java.lang.Object | |
↳ | org.apache.lucene.index.IndexReader |
Known Direct Subclasses |
Known Indirect Subclasses |
IndexReader is an abstract class, providing an interface for accessing an index. Search of an index is done entirely through this abstract interface, so that any subclass which implements it is searchable.
Concrete subclasses of IndexReader are usually constructed with a call to
one of the static open()
methods, e.g. open(Directory, boolean)
.
For efficiency, in this API documents are often referred to via document numbers, non-negative integers which each name a unique document in the index. These document numbers are ephemeral--they may change as documents are added to and deleted from an index. Clients should thus not rely on a given document having the same number between sessions.
An IndexReader can be opened on a directory for which an IndexWriter is opened already, but it cannot be used to delete documents from the index then.
NOTE: for backwards API compatibility, several methods are not listed as abstract, but have no useful implementations in this base class and instead always throw UnsupportedOperationException. Subclasses are strongly encouraged to override these methods, but in many cases may not need to.
NOTE: as of 2.4, it's possible to open a read-only IndexReader using the static open methods that accept the boolean readOnly parameter. Such a reader has better concurrency as it's not necessary to synchronize on the isDeleted method. You must specify false if you want to make changes with the resulting IndexReader.
NOTE: IndexReader
instances are completely thread
safe, meaning multiple threads can call any of its methods,
concurrently. If your application requires external
synchronization, you should not synchronize on the
IndexReader
instance; use your own
(non-Lucene) objects instead.
Nested Classes | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
IndexReader.FieldOption | Constants describing field properties, for example used for
getFieldNames(FieldOption) . |
||||||||||
IndexReader.ReaderFinishedListener | A custom listener that's invoked when the IndexReader is finished. |
Fields | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
hasChanges | |||||||||||
readerFinishedListeners |
Protected Constructors | |||||||||||
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Public Methods | |||||||||||
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Expert: adds a
IndexReader.ReaderFinishedListener . | |||||||||||
Clones the IndexReader and optionally changes readOnly.
| |||||||||||
Efficiently clones the IndexReader (sharing most
internal state).
| |||||||||||
Closes files associated with this index.
| |||||||||||
Commit changes resulting from delete, undeleteAll, or
setNorm operations
If an exception is hit, then either no changes or all
changes will have been committed to the index
(transactional semantics).
| |||||||||||
Expert: decreases the refCount of this IndexReader
instance.
| |||||||||||
Deletes the document numbered
docNum . | |||||||||||
Deletes all documents that have a given
term indexed. | |||||||||||
Returns the directory associated with this index.
| |||||||||||
Returns the number of documents containing the term
t . | |||||||||||
Get the
Document at the n
th position. | |||||||||||
Returns the stored fields of the
n th
Document in this index. | |||||||||||
Retrieve the String userData optionally passed to
IndexWriter#commit.
| |||||||||||
Reads commitUserData, previously passed to
commit(Map) , from current index
segments file. | |||||||||||
Expert
| |||||||||||
Reads version number from segments files.
| |||||||||||
Expert.
| |||||||||||
Get a list of unique field names that exist in this index and have the specified
field option information.
| |||||||||||
Expert: return the IndexCommit that this reader has
opened.
| |||||||||||
Expert: returns the current refCount for this reader
| |||||||||||
Expert: returns the sequential sub readers that this
reader is logically composed of.
| |||||||||||
Load the Term Vector into a user-defined data structure instead of relying on the parallel arrays of
the
TermFreqVector . | |||||||||||
Return a term frequency vector for the specified document and field.
| |||||||||||
Map all the term vectors for all fields in a Document
| |||||||||||
Return an array of term frequency vectors for the specified document.
| |||||||||||
For IndexReader implementations that use
TermInfosReader to read terms, this returns the
current indexDivisor as specified when the reader was
opened.
| |||||||||||
Returns the number of unique terms (across all fields)
in this reader.
| |||||||||||
Version number when this IndexReader was opened.
| |||||||||||
Returns true if any documents have been deleted
| |||||||||||
Returns true if there are norms stored for this field.
| |||||||||||
Expert: increments the refCount of this IndexReader
instance.
| |||||||||||
Returns
true if an index exists at the specified directory. | |||||||||||
Check whether any new changes have occurred to the
index since this reader was opened.
| |||||||||||
Returns true if document n has been deleted
| |||||||||||
Checks is the index is optimized (if it has a single segment and
no deletions).
| |||||||||||
Returns the time the index in the named directory was last modified.
| |||||||||||
Returns all commit points that exist in the Directory.
| |||||||||||
Prints the filename and size of each file within a given compound file.
| |||||||||||
Returns one greater than the largest possible document number.
| |||||||||||
Reads the byte-encoded normalization factor for the named field of every
document.
| |||||||||||
Returns the byte-encoded normalization factor for the named field of
every document.
| |||||||||||
Returns the number of deleted documents.
| |||||||||||
Returns the number of documents in this index.
| |||||||||||
Returns an IndexReader reading the index in the given
Directory.
| |||||||||||
Expert: returns an IndexReader reading the index in the given
IndexCommit . | |||||||||||
Open a near real time IndexReader from the
IndexWriter . | |||||||||||
Expert: returns an IndexReader reading the index in
the given Directory, using a specific commit and with
a custom
IndexDeletionPolicy . | |||||||||||
Returns a IndexReader reading the index in the given
Directory, with readOnly=true.
| |||||||||||
Expert: returns an IndexReader reading the index in
the given Directory, with a custom
IndexDeletionPolicy . | |||||||||||
Expert: returns an IndexReader reading the index in
the given Directory, using a specific commit and with
a custom
IndexDeletionPolicy . | |||||||||||
Expert: returns an IndexReader reading the index in
the given Directory, with a custom
IndexDeletionPolicy . | |||||||||||
Expert: remove a previously added
IndexReader.ReaderFinishedListener . | |||||||||||
Expert: reopen this reader on a specific commit point.
| |||||||||||
Refreshes an IndexReader if the index has changed since this instance
was (re)opened.
| |||||||||||
Expert: returns a readonly reader, covering all
committed as well as un-committed changes to the index.
| |||||||||||
Just like
reopen() , except you can change the
readOnly of the original reader. | |||||||||||
This method is deprecated.
Use
setNorm(int, String, byte) instead, encoding the
float to byte with your Similarity's encodeNormValue(float) .
This method will be removed in Lucene 4.0
| |||||||||||
Expert: Resets the normalization factor for the named field of the named
document.
| |||||||||||
Returns an unpositioned
TermDocs enumerator. | |||||||||||
Returns an enumeration of all the documents which contain
term . | |||||||||||
Returns an enumeration of all the documents which contain
term . | |||||||||||
Returns an unpositioned
TermPositions enumerator. | |||||||||||
Returns an enumeration of all terms starting at a given term.
| |||||||||||
Returns an enumeration of all the terms in the index.
| |||||||||||
Undeletes all documents currently marked as deleted in
this index.
|
Protected Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Does nothing by default.
| |||||||||||
Commit changes resulting from delete, undeleteAll, or
setNorm operations
If an exception is hit, then either no changes or all
changes will have been committed to the index
(transactional semantics).
| |||||||||||
Implements close.
| |||||||||||
Implements commit.
| |||||||||||
Implements deletion of the document numbered
docNum . | |||||||||||
Implements setNorm in subclass.
| |||||||||||
Implements actual undeleteAll() in subclass.
| |||||||||||
[Expand]
Inherited Methods | |||||||||||
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From class
java.lang.Object
| |||||||||||
From interface
java.io.Closeable
|
Expert: adds a IndexReader.ReaderFinishedListener
. The
provided listener is also added to any sub-readers, if
this is a composite reader. Also, any reader reopened
or cloned from this one will also copy the listeners at
the time of reopen.
Clones the IndexReader and optionally changes readOnly. A readOnly reader cannot open a writeable reader.
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Efficiently clones the IndexReader (sharing most internal state).
On cloning a reader with pending changes (deletions, norms), the original reader transfers its write lock to the cloned reader. This means only the cloned reader may make further changes to the index, and commit the changes to the index on close, but the old reader still reflects all changes made up until it was cloned.
Like reopen()
, it's safe to make changes to
either the original or the cloned reader: all shared
mutable state obeys "copy on write" semantics to ensure
the changes are not seen by other readers.
Closes files associated with this index. Also saves any new deletions to disk. No other methods should be called after this has been called.
IOException | if there is a low-level IO error |
---|
Commit changes resulting from delete, undeleteAll, or setNorm operations If an exception is hit, then either no changes or all changes will have been committed to the index (transactional semantics).
IOException | if there is a low-level IO error |
---|
Expert: decreases the refCount of this IndexReader instance. If the refCount drops to 0, then pending changes (if any) are committed to the index and this reader is closed. If an exception is hit, the refCount is unchanged.
IOException | in case an IOException occurs in commit() or doClose() |
---|
Deletes the document numbered docNum
. Once a document is
deleted it will not appear in TermDocs or TermPostitions enumerations.
Attempts to read its field with the document(int)
method will result in an error. The presence of this document may still be
reflected in the docFreq(Term)
statistic, though
this will be corrected eventually as the index is further modified.
StaleReaderException | if the index has changed since this reader was opened |
---|---|
CorruptIndexException | if the index is corrupt |
LockObtainFailedException | if another writer
has this index open (write.lock could not
be obtained) |
IOException | if there is a low-level IO error |
Deletes all documents that have a given term
indexed.
This is useful if one uses a document field to hold a unique ID string for
the document. Then to delete such a document, one merely constructs a
term with the appropriate field and the unique ID string as its text and
passes it to this method.
See deleteDocument(int)
for information about when this deletion will
become effective.
StaleReaderException | if the index has changed since this reader was opened |
---|---|
CorruptIndexException | if the index is corrupt |
LockObtainFailedException | if another writer
has this index open (write.lock could not
be obtained) |
IOException | if there is a low-level IO error |
Returns the directory associated with this index. The Default implementation returns the directory specified by subclasses when delegating to the IndexReader(Directory) constructor, or throws an UnsupportedOperationException if one was not specified.
UnsupportedOperationException | if no directory |
---|
Returns the number of documents containing the term t
.
IOException | if there is a low-level IO error |
---|
Get the Document
at the n
th position. The FieldSelector
may be used to determine
what Field
s to load and how they should
be loaded. NOTE: If this Reader (more specifically, the underlying
FieldsReader
) is closed before the lazy
Field
is loaded an exception may be
thrown. If you want the value of a lazy
Field
to be available after closing you
must explicitly load it or fetch the Document again with a new loader.
NOTE: for performance reasons, this method does not check if the
requested document is deleted, and therefore asking for a deleted document
may yield unspecified results. Usually this is not required, however you
can call isDeleted(int)
with the requested document ID to verify
the document is not deleted.
n | Get the document at the n th position |
---|---|
fieldSelector | The FieldSelector to use to determine what
Fields should be loaded on the Document. May be null, in which case
all Fields will be loaded. |
Document
at the nth positionCorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Returns the stored fields of the n
th
Document
in this index.
NOTE: for performance reasons, this method does not check if the
requested document is deleted, and therefore asking for a deleted document
may yield unspecified results. Usually this is not required, however you
can call isDeleted(int)
with the requested document ID to verify
the document is not deleted.
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
commitUserData | Opaque Map (String -> String)
that's recorded into the segments file in the index,
and retrievable by getCommitUserData() . |
---|
IOException |
---|
Retrieve the String userData optionally passed to
IndexWriter#commit. This will return null if commit(Map)
has never been called for
this index.
Reads commitUserData, previously passed to commit(Map)
, from current index
segments file. This will return null if commit(Map)
has never been called for
this index.
directory | where the index resides. |
---|
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Reads version number from segments files. The version number is initialized with a timestamp and then increased by one for each change of the index.
directory | where the index resides. |
---|
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert. Warning: this returns null if the reader has no deletions
Get a list of unique field names that exist in this index and have the specified field option information.
fldOption | specifies which field option should be available for the returned fields |
---|
Expert: return the IndexCommit that this reader has opened. This method is only implemented by those readers that correspond to a Directory with its own segments_N file.
IOException |
---|
Expert: returns the current refCount for this reader
Expert: returns the sequential sub readers that this reader is logically composed of. For example, IndexSearcher uses this API to drive searching by one sub reader at a time. If this reader is not composed of sequential child readers, it should return null. If this method returns an empty array, that means this reader is a null reader (for example a MultiReader that has no sub readers).
NOTE: You should not try using sub-readers returned by
this method to make any changes (setNorm, deleteDocument,
etc.). While this might succeed for one composite reader
(like MultiReader), it will most likely lead to index
corruption for other readers (like DirectoryReader obtained
through open(IndexCommit, boolean)
. Use the parent reader directly.
Load the Term Vector into a user-defined data structure instead of relying on the parallel arrays of
the TermFreqVector
.
docNumber | The number of the document to load the vector for |
---|---|
field | The name of the field to load |
mapper | The TermVectorMapper to process the vector. Must not be null |
IOException | if term vectors cannot be accessed or if they do not exist on the field and doc. specified. |
---|
Return a term frequency vector for the specified document and field. The
returned vector contains terms and frequencies for the terms in
the specified field of this document, if the field had the storeTermVector
flag set. If termvectors had been stored with positions or offsets, a
TermPositionVector
is returned.
docNumber | document for which the term frequency vector is returned |
---|---|
field | field for which the term frequency vector is returned. |
IOException | if index cannot be accessed |
---|
Map all the term vectors for all fields in a Document
docNumber | The number of the document to load the vector for |
---|---|
mapper | The TermVectorMapper to process the vector. Must not be null |
IOException | if term vectors cannot be accessed or if they do not exist on the field and doc. specified. |
---|
Return an array of term frequency vectors for the specified document.
The array contains a vector for each vectorized field in the document.
Each vector contains terms and frequencies for all terms in a given vectorized field.
If no such fields existed, the method returns null. The term vectors that are
returned may either be of type TermFreqVector
or of type TermPositionVector
if
positions or offsets have been stored.
docNumber | document for which term frequency vectors are returned |
---|
IOException | if index cannot be accessed |
---|
For IndexReader implementations that use TermInfosReader to read terms, this returns the current indexDivisor as specified when the reader was opened.
Returns the number of unique terms (across all fields) in this reader. This method returns long, even though internally Lucene cannot handle more than 2^31 unique terms, for a possible future when this limitation is removed.
UnsupportedOperationException | if this count
cannot be easily determined (eg Multi*Readers).
Instead, you should call getSequentialSubReaders() and ask each sub reader for
its unique term count. |
---|---|
IOException |
Version number when this IndexReader was opened. Not implemented in the IndexReader base class.
If this reader is based on a Directory (ie, was
created by calling open(IndexCommit, boolean)
, or reopen()
on
a reader based on a Directory), then this method
returns the version recorded in the commit that the
reader opened. This version is advanced every time
commit()
is called.
If instead this reader is a near real-time reader
(ie, obtained by a call to getReader()
, or by calling reopen()
on a near real-time reader), then this method returns
the version of the last commit done by the writer.
Note that even as further changes are made with the
writer, the version will not changed until a commit is
completed. Thus, you should not rely on this method to
determine when a near real-time reader should be
opened. Use isCurrent()
instead.
UnsupportedOperationException | unless overridden in subclass |
---|
Returns true if any documents have been deleted
Returns true if there are norms stored for this field.
IOException |
---|
Expert: increments the refCount of this IndexReader
instance. RefCounts are used to determine when a
reader can be closed safely, i.e. as soon as there are
no more references. Be sure to always call a
corresponding decRef()
, in a finally clause;
otherwise the reader may never be closed. Note that
close()
simply calls decRef(), which means that
the IndexReader will not really be closed until decRef()
has been called for all outstanding
references.
Returns true
if an index exists at the specified directory.
directory | the directory to check for an index |
---|
true
if an index exists; false
otherwiseIOException | if there is a problem with accessing the index |
---|
Check whether any new changes have occurred to the index since this reader was opened.
If this reader is based on a Directory (ie, was
created by calling open(IndexCommit, boolean)
, or reopen()
on
a reader based on a Directory), then this method checks
if any further commits (see commit()
have occurred in that directory).
If instead this reader is a near real-time reader
(ie, obtained by a call to getReader()
, or by calling reopen()
on a near real-time reader), then this method checks if
either a new commmit has occurred, or any new
uncommitted changes have taken place via the writer.
Note that even if the writer has only performed
merging, this method will still return false.
In any event, if this returns false, you should call
reopen()
to get a new reader that sees the
changes.
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
UnsupportedOperationException | unless overridden in subclass |
Returns true if document n has been deleted
Checks is the index is optimized (if it has a single segment and no deletions). Not implemented in the IndexReader base class.
true
if the index is optimized; false
otherwiseUnsupportedOperationException | unless overridden in subclass |
---|
Returns the time the index in the named directory was last modified.
Do not use this to check whether the reader is still up-to-date, use
isCurrent()
instead.
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Returns all commit points that exist in the Directory.
Normally, because the default is KeepOnlyLastCommitDeletionPolicy
, there would be only
one commit point. But if you're using a custom IndexDeletionPolicy
then there could be many commits.
Once you have a given commit, you can open a reader on
it by calling open(IndexCommit, boolean)
There must be at least one commit in
the Directory, else this method throws IndexNotFoundException
. Note that if a commit is in
progress while this method is running, that commit
may or may not be returned.
IndexCommit
s, from oldest
to latest. IOException |
---|
Prints the filename and size of each file within a given compound file. Add the -extract flag to extract files to the current working directory. In order to make the extracted version of the index work, you have to copy the segments file from the compound index into the directory where the extracted files are stored.
args | Usage: org.apache.lucene.index.IndexReader [-extract] <cfsfile> |
---|
Returns one greater than the largest possible document number. This may be used to, e.g., determine how big to allocate an array which will have an element for every document number in an index.
Reads the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents.
IOException |
---|
Returns the byte-encoded normalization factor for the named field of every document. This is used by the search code to score documents. Returns null if norms were not indexed for this field.
IOException |
---|
Returns the number of deleted documents.
Returns the number of documents in this index.
Returns an IndexReader reading the index in the given Directory. You should pass readOnly=true, since it gives much better concurrent performance, unless you intend to do write operations (delete documents or change norms) with the reader.
directory | the index directory |
---|---|
readOnly | true if no changes (deletions, norms) will be made with this IndexReader |
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert: returns an IndexReader reading the index in the given
IndexCommit
. You should pass readOnly=true, since it
gives much better concurrent performance, unless you
intend to do write operations (delete documents or
change norms) with the reader.
commit | the commit point to open |
---|---|
readOnly | true if no changes (deletions, norms) will be made with this IndexReader |
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Open a near real time IndexReader from the IndexWriter
.
writer | The IndexWriter to open from |
---|---|
applyAllDeletes | If true, all buffered deletes will be applied (made visible) in the returned reader. If false, the deletes are not applied but remain buffered (in IndexWriter) so that they will be applied in the future. Applying deletes can be costly, so if your app can tolerate deleted documents being returned you might gain some performance by passing false. |
CorruptIndexException | |
IOException | if there is a low-level IO error |
CorruptIndexException |
Expert: returns an IndexReader reading the index in
the given Directory, using a specific commit and with
a custom IndexDeletionPolicy
. You should pass
readOnly=true, since it gives much better concurrent
performance, unless you intend to do write operations
(delete documents or change norms) with the reader.
commit | the specific IndexCommit to open;
see listCommits(Directory) to list all commits
in a directory |
---|---|
deletionPolicy | a custom deletion policy (only used
if you use this reader to perform deletes or to set
norms); see IndexWriter for details. |
readOnly | true if no changes (deletions, norms) will be made with this IndexReader |
termInfosIndexDivisor | Subsamples which indexed
terms are loaded into RAM. This has the same effect as setTermIndexInterval(int) except that setting
must be done at indexing time while this setting can be
set per reader. When set to N, then one in every
N*termIndexInterval terms in the index is loaded into
memory. By setting this to a value > 1 you can reduce
memory usage, at the expense of higher latency when
loading a TermInfo. The default value is 1. Set this
to -1 to skip loading the terms index entirely. This is only useful in
advanced situations when you will only .next() through all terms;
attempts to seek will hit an exception. |
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Returns a IndexReader reading the index in the given Directory, with readOnly=true.
directory | the index directory |
---|
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert: returns an IndexReader reading the index in
the given Directory, with a custom IndexDeletionPolicy
. You should pass readOnly=true,
since it gives much better concurrent performance,
unless you intend to do write operations (delete
documents or change norms) with the reader.
directory | the index directory |
---|---|
deletionPolicy | a custom deletion policy (only used
if you use this reader to perform deletes or to set
norms); see IndexWriter for details. |
readOnly | true if no changes (deletions, norms) will be made with this IndexReader |
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert: returns an IndexReader reading the index in
the given Directory, using a specific commit and with
a custom IndexDeletionPolicy
. You should pass
readOnly=true, since it gives much better concurrent
performance, unless you intend to do write operations
(delete documents or change norms) with the reader.
commit | the specific IndexCommit to open;
see listCommits(Directory) to list all commits
in a directory |
---|---|
deletionPolicy | a custom deletion policy (only used
if you use this reader to perform deletes or to set
norms); see IndexWriter for details. |
readOnly | true if no changes (deletions, norms) will be made with this IndexReader |
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert: returns an IndexReader reading the index in
the given Directory, with a custom IndexDeletionPolicy
. You should pass readOnly=true,
since it gives much better concurrent performance,
unless you intend to do write operations (delete
documents or change norms) with the reader.
directory | the index directory |
---|---|
deletionPolicy | a custom deletion policy (only used
if you use this reader to perform deletes or to set
norms); see IndexWriter for details. |
readOnly | true if no changes (deletions, norms) will be made with this IndexReader |
termInfosIndexDivisor | Subsamples which indexed
terms are loaded into RAM. This has the same effect as setTermIndexInterval(int) except that setting
must be done at indexing time while this setting can be
set per reader. When set to N, then one in every
N*termIndexInterval terms in the index is loaded into
memory. By setting this to a value > 1 you can reduce
memory usage, at the expense of higher latency when
loading a TermInfo. The default value is 1. Set this
to -1 to skip loading the terms index entirely. |
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert: remove a previously added IndexReader.ReaderFinishedListener
.
Expert: reopen this reader on a specific commit point. This always returns a readOnly reader. If the specified commit point matches what this reader is already on, and this reader is already readOnly, then this same instance is returned; if it is not already readOnly, a readOnly clone is returned.
CorruptIndexException | |
---|---|
IOException |
Refreshes an IndexReader if the index has changed since this instance was (re)opened.
Opening an IndexReader is an expensive operation. This method can be used to refresh an existing IndexReader to reduce these costs. This method tries to only load segments that have changed or were created after the IndexReader was (re)opened.
If the index has not changed since this instance was (re)opened, then this
call is a NOOP and returns this instance. Otherwise, a new instance is
returned. The old instance is not closed and remains usable.
If the reader is reopened, even though they share resources internally, it's safe to make changes (deletions, norms) with the new reader. All shared mutable state obeys "copy on write" semantics to ensure the changes are not seen by other readers.
You can determine whether a reader was actually reopened by comparing the old instance with the instance returned by this method:
IndexReader reader = ... ... IndexReader newReader = r.reopen(); if (newReader != reader) { ... // reader was reopened reader.close(); } reader = newReader; ...Be sure to synchronize that code so that other threads, if present, can never use reader after it has been closed and before it's switched to newReader.
NOTE: If this reader is a near real-time
reader (obtained from getReader()
,
reopen() will simply call writer.getReader() again for
you, though this may change in the future.
CorruptIndexException | if the index is corrupt |
---|---|
IOException | if there is a low-level IO error |
Expert: returns a readonly reader, covering all
committed as well as un-committed changes to the index.
This provides "near real-time" searching, in that
changes made during an IndexWriter session can be
quickly made available for searching without closing
the writer nor calling commit()
.
Note that this is functionally equivalent to calling
{#flush} (an internal IndexWriter operation) and then using open(IndexCommit, boolean)
to
open a new reader. But the turnaround time of this
method should be faster since it avoids the potentially
costly commit()
.
You must close the IndexReader
returned by
this method once you are done using it.
It's near real-time because there is no hard guarantee on how quickly you can get a new reader after making changes with IndexWriter. You'll have to experiment in your situation to determine if it's fast enough. As this is a new and experimental feature, please report back on your findings so we can learn, improve and iterate.
The resulting reader supports reopen()
, but that call will simply forward
back to this method (though this may change in the
future).
The very first time this method is called, this writer instance will make every effort to pool the readers that it opens for doing merges, applying deletes, etc. This means additional resources (RAM, file descriptors, CPU time) will be consumed.
For lower latency on reopening a reader, you should
call setMergedSegmentWarmer(IndexWriter.IndexReaderWarmer)
to
pre-warm a newly merged segment before it's committed
to the index. This is important for minimizing
index-to-search delay after a large merge.
If an addIndexes* call is running in another thread, then this reader will only search those segments from the foreign index that have been successfully copied over, so far
.NOTE: Once the writer is closed, any
outstanding readers may continue to be used. However,
if you attempt to reopen any of those readers, you'll
hit an AlreadyClosedException
.
writer | The IndexWriter to open from |
---|---|
applyAllDeletes | If true, all buffered deletes will be applied (made visible) in the returned reader. If false, the deletes are not applied but remain buffered (in IndexWriter) so that they will be applied in the future. Applying deletes can be costly, so if your app can tolerate deleted documents being returned you might gain some performance by passing false. |
IOException | |
CorruptIndexException | |
IOException |
Just like reopen()
, except you can change the
readOnly of the original reader. If the index is
unchanged but readOnly is different then a new reader
will be returned.
CorruptIndexException | |
---|---|
IOException |
This method is deprecated.
Use setNorm(int, String, byte)
instead, encoding the
float to byte with your Similarity's encodeNormValue(float)
.
This method will be removed in Lucene 4.0
Expert: Resets the normalization factor for the named field of the named document.
StaleReaderException | if the index has changed since this reader was opened |
---|---|
CorruptIndexException | if the index is corrupt |
LockObtainFailedException | if another writer
has this index open (write.lock could not
be obtained) |
IOException | if there is a low-level IO error |
Expert: Resets the normalization factor for the named field of the named
document. The norm represents the product of the field's boost
and its length normalization
. Thus, to preserve the length normalization
values when resetting this, one should base the new value upon the old.
NOTE: If this field does not store norms, then
this method call will silently do nothing.
StaleReaderException | if the index has changed since this reader was opened |
---|---|
CorruptIndexException | if the index is corrupt |
LockObtainFailedException | if another writer
has this index open (write.lock could not
be obtained) |
IOException | if there is a low-level IO error |
Returns an unpositioned TermDocs
enumerator.
Note: the TermDocs returned is unpositioned. Before using it, ensure
that you first position it with seek(Term)
or
seek(TermEnum)
.
IOException | if there is a low-level IO error |
---|
Returns an enumeration of all the documents which contain
term
. For each document, the document number, the frequency of
the term in that document is also provided, for use in
search scoring. If term is null, then all non-deleted
docs are returned with freq=1.
Thus, this method implements the mapping:
The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.
IOException | if there is a low-level IO error |
---|
Returns an enumeration of all the documents which contain
term
. For each document, in addition to the document number
and frequency of the term in that document, a list of all of the ordinal
positions of the term in the document is available. Thus, this method
implements the mapping:
This positional information facilitates phrase and proximity searching.
The enumeration is ordered by document number. Each document number is greater than all that precede it in the enumeration.
IOException | if there is a low-level IO error |
---|
Returns an unpositioned TermPositions
enumerator.
IOException | if there is a low-level IO error |
---|
Returns an enumeration of all terms starting at a given term. If the given term does not exist, the enumeration is positioned at the first term greater than the supplied term. The enumeration is ordered by Term.compareTo(). Each term is greater than all that precede it in the enumeration.
IOException | if there is a low-level IO error |
---|
Returns an enumeration of all the terms in the index. The
enumeration is ordered by Term.compareTo(). Each term is greater
than all that precede it in the enumeration. Note that after
calling terms(), next()
must be called
on the resulting enumeration before calling other methods such as
term()
.
IOException | if there is a low-level IO error |
---|
Undeletes all documents currently marked as deleted in this index.
NOTE: this method can only recover documents marked
for deletion but not yet removed from the index; when
and how Lucene removes deleted documents is an
implementation detail, subject to change from release
to release. However, you can use numDeletedDocs()
on the current IndexReader instance to
see how many documents will be un-deleted.
StaleReaderException | if the index has changed since this reader was opened |
---|---|
LockObtainFailedException | if another writer
has this index open (write.lock could not
be obtained) |
CorruptIndexException | if the index is corrupt |
IOException | if there is a low-level IO error |
Does nothing by default. Subclasses that require a write lock for index modifications must implement this method.
IOException |
---|
Commit changes resulting from delete, undeleteAll, or setNorm operations If an exception is hit, then either no changes or all changes will have been committed to the index (transactional semantics).
IOException | if there is a low-level IO error |
---|
Implements commit.
IOException |
---|
Implements deletion of the document numbered docNum
.
Applications should call deleteDocument(int)
or deleteDocuments(Term)
.
CorruptIndexException | |
---|---|
IOException |
Implements setNorm in subclass.
CorruptIndexException | |
---|---|
IOException |
Implements actual undeleteAll() in subclass.
CorruptIndexException | |
---|---|
IOException |