
+        this.segments = Flux.concat(this.updatedCount, this.rowSegments);
+    }
+
+    /**
+     * Returns updated count(written rows from summary of {@link ClickHouseResponse}).Important! if writtenRows is greater than MAX_INT then it will return MAX_INT.
+     *
+     * @return updated count
+     */
+    @Override
+    public Mono<Long> getRowsUpdated() {
+        return updatedCount.map(val -> ((UpdateCount) val).value());
+    }
+
+    @Override
+    public <T> Publisher<T> map(BiFunction<Row, RowMetadata, ? extends T> biFunction) {
+        return rowSegments.cast(RowSegment.class)
+                .map(RowSegment::row).handle((row, sink) -> {
+            try {
+                sink.next(biFunction.apply(row, row.getMetadata()));
+            } catch (Exception e) {
+                log.error("Provided function caused exception:", e);
+            }
+        });
+    }
+
+    @Override
+    public Result filter(Predicate<Segment> predicate) {
+        return new ClickHouseResult(segments.filter(predicate), updatedCount.filter(predicate));
+    }
+
+    @Override
+    public <T> Publisher<T> flatMap(Function<Segment, ? extends Publisher<? extends T>> function) {
+        return segments.flatMap(segment -> {
+            try {
+                Publisher<? extends T> retValue = function.apply(segment);
+                if (retValue == null) {
+                    return Mono.error(new IllegalStateException("flatmap function returned null value"));
+                }
+                return retValue;
+            } catch (Exception e) {
+                log.error("Provided function caused exception:", e);
+                return Mono.error(e);
+            }
+        });
+    }
+
+
+    class RowSegment implements Result.RowSegment {
+
+        final ClickHouseRow row;
+
+        RowSegment(ClickHouseRow row) {
+            this.row = row;
+        }
+
+        @Override
+        public Row row() {
+            return row;
+        }
+    }
+
+    class UpdateCount implements Result.UpdateCount {
+
+        final long updateCount;
+
+        UpdateCount(long updateCount) {
+            this.updateCount = updateCount;
+        }
+
+        @Override
+        public long value() {
+            return updateCount;
+        }
+    }
+}

clickhouse-r2dbc/src/main/java/com/clickhouse/r2dbc/ClickHouseRow.java

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+package com.clickhouse.r2dbc;
+
+import com.clickhouse.client.ClickHouseColumn;
+import com.clickhouse.client.ClickHouseRecord;
+import io.r2dbc.spi.Row;
+import io.r2dbc.spi.RowMetadata;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class ClickHouseRow implements Row {
+
+    final ClickHouseRecord record;
+    final ClickHouseRowMetadata rowMetadata;
+
+    ClickHouseRow(ClickHouseRecord record, List<ClickHouseColumn> columnList) {
+        this.record = record;
+        this.rowMetadata = new ClickHouseRowMetadata(columnList.stream()
+                .map(ClickHouseColumnMetadata::new)
+                .collect(Collectors
+                        .toMap(ClickHouseColumnMetadata::getName,
+                                Function.identity(),
+                                (v1,v2) -> v2, // since every key will be unique, won't need to merge so just overwrite with the latest one.
+                                LinkedHashMap::new)));
+    }
+
+    @Override
+    public RowMetadata getMetadata() {
+        return rowMetadata;
+    }
+
+    @Override
+    public <T> T get(int i, Class<T> aClass) {
+        return aClass.cast(record.getValue(i).asObject(aClass));
+    }
+
+    @Override
+    public <T> T get(String name, Class<T> aClass) {
+        try {
+            return aClass.cast(record.getValue(name).asObject(aClass));
+        } catch (IllegalArgumentException e) {
+            throw new NoSuchElementException(String.format("Unknown element with a name %s", name));
+        }
+    }
+}

clickhouse-r2dbc/src/main/java/com/clickhouse/r2dbc/ClickHouseRowMetadata.java

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+package com.clickhouse.r2dbc;
+
+import io.r2dbc.spi.ColumnMetadata;
+import io.r2dbc.spi.RowMetadata;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+
+public class ClickHouseRowMetadata implements RowMetadata {
+
+    LinkedHashMap<String, ClickHouseColumnMetadata> columnNameMetadataMap;
+
+    ClickHouseRowMetadata( LinkedHashMap<String, ClickHouseColumnMetadata> columnNameMetadataMap) {
+        this.columnNameMetadataMap = columnNameMetadataMap;
+    }
+
+    @Override
+    public ColumnMetadata getColumnMetadata(int i) {
+        if (i > columnNameMetadataMap.size())
+            throw new IllegalArgumentException("Given index is greater than size column metadata array.");
+        return columnNameMetadataMap.entrySet().stream().skip(i-1).findFirst().get().getValue();
+    }
+
+    @Override
+    public ColumnMetadata getColumnMetadata(String columnName) {
+        return columnNameMetadataMap.get(columnName);
+    }
+
+    @Override
+    public List<? extends ColumnMetadata> getColumnMetadatas() {
+        return Collections.unmodifiableList(new ArrayList<>(columnNameMetadataMap.values()));
+    }
+}