Package org.eclipse.jgit.lib

Class RefDatabase

java.lang.Object

org.eclipse.jgit.lib.RefDatabase

Direct Known Subclasses:

DfsRefDatabase, FileReftableDatabase, RefDirectory

public abstract class RefDatabase
extends Object

Abstraction of name to ObjectId mapping.

A reference database stores a mapping of reference names to ObjectId. Every Repository has a single reference database, mapping names to the tips of the object graph contained by the ObjectDatabase.

Field Summary

Fields

Modifier and Type	Field	Description
static String	ALL	Magic value for getRefsByPrefix(String) to return all references.
static int	MAX_SYMBOLIC_REF_DEPTH	Maximum number of times a SymbolicRef can be traversed.
protected static String[]	SEARCH_PATH	Order of prefixes to search when using non-absolute references.

Constructor Summary

Constructors

Constructor	Description
RefDatabase()

Method Summary

Modifier and Type	Method	Description
abstract void	close()	Close any resources held by this database.
abstract void	create()	Initialize a new reference database at this location.
abstract Ref	exactRef(String name)	Read a single reference.
Map<String,Ref>	exactRef(String... refs)	Read the specified references.
Ref	findRef(String name)	Read a single reference.
static Ref	findRef(Map<String,Ref> map, String name)	Try to find the specified name in the ref map using SEARCH_PATH.
Ref	firstExactRef(String... refs)	Find the first named reference.
abstract List<Ref>	getAdditionalRefs()	Get the additional reference-like entities from the repository.
Collection<String>	getConflictingNames(String name)	Determine if a proposed reference cannot coexist with existing ones.
Ref	getRef(String name)	Deprecated. Use findRef(String) instead.
List<Ref>	getRefs()	Returns all refs.
abstract Map<String,Ref>	getRefs(String prefix)	Deprecated. use getRefsByPrefix(java.lang.String) instead
List<Ref>	getRefsByPrefix(String prefix)	Returns refs whose names start with a given prefix.
List<Ref>	getRefsByPrefix(String... prefixes)	Returns refs whose names start with one of the given prefixes.
List<Ref>	getRefsByPrefixWithExclusions(String include, Set<String> excludes)	Returns refs whose names start with a given prefix excluding all refs that start with one of the given prefixes.
Set<Ref>	getTipsWithSha1(ObjectId id)	Returns all refs that resolve directly to the given ObjectId.
boolean	hasFastTipsWithSha1()	If the ref database does not support fast inverse queries, it may be advantageous to build a complete SHA1 to ref map in advance for multiple uses.
boolean	hasRefs()	Check if any refs exist in the ref database.
boolean	hasVersioning()	With versioning, each reference has a version number that increases on update.
abstract boolean	isNameConflicting(String name)	Determine if a proposed reference name overlaps with an existing one.
BatchRefUpdate	newBatchUpdate()	Create a new batch update to attempt on this database.
abstract RefRename	newRename(String fromName, String toName)	Create a new update command to rename a reference.
abstract RefUpdate	newUpdate(String name, boolean detach)	Create a new update command to create, modify or delete a reference.
abstract Ref	peel(Ref ref)	Peel a possibly unpeeled reference by traversing the annotated tags.
boolean	performsAtomicTransactions()	Whether the database is capable of performing batch updates as atomic transactions.
void	refresh()	Triggers a refresh of all internal data structures.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SEARCH_PATH

protected static final String[] SEARCH_PATH

Order of prefixes to search when using non-absolute references.

findRef(String) takes this search space into consideration when locating a reference by name. The first entry in the path is always "", ensuring that absolute references are resolved without further mangling.

MAX_SYMBOLIC_REF_DEPTH

public static final int MAX_SYMBOLIC_REF_DEPTH

Maximum number of times a SymbolicRef can be traversed.

If the reference is nested deeper than this depth, the implementation should either fail, or at least claim the reference does not exist.

Since:

4.2

See Also:

Constant Field Values

ALL

public static final String ALL

Magic value for getRefsByPrefix(String) to return all references.

See Also:

Constant Field Values

Constructor Detail

RefDatabase

public RefDatabase()

Method Detail

create

public abstract void create()
                     throws IOException

Initialize a new reference database at this location.

Throws:

IOException - the database could not be created.

close

public abstract void close()

Close any resources held by this database.

hasVersioning

public boolean hasVersioning()

With versioning, each reference has a version number that increases on update. See Ref.getUpdateIndex().

Returns:

true if the implementation assigns update indices to references.

Since:

5.3

isNameConflicting

public abstract boolean isNameConflicting(String name)
                                   throws IOException

Determine if a proposed reference name overlaps with an existing one.

Reference names use '/' as a component separator, and may be stored in a hierarchical storage such as a directory on the local filesystem.

If the reference "refs/heads/foo" exists then "refs/heads/foo/bar" must not exist, as a reference cannot have a value and also be a container for other references at the same time.

If the reference "refs/heads/foo/bar" exists than the reference "refs/heads/foo" cannot exist, for the same reason.

Parameters:

name - proposed name.

Returns:

true if the name overlaps with an existing reference; false if using this name right now would be safe.

Throws:

IOException - the database could not be read to check for conflicts.

See Also:

getConflictingNames(String)

getConflictingNames

@NonNull
public Collection<String> getConflictingNames(String name)
                                       throws IOException

Determine if a proposed reference cannot coexist with existing ones. If the passed name already exists, it's not considered a conflict.

Parameters:

name - proposed name to check for conflicts against

Returns:

a collection of full names of existing refs which would conflict with the passed ref name; empty collection when there are no conflicts

Throws:

IOException

Since:

2.3

See Also:

isNameConflicting(String)

newUpdate

@NonNull
public abstract RefUpdate newUpdate(String name,
                                    boolean detach)
                             throws IOException

Create a new update command to create, modify or delete a reference.

Parameters:

name - the name of the reference.

detach - if true and name is currently a SymbolicRef, the update will replace it with an ObjectIdRef. Otherwise, the update will recursively traverse SymbolicRefs and operate on the leaf ObjectIdRef.

Returns:

a new update for the requested name; never null.

Throws:

IOException - the reference space cannot be accessed.

newRename

@NonNull
public abstract RefRename newRename(String fromName,
                                    String toName)
                             throws IOException

Create a new update command to rename a reference.

Parameters:

fromName - name of reference to rename from

toName - name of reference to rename to

Returns:

an update command that knows how to rename a branch to another.

Throws:

IOException - the reference space cannot be accessed.

newBatchUpdate

@NonNull
public BatchRefUpdate newBatchUpdate()

Create a new batch update to attempt on this database.

The default implementation performs a sequential update of each command.

Returns:

a new batch update object.

performsAtomicTransactions

public boolean performsAtomicTransactions()

Whether the database is capable of performing batch updates as atomic transactions.

If true, by default BatchRefUpdate instances will perform updates atomically, meaning either all updates will succeed, or all updates will fail. It is still possible to turn off this behavior on a per-batch basis by calling update.setAtomic(false).

If false, BatchRefUpdate instances will never perform updates atomically, and calling update.setAtomic(true) will cause the entire batch to fail with REJECTED_OTHER_REASON.

This definition of atomicity is stronger than what is provided by ReceivePack. ReceivePack will attempt to reject all commands if it knows in advance some commands may fail, even if the storage layer does not support atomic transactions. Here, atomicity applies even in the case of unforeseeable errors.

Returns:

whether transactions are atomic by default.

Since:

3.6

getRef

@Deprecated
@Nullable
public final Ref getRef(String name)
                 throws IOException

Deprecated.

Use findRef(String) instead.

Compatibility synonym for findRef(String).

Parameters:

name - the name of the reference. May be a short name which must be searched for using the standard SEARCH_PATH.

Returns:

the reference (if it exists); else null.

Throws:

IOException - the reference space cannot be accessed.

findRef

@Nullable
public final Ref findRef(String name)
                  throws IOException

Read a single reference.

Aside from taking advantage of SEARCH_PATH, this method may be able to more quickly resolve a single reference name than obtaining the complete namespace by getRefs(ALL).get(name).

To read a specific reference without using @{link #SEARCH_PATH}, see exactRef(String).

Parameters:

name - the name of the reference. May be a short name which must be searched for using the standard SEARCH_PATH.

Returns:

the reference (if it exists); else null.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.3

exactRef

@Nullable
public abstract Ref exactRef(String name)
                      throws IOException

Read a single reference.

Unlike findRef(java.lang.String), this method expects an unshortened reference name and does not search using the standard SEARCH_PATH.

Parameters:

name - the unabbreviated name of the reference.

Returns:

the reference (if it exists); else null.

Throws:

IOException - the reference space cannot be accessed.

Since:

4.1

exactRef

@NonNull
public Map<String,Ref> exactRef(String... refs)
                               throws IOException

Read the specified references.

This method expects a list of unshortened reference names and returns a map from reference names to refs. Any named references that do not exist will not be included in the returned map.

Parameters:

refs - the unabbreviated names of references to look up.

Returns:

modifiable map describing any refs that exist among the ref ref names supplied. The map can be an unsorted map.

Throws:

IOException - the reference space cannot be accessed.

Since:

4.1

firstExactRef

@Nullable
public Ref firstExactRef(String... refs)
                  throws IOException

Find the first named reference.

This method expects a list of unshortened reference names and returns the first that exists.

Parameters:

refs - the unabbreviated names of references to look up.

Returns:

the first named reference that exists (if any); else null.

Throws:

IOException - the reference space cannot be accessed.

Since:

4.1

getRefs

@NonNull
public List<Ref> getRefs()
                  throws IOException

Returns all refs.

This includes HEAD, branches under ref/heads/, tags under refs/tags/, etc. It does not include pseudo-refs like FETCH_HEAD; for those, see getAdditionalRefs().

Symbolic references to a non-existent ref (for example, HEAD pointing to a branch yet to be born) are not included.

Callers interested in only a portion of the ref hierarchy can call getRefsByPrefix(java.lang.String) instead.

Returns:

immutable list of all refs.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.0

getRefs

@NonNull
@Deprecated
public abstract Map<String,Ref> getRefs(String prefix)
                                       throws IOException

Deprecated.

use getRefsByPrefix(java.lang.String) instead

Get a section of the reference namespace.

Parameters:

prefix - prefix to search the namespace with; must end with /. If the empty string (ALL), obtain a complete snapshot of all references.

Returns:

modifiable map that is a complete snapshot of the current reference namespace, with prefix removed from the start of each key. The map can be an unsorted map.

Throws:

IOException - the reference space cannot be accessed.

getRefsByPrefix

@NonNull
public List<Ref> getRefsByPrefix(String prefix)
                          throws IOException

Returns refs whose names start with a given prefix.

The default implementation uses getRefs(String). Implementors of RefDatabase should override this method directly if a better implementation is possible.

Parameters:

prefix - string that names of refs should start with; may be empty (to return all refs).

Returns:

immutable list of refs whose names start with prefix.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.0

getRefsByPrefixWithExclusions

@NonNull
public List<Ref> getRefsByPrefixWithExclusions(String include,
                                               Set<String> excludes)
                                        throws IOException

Returns refs whose names start with a given prefix excluding all refs that start with one of the given prefixes.

The default implementation is not efficient. Implementors of RefDatabase should override this method directly if a better implementation is possible.

Parameters:

include - string that names of refs should start with; may be empty.

excludes - strings that names of refs can't start with; may be empty.

Returns:

immutable list of refs whose names start with prefix and none of the strings in exclude.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.11

getRefsByPrefix

@NonNull
public List<Ref> getRefsByPrefix(String... prefixes)
                          throws IOException

Returns refs whose names start with one of the given prefixes.

The default implementation uses getRefsByPrefix(String). Implementors of RefDatabase should override this method directly if a better implementation is possible.

Parameters:

prefixes - strings that names of refs should start with.

Returns:

immutable list of refs whose names start with one of prefixes. Refs can be unsorted and may contain duplicates if the prefixes overlap.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.2

getTipsWithSha1

@NonNull
public Set<Ref> getTipsWithSha1(ObjectId id)
                         throws IOException

Returns all refs that resolve directly to the given ObjectId. Includes peeled ObjectIds. This is the inverse lookup of exactRef(String...).

The default implementation uses a linear scan. Implementors of RefDatabase should override this method directly if a better implementation is possible.

Parameters:

id - ObjectId to resolve

Returns:

a Set of Refs whose tips point to the provided id.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.4

hasFastTipsWithSha1

public boolean hasFastTipsWithSha1()
                            throws IOException

If the ref database does not support fast inverse queries, it may be advantageous to build a complete SHA1 to ref map in advance for multiple uses. To let applications decide on this decision, this function indicates whether the inverse map is available.

Returns:

whether this RefDatabase supports fast inverse ref queries.

Throws:

IOException - on I/O problems.

Since:

5.6

hasRefs

public boolean hasRefs()
                throws IOException

Check if any refs exist in the ref database.

This uses the same definition of refs as getRefs(). In particular, returns false in a new repository with no refs under refs/ and HEAD pointing to a branch yet to be born, and returns true in a repository with no refs under refs/ and a detached HEAD pointing to history.

Returns:

true if the database has refs.

Throws:

IOException - the reference space cannot be accessed.

Since:

5.0

getAdditionalRefs

@NonNull
public abstract List<Ref> getAdditionalRefs()
                                     throws IOException

Get the additional reference-like entities from the repository.

The result list includes non-ref items such as MERGE_HEAD and FETCH_RESULT cast to be refs. The names of these refs are not returned by getRefs() but are accepted by findRef(String) and exactRef(String).

Returns:

a list of additional refs

Throws:

IOException - the reference space cannot be accessed.

peel

@NonNull
public abstract Ref peel(Ref ref)
                  throws IOException

Peel a possibly unpeeled reference by traversing the annotated tags.

If the reference cannot be peeled (as it does not refer to an annotated tag) the peeled id stays null, but Ref.isPeeled() will be true.

Implementors should check Ref.isPeeled() before performing any additional work effort.

Parameters:

ref - The reference to peel

Returns:

ref if ref.isPeeled() is true; otherwise a new Ref object representing the same data as Ref, but isPeeled() will be true and getPeeledObjectId() will contain the peeled object (or null).

Throws:

IOException - the reference space or object space cannot be accessed.

refresh

public void refresh()

Triggers a refresh of all internal data structures.

In case the RefDatabase implementation has internal caches this method will trigger that all these caches are cleared.

Implementors should overwrite this method if they use any kind of caches.

findRef

@Nullable
public static Ref findRef(Map<String,Ref> map,
                          String name)

Try to find the specified name in the ref map using SEARCH_PATH.

Parameters:

map - map of refs to search within. Names should be fully qualified, e.g. "refs/heads/master".

name - short name of ref to find, e.g. "master" to find "refs/heads/master" in map.

Returns:

The first ref matching the name, or null if not found.

Since:

3.4