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/*
* Copyright (C) 2015 Archie L. Cobbs. All rights reserved.
*/
package org.jsimpledb.kv.spanner;
import com.google.cloud.ByteArray;
import com.google.cloud.spanner.Key;
import com.google.cloud.spanner.KeyRange;
import com.google.cloud.spanner.KeySet;
import com.google.cloud.spanner.Options;
import com.google.cloud.spanner.ReadContext;
import com.google.cloud.spanner.ResultSet;
import com.google.cloud.spanner.SpannerException;
import com.google.cloud.spanner.Statement;
import com.google.cloud.spanner.Struct;
import com.google.common.base.Preconditions;
import java.util.Arrays;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.function.Function;
import org.jsimpledb.kv.AbstractKVStore;
import org.jsimpledb.kv.CloseableKVStore;
import org.jsimpledb.kv.KVPair;
import org.jsimpledb.util.ByteUtil;
import org.jsimpledb.util.CloseableIterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Provides a (read-only) {@link org.jsimpledb.kv.KVStore} view of a {@link ReadContext}.
*
*
* For best performance, consider wrapping an instance of this class in a {@link org.jsimpledb.kv.caching.CachingKVStore}.
*
* @see ReadWriteSpannerView
*/
public class ReadOnlySpannerView extends AbstractKVStore implements CloseableKVStore {
private static final byte[] TOP = new byte[] { (byte)0xff };
private static final Key TOP_KEY = Key.of(ByteArray.copyFrom(TOP));
private static final List V_COL = Arrays.asList("val");
private static final List KV_COL = Arrays.asList("key", "val");
protected final Logger log = LoggerFactory.getLogger(this.getClass());
protected final String tableName;
protected final ReadContext context;
protected final Function exceptionMapper;
/**
* Primary constructor.
*
* @param tableName name of the Spanner database table
* @param context read context
* @param exceptionMapper mapper for any thrown {@link SpannerException}s, or null for none
* @throws IllegalArgumentException if {@code tableName} or {@code context} is null
*/
public ReadOnlySpannerView(String tableName, ReadContext context,
Function exceptionMapper) {
Preconditions.checkArgument(tableName != null);
Preconditions.checkArgument(context != null);
this.tableName = tableName;
this.context = context;
this.exceptionMapper = exceptionMapper;
}
/**
* Convenience constructor.
*
*
* Equivalent to {@code ReadOnlySpannerView(tableName, context, null)}.
*
* @param tableName name of the Spanner database table
* @param context read context
* @throws IllegalArgumentException if {@code tableName} or {@code context} is null
*/
public ReadOnlySpannerView(String tableName, ReadContext context) {
this(tableName, context, null);
}
@Override
public byte[] get(byte[] key) {
try {
final Struct row = this.context.readRow(this.tableName, Key.of(ByteArray.copyFrom(key)), V_COL);
final byte[] val = row != null ? row.getBytes(0).toByteArray() : null;
if (this.log.isTraceEnabled())
this.log.trace("spanner: get(): {} -> {}", ByteUtil.toString(key), ByteUtil.toString(val));
return val;
} catch (SpannerException e) {
throw this.exceptionMapper != null ? this.exceptionMapper.apply(e) : e;
}
}
@Override
public KVPair getAtLeast(byte[] minKey, byte[] maxKey) {
if (this.log.isTraceEnabled()) {
this.log.trace("spanner: getAtLeast():\n minKey={}\n maxKey={}",
ByteUtil.toString(minKey), ByteUtil.toString(maxKey));
}
try (ResultSet resultSet = this.getPairs(minKey, maxKey, Options.limit(1))) {
return resultSet.next() ? ReadOnlySpannerView.kv(resultSet.getCurrentRowAsStruct()) : null;
} catch (SpannerException e) {
throw this.exceptionMapper != null ? this.exceptionMapper.apply(e) : e;
}
}
@Override
public KVPair getAtMost(byte[] maxKey, byte[] minKey) {
if (minKey != null && minKey.length == 0)
minKey = null;
try {
// After this bug is fixed: https://github.com/GoogleCloudPlatform/google-cloud-java/issues/1632
// try (ResultSet resultSet = this.getPairs(minKey, maxKey, Options.limit(1), Options.reverseOrder())) {
// return resultSet.next() ? ReadOnlySpannerView.kv(resultSet.getCurrentRowAsStruct()) : null;
final Statement.Builder builder = Statement.newBuilder("SELECT key, val FROM " + this.tableName);
this.addMaxKey(builder, maxKey, this.addMinKey(builder, minKey, false));
builder.append(" ORDER BY key DESC LIMIT 1");
if (this.log.isTraceEnabled()) {
this.log.trace("spanner: getAtMost():\n maxKey={}\n minKey={}\n query={}",
ByteUtil.toString(maxKey), ByteUtil.toString(minKey), builder.build());
}
try (ResultSet resultSet = this.context.executeQuery(builder.build())) {
return resultSet.next() ? ReadOnlySpannerView.kv(resultSet.getCurrentRowAsStruct()) : null;
}
} catch (SpannerException e) {
throw this.exceptionMapper != null ? this.exceptionMapper.apply(e) : e;
}
}
@Override
public CloseableIterator getRange(byte[] minKey, byte[] maxKey, boolean reverse) {
if (minKey != null && minKey.length == 0)
minKey = null;
try {
// After this bug is fixed: https://github.com/GoogleCloudPlatform/google-cloud-java/issues/1632
// return new Iter(this.getPairs(minKey, maxKey, Options.reverseOrder()));
if (!reverse)
return new Iter(this.getPairs(minKey, maxKey));
final Statement.Builder builder = Statement.newBuilder("SELECT key, val FROM " + this.tableName);
this.addMaxKey(builder, maxKey, this.addMinKey(builder, minKey, false));
builder.append(" ORDER BY key DESC");
if (this.log.isTraceEnabled()) {
this.log.trace("spanner: getRange():\n minKey={}\n maxKey={}\n reverse={}\n query={}",
ByteUtil.toString(minKey), ByteUtil.toString(maxKey), reverse, builder.build());
}
return new Iter(this.context.executeQuery(builder.build()));
} catch (SpannerException e) {
throw this.exceptionMapper != null ? this.exceptionMapper.apply(e) : e;
}
}
private ResultSet getPairs(byte[] minKey, byte[] maxKey, Options.ReadOption... options) {
final Key min = Key.of(ByteArray.copyFrom(minKey != null ? minKey : ByteUtil.EMPTY));
final Key max = maxKey != null ? Key.of(ByteArray.copyFrom(maxKey)) : TOP_KEY;
return this.context.read(this.tableName, KeySet.range(KeyRange.closedOpen(min, max)), KV_COL, options);
}
@Override
public void put(byte[] key, byte[] value) {
throw new UnsupportedOperationException("read-only view");
}
@Override
public void remove(byte[] key) {
throw new UnsupportedOperationException("read-only view");
}
@Override
public void removeRange(byte[] minKey, byte[] maxKey) {
throw new UnsupportedOperationException("read-only view");
}
// Closeable
/**
* {@linkplain ReadContext#close Closes} the associated {@link ReadContext}.
*/
@Override
public void close() {
try {
this.context.close();
} catch (Exception e) {
if (this.log.isDebugEnabled())
this.log.debug("got exception close of " + this.context + " (ignoring)", e);
}
}
// Internal methods
private boolean addMinKey(Statement.Builder builder, byte[] minKey, boolean where) {
return this.addKey(builder, minKey, "minKey", ">=", where);
}
private boolean addMaxKey(Statement.Builder builder, byte[] maxKey, boolean where) {
return this.addKey(builder, maxKey, "maxKey", "<", where);
}
private boolean addKey(Statement.Builder builder, byte[] key, String name, String op, boolean where) {
if (key == null)
return where;
builder.append(where ? " AND " : " WHERE ").append("key ").append(op).append(" @").append(name)
.bind(name).to(ByteArray.copyFrom(key));
return true;
}
protected static KVPair kv(Struct struct) {
Preconditions.checkArgument(struct != null);
return new KVPair(struct.getBytes(0).toByteArray(), struct.getBytes(1).toByteArray());
}
// Iter
private class Iter implements CloseableIterator {
private final ResultSet resultSet;
private Struct next;
Iter(ResultSet resultSet) {
this.resultSet = resultSet;
}
@Override
public boolean hasNext() {
try {
if (this.next != null)
return true;
if (!this.resultSet.next())
return false;
this.next = this.resultSet.getCurrentRowAsStruct();
return true;
} catch (SpannerException e) {
throw ReadOnlySpannerView.this.exceptionMapper != null ? ReadOnlySpannerView.this.exceptionMapper.apply(e) : e;
}
}
@Override
public KVPair next() {
if (this.next == null && !this.hasNext())
throw new NoSuchElementException();
final KVPair kv = ReadOnlySpannerView.kv(this.next);
this.next = null;
return kv;
}
@Override
public void remove() {
throw new UnsupportedOperationException("read-only view");
}
@Override
public void close() {
this.resultSet.close();
}
@Override
protected void finalize() throws Throwable {
try {
this.close();
} finally {
super.finalize();
}
}
}
}