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lost_alien:
复杂的sql恐怕用这个就够呛了。。。。
DSL-SQL源码分析 -
liaobinxu:
shaopei3344 写道递归不是会引起栈溢出吗。说说递归在 ...
递归算法 -
shaopei3344:
递归不是会引起栈溢出吗。
说说递归在现实中的例子
递归算法
/**
* This class contains constants for configuration keys used
* in hdfs.
*
*/
@InterfaceAudience.Private
public class DFSConfigKeys extends CommonConfigurationKeys {
public static final String DFS_BLOCK_SIZE_KEY = "dfs.blocksize";
public static final long DFS_BLOCK_SIZE_DEFAULT = 64*1024*1024;
public static final String DFS_REPLICATION_KEY = "dfs.replication";
public static final short DFS_REPLICATION_DEFAULT = 3;
public static final String DFS_STREAM_BUFFER_SIZE_KEY = "dfs.stream-buffer-size";
public static final int DFS_STREAM_BUFFER_SIZE_DEFAULT = 4096;
public static final String DFS_BYTES_PER_CHECKSUM_KEY = "dfs.bytes-per-checksum";
public static final int DFS_BYTES_PER_CHECKSUM_DEFAULT = 512;
public static final String DFS_CLIENT_WRITE_PACKET_SIZE_KEY = "dfs.client-write-packet-size";
public static final int DFS_CLIENT_WRITE_PACKET_SIZE_DEFAULT = 64*1024;
public static final String DFS_NAMENODE_BACKUP_ADDRESS_KEY = "dfs.namenode.backup.address";
public static final String DFS_NAMENODE_BACKUP_ADDRESS_DEFAULT = "localhost:50100";
public static final String DFS_NAMENODE_BACKUP_HTTP_ADDRESS_KEY = "dfs.namenode.backup.http-address";
public static final String DFS_NAMENODE_BACKUP_HTTP_ADDRESS_DEFAULT = "0.0.0.0:50105";
public static final String DFS_DATANODE_BALANCE_BANDWIDTHPERSEC_KEY = "dfs.datanode.balance.bandwidthPerSec";
public static final long DFS_DATANODE_BALANCE_BANDWIDTHPERSEC_DEFAULT = 1024*1024;
public static final String DFS_NAMENODE_HTTP_ADDRESS_KEY = "dfs.namenode.http-address";
public static final String DFS_NAMENODE_HTTP_ADDRESS_DEFAULT = "0.0.0.0:50070";
public static final String DFS_NAMENODE_MAX_OBJECTS_KEY = "dfs.namenode.max.objects";
public static final long DFS_NAMENODE_MAX_OBJECTS_DEFAULT = 0;
public static final String DFS_NAMENODE_SAFEMODE_EXTENSION_KEY = "dfs.namenode.safemode.extension";
public static final int DFS_NAMENODE_SAFEMODE_EXTENSION_DEFAULT = 30000;
public static final String DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_KEY = "dfs.namenode.safemode.threshold-pct";
public static final float DFS_NAMENODE_SAFEMODE_THRESHOLD_PCT_DEFAULT = 0.999f;
public static final String DFS_NAMENODE_SECONDARY_HTTP_ADDRESS_KEY = "dfs.namenode.secondary.http-address";
public static final String DFS_NAMENODE_SECONDARY_HTTP_ADDRESS_DEFAULT = "0.0.0.0:50090";
public static final String DFS_NAMENODE_CHECKPOINT_PERIOD_KEY = "dfs.namenode.checkpoint.period";
public static final long DFS_NAMENODE_CHECKPOINT_PERIOD_DEFAULT = 3600;
public static final String DFS_NAMENODE_CHECKPOINT_SIZE_KEY = "dfs.namenode.checkpoint.size";
public static final long DFS_NAMENODE_CHECKPOINT_SIZE_DEFAULT = 4194304;
public static final String DFS_NAMENODE_UPGRADE_PERMISSION_KEY = "dfs.namenode.upgrade.permission";
public static final int DFS_NAMENODE_UPGRADE_PERMISSION_DEFAULT = 00777;
public static final String DFS_NAMENODE_HEARTBEAT_RECHECK_INTERVAL_KEY = "dfs.namenode.heartbeat.recheck-interval";
public static final int DFS_NAMENODE_HEARTBEAT_RECHECK_INTERVAL_DEFAULT = 5*60*1000;
public static final String DFS_CLIENT_HTTPS_KEYSTORE_RESOURCE_KEY = "dfs.client.https.keystore.resource";
public static final String DFS_CLIENT_HTTPS_KEYSTORE_RESOURCE_DEFAULT = "ssl-client.xml";
public static final String DFS_CLIENT_HTTPS_NEED_AUTH_KEY = "dfs.client.https.need-auth";
public static final boolean DFS_CLIENT_HTTPS_NEED_AUTH_DEFAULT = false;
public static final String DFS_NAMENODE_ACCESSTIME_PRECISION_KEY = "dfs.namenode.accesstime.precision";
public static final long DFS_NAMENODE_ACCESSTIME_PRECISION_DEFAULT = 3600000;
public static final String DFS_NAMENODE_REPLICATION_CONSIDERLOAD_KEY = "dfs.namenode.replication.considerLoad";
public static final boolean DFS_NAMENODE_REPLICATION_CONSIDERLOAD_DEFAULT = true;
public static final String DFS_NAMENODE_REPLICATION_INTERVAL_KEY = "dfs.namenode.replication.interval";
public static final int DFS_NAMENODE_REPLICATION_INTERVAL_DEFAULT = 3;
public static final String DFS_NAMENODE_REPLICATION_MIN_KEY = "dfs.namenode.replication.min";
public static final int DFS_NAMENODE_REPLICATION_MIN_DEFAULT = 1;
public static final String DFS_NAMENODE_REPLICATION_PENDING_TIMEOUT_SEC_KEY = "dfs.namenode.replication.pending.timeout-sec";
public static final int DFS_NAMENODE_REPLICATION_PENDING_TIMEOUT_SEC_DEFAULT = -1;
public static final String DFS_NAMENODE_REPLICATION_MAX_STREAMS_KEY = "dfs.namenode.replication.max-streams";
public static final int DFS_NAMENODE_REPLICATION_MAX_STREAMS_DEFAULT = 2;
public static final String DFS_PERMISSIONS_ENABLED_KEY = "dfs.permissions.enabled";
public static final boolean DFS_PERMISSIONS_ENABLED_DEFAULT = true;
public static final String DFS_PERMISSIONS_SUPERUSERGROUP_KEY = "dfs.permissions.superusergroup";
public static final String DFS_PERMISSIONS_SUPERUSERGROUP_DEFAULT = "supergroup";
public static final String DFS_SERVER_HTTPS_KEYSTORE_RESOURCE_KEY = "dfs.https.server.keystore.resource";
public static final String DFS_SERVER_HTTPS_KEYSTORE_RESOURCE_DEFAULT = "ssl-server.xml";
public static final String DFS_NAMENODE_NAME_DIR_RESTORE_KEY = "dfs.namenode.name.dir.restore";
public static final boolean DFS_NAMENODE_NAME_DIR_RESTORE_DEFAULT = false;
public static final String DFS_LIST_LIMIT = "dfs.ls.limit";
public static final int DFS_LIST_LIMIT_DEFAULT = 1000;
public static final String DFS_DATANODE_FAILED_VOLUMES_TOLERATED_KEY = "dfs.datanode.failed.volumes.tolerated";
public static final int DFS_DATANODE_FAILED_VOLUMES_TOLERATED_DEFAULT = 0;
//Delegation token related keys
public static final String DFS_NAMENODE_DELEGATION_KEY_UPDATE_INTERVAL_KEY = "dfs.namenode.delegation.key.update-interval";
public static final long DFS_NAMENODE_DELEGATION_KEY_UPDATE_INTERVAL_DEFAULT = 24*60*60*1000; // 1 day
public static final String DFS_NAMENODE_DELEGATION_TOKEN_RENEW_INTERVAL_KEY = "dfs.namenode.delegation.token.renew-interval";
public static final long DFS_NAMENODE_DELEGATION_TOKEN_RENEW_INTERVAL_DEFAULT = 24*60*60*1000; // 1 day
public static final String DFS_NAMENODE_DELEGATION_TOKEN_MAX_LIFETIME_KEY = "dfs.namenode.delegation.token.max-lifetime";
public static final long DFS_NAMENODE_DELEGATION_TOKEN_MAX_LIFETIME_DEFAULT = 7*24*60*60*1000; // 7 days
//Following keys have no defaults
public static final String DFS_DATANODE_DATA_DIR_KEY = "dfs.datanode.data.dir";
public static final String DFS_NAMENODE_HTTPS_ADDRESS_KEY = "dfs.namenode.https-address";
public static final String DFS_NAMENODE_HTTPS_ADDRESS_DEFAULT = "0.0.0.0:50470";
public static final String DFS_NAMENODE_NAME_DIR_KEY = "dfs.namenode.name.dir";
public static final String DFS_NAMENODE_EDITS_DIR_KEY = "dfs.namenode.edits.dir";
public static final String DFS_CLIENT_READ_PREFETCH_SIZE_KEY = "dfs.client.read.prefetch.size";
public static final String DFS_CLIENT_RETRY_WINDOW_BASE= "dfs.client.retry.window.base";
public static final String DFS_METRICS_SESSION_ID_KEY = "dfs.metrics.session-id";
public static final String DFS_DATANODE_HOST_NAME_KEY = "dfs.datanode.hostname";
public static final String DFS_DATANODE_STORAGEID_KEY = "dfs.datanode.StorageId";
public static final String DFS_NAMENODE_HOSTS_KEY = "dfs.namenode.hosts";
public static final String DFS_NAMENODE_HOSTS_EXCLUDE_KEY = "dfs.namenode.hosts.exclude";
public static final String DFS_CLIENT_SOCKET_TIMEOUT_KEY = "dfs.client.socket-timeout";
public static final String DFS_NAMENODE_CHECKPOINT_DIR_KEY = "dfs.namenode.checkpoint.dir";
public static final String DFS_NAMENODE_CHECKPOINT_EDITS_DIR_KEY = "dfs.namenode.checkpoint.edits.dir";
// Much code in hdfs is not yet updated to use these keys.
public static final String DFS_CLIENT_BLOCK_WRITE_LOCATEFOLLOWINGBLOCK_RETRIES_KEY = "dfs.client.block.write.locateFollowingBlock.retries";
public static final int DFS_CLIENT_BLOCK_WRITE_LOCATEFOLLOWINGBLOCK_RETRIES_DEFAULT = 5;
public static final String DFS_CLIENT_BLOCK_WRITE_RETRIES_KEY = "dfs.client.block.write.retries";
public static final int DFS_CLIENT_BLOCK_WRITE_RETRIES_DEFAULT = 3;
public static final String DFS_CLIENT_MAX_BLOCK_ACQUIRE_FAILURES_KEY = "dfs.client.max.block.acquire.failures";
public static final int DFS_CLIENT_MAX_BLOCK_ACQUIRE_FAILURES_DEFAULT = 3;
public static final String DFS_BALANCER_MOVEDWINWIDTH_KEY = "dfs.balancer.movedWinWidth";
public static final int DFS_BALANCER_MOVEDWINWIDTH_DEFAULT = 5400*1000;
public static final String DFS_DATANODE_ADDRESS_KEY = "dfs.datanode.address";
public static final String DFS_DATANODE_ADDRESS_DEFAULT = "0.0.0.0:50010";
public static final String DFS_DATANODE_DATA_DIR_PERMISSION_KEY = "dfs.datanode.data.dir.perm";
public static final String DFS_DATANODE_DATA_DIR_PERMISSION_DEFAULT = "755";
public static final String DFS_DATANODE_DIRECTORYSCAN_INTERVAL_KEY = "dfs.datanode.directoryscan.interval";
public static final int DFS_DATANODE_DIRECTORYSCAN_INTERVAL_DEFAULT = 21600;
public static final String DFS_DATANODE_DIRECTORYSCAN_THREADS_KEY = "dfs.datanode.directoryscan.threads";
public static final int DFS_DATANODE_DIRECTORYSCAN_THREADS_DEFAULT = 1;
public static final String DFS_DATANODE_DNS_INTERFACE_KEY = "dfs.datanode.dns.interface";
public static final String DFS_DATANODE_DNS_INTERFACE_DEFAULT = "default";
public static final String DFS_DATANODE_DNS_NAMESERVER_KEY = "dfs.datanode.dns.nameserver";
public static final String DFS_DATANODE_DNS_NAMESERVER_DEFAULT = "default";
public static final String DFS_DATANODE_DU_RESERVED_KEY = "dfs.datanode.du.reserved";
public static final long DFS_DATANODE_DU_RESERVED_DEFAULT = 0;
public static final String DFS_DATANODE_HANDLER_COUNT_KEY = "dfs.datanode.handler.count";
public static final int DFS_DATANODE_HANDLER_COUNT_DEFAULT = 3;
public static final String DFS_DATANODE_HTTP_ADDRESS_KEY = "dfs.datanode.http.address";
public static final String DFS_DATANODE_HTTP_ADDRESS_DEFAULT = "0.0.0.0:50075";
public static final String DFS_DATANODE_MAX_XCIEVERS_KEY = "dfs.datanode.max.xcievers";
public static final int DFS_DATANODE_MAX_XCIEVERS_DEFAULT = 256;
public static final String DFS_DATANODE_NUMBLOCKS_KEY = "dfs.datanode.numblocks";
public static final int DFS_DATANODE_NUMBLOCKS_DEFAULT = 64;
public static final String DFS_DATANODE_SCAN_PERIOD_HOURS_KEY = "dfs.datanode.scan.period.hours";
public static final int DFS_DATANODE_SCAN_PERIOD_HOURS_DEFAULT = 0;
public static final String DFS_DATANODE_SIMULATEDDATASTORAGE_KEY = "dfs.datanode.simulateddatastorage";
public static final boolean DFS_DATANODE_SIMULATEDDATASTORAGE_DEFAULT = false;
public static final String DFS_DATANODE_SIMULATEDDATASTORAGE_CAPACITY_KEY = "dfs.datanode.simulateddatastorage.capacity";
public static final long DFS_DATANODE_SIMULATEDDATASTORAGE_CAPACITY_DEFAULT = 2L<<40;
public static final String DFS_DATANODE_TRANSFERTO_ALLOWED_KEY = "dfs.datanode.transferTo.allowed";
public static final boolean DFS_DATANODE_TRANSFERTO_ALLOWED_DEFAULT = true;
public static final String DFS_HEARTBEAT_INTERVAL_KEY = "dfs.heartbeat.interval";
public static final long DFS_HEARTBEAT_INTERVAL_DEFAULT = 3;
public static final String DFS_NAMENODE_DECOMMISSION_INTERVAL_KEY = "dfs.namenode.decommission.interval";
public static final int DFS_NAMENODE_DECOMMISSION_INTERVAL_DEFAULT = 30;
public static final String DFS_NAMENODE_DECOMMISSION_NODES_PER_INTERVAL_KEY = "dfs.namenode.decommission.nodes.per.interval";
public static final int DFS_NAMENODE_DECOMMISSION_NODES_PER_INTERVAL_DEFAULT = 5;
public static final String DFS_NAMENODE_HANDLER_COUNT_KEY = "dfs.namenode.handler.count";
public static final int DFS_NAMENODE_HANDLER_COUNT_DEFAULT = 10;
public static final String DFS_SUPPORT_APPEND_KEY = "dfs.support.append";
public static final boolean DFS_SUPPORT_APPEND_DEFAULT = true;
public static final String DFS_HTTPS_ENABLE_KEY = "dfs.https.enable";
public static final boolean DFS_HTTPS_ENABLE_DEFAULT = false;
public static final String DFS_DEFAULT_CHUNK_VIEW_SIZE_KEY = "dfs.default.chunk.view.size";
public static final int DFS_DEFAULT_CHUNK_VIEW_SIZE_DEFAULT = 32*1024;
public static final String DFS_DATANODE_HTTPS_ADDRESS_KEY = "dfs.datanode.https.address";
public static final String DFS_DATANODE_HTTPS_ADDRESS_DEFAULT = "0.0.0.0:50475";
public static final String DFS_DATANODE_IPC_ADDRESS_KEY = "dfs.datanode.ipc.address";
public static final String DFS_DATANODE_IPC_ADDRESS_DEFAULT = "0.0.0.0:50020";
public static final String DFS_BLOCK_ACCESS_TOKEN_ENABLE_KEY = "dfs.block.access.token.enable";
public static final boolean DFS_BLOCK_ACCESS_TOKEN_ENABLE_DEFAULT = false;
public static final String DFS_BLOCK_ACCESS_KEY_UPDATE_INTERVAL_KEY = "dfs.block.access.key.update.interval";
public static final long DFS_BLOCK_ACCESS_KEY_UPDATE_INTERVAL_DEFAULT = 600L;
public static final String DFS_BLOCK_ACCESS_TOKEN_LIFETIME_KEY = "dfs.block.access.token.lifetime";
public static final long DFS_BLOCK_ACCESS_TOKEN_LIFETIME_DEFAULT = 600L;
public static final String DFS_REPLICATION_MAX_KEY = "dfs.replication.max";
public static final int DFS_REPLICATION_MAX_DEFAULT = 512;
public static final String DFS_DF_INTERVAL_KEY = "dfs.df.interval";
public static final int DFS_DF_INTERVAL_DEFAULT = 60000;
public static final String DFS_BLOCKREPORT_INTERVAL_MSEC_KEY = "dfs.blockreport.intervalMsec";
public static final long DFS_BLOCKREPORT_INTERVAL_MSEC_DEFAULT = 21600000;
public static final String DFS_BLOCKREPORT_INITIAL_DELAY_KEY = "dfs.blockreport.initialDelay";
public static final int DFS_BLOCKREPORT_INITIAL_DELAY_DEFAULT = 0;
//Keys with no defaults
public static final String DFS_DATANODE_PLUGINS_KEY = "dfs.datanode.plugins";
public static final String DFS_DATANODE_SOCKET_WRITE_TIMEOUT_KEY = "dfs.datanode.socket.write.timeout";
public static final String DFS_DATANODE_STARTUP_KEY = "dfs.datanode.startup";
public static final String DFS_NAMENODE_PLUGINS_KEY = "dfs.namenode.plugins";
public static final String DFS_WEB_UGI_KEY = "dfs.web.ugi";
public static final String DFS_NAMENODE_STARTUP_KEY = "dfs.namenode.startup";
public static final String DFS_DATANODE_KEYTAB_FILE_KEY = "dfs.datanode.keytab.file";
public static final String DFS_DATANODE_USER_NAME_KEY = "dfs.datanode.user.name.key";
public static final String DFS_NAMENODE_KEYTAB_FILE_KEY = "dfs.namenode.keytab.file";
public static final String DFS_NAMENODE_USER_NAME_KEY = "dfs.namenode.user.name.key";
}
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