This preface describes changes in Oracle Text for this release.
Changes in Oracle Text for Oracle Database Release 18c, Version 18.1
The changes in Oracle Text for Oracle Database release 18c, version 18.1 are described in this topic.
This section describes the primary new features for Oracle Text introduced in Oracle Database release 18c, version 18.1.
Faceted Navigation Support
Oracle Text provides faceted navigation support. You can now build applications with faceted navigation support by using
SDATA sections and Result Set Interface queries.
Support for Efficient Wildcard Search
Wildcard indexing supports fast and efficient wildcard search for all wildcard expressions. A new wordlist preference,
WILDCARD_INDEX, replaces the current options (
REVERSE_INDEX). When you enable
WILDCARD_INDEX, a K-gram (fixed-length substring particles) index indexes all substrings within each token. A new wordlist preference,
WILDCARD_INDEX_K, controls the length of grams used (that is, the length of each substring indexed).
Wildcard indexing is supported for languages which only use single-byte characters.
Automatic Background Index Maintenance
The query performance deteriorates when the
$G table is too fragmented. To avoid this, Oracle Text now provides automatic background optimize merge for every index or partition.
If the index synchronization has been running for some time, the index tables might get fragmented. To avoid this issue, Oracle Text now runs automatic background jobs to optimize the various index tables.
Oracle Text Reference for more information on
Oracle Text Reference for more information on
Support for Concurrent Data Manipulation Language Operations
Synchronization is performed as part of the same transaction for indexes created with the
SYNC (ON COMMIT) option. If there is a fatal index synchronization error, the entire data transaction is rolled back. Non-fatal (individual row) synchronization errors are logged in the
CTX_USER_INDEX_ERRORS view but the transaction still completes.
New Options to Optimize the Index
CTX_DDL.OPTIMIZE_INDEX procedure has two new parameters,
Support Indexing of JSON Key Names Longer Than 64 Characters
All Oracle Text index types, except
CTXRULE indexes, store tokens in a table column of type
VARCHAR2 (255 BYTE) now.
SDATA sections continue to store tokens in a table column of type
VARCHAR2 (249 BYTE).
You must rebuild any JSON search indexes and Oracle Text indexes created prior to Oracle Database 18c if they index JSON data that contains object fields with names longer than 64 bytes. See Oracle Database Upgrade Guide for more information.
Oracle Text Reference for more information about token limitations
The following features are deprecated in Oracle Database Release 18c, and may be desupported in a future release:
The deprecated features for Oracle Database Release 18c are described in Oracle Database Upgrade Guide.
Changes in Oracle Text 12c Release 2 (126.96.36.199)
The changes in Oracle Text for Oracle Database 12c Release 2 (188.8.131.52) are described in this topic.
This section describes the primary new features for Oracle Text introduced in Oracle Database 12c Release 2 (184.108.40.206).
SDATA Section Improvements
Oracle Text provides enhancements to the
SDATA section operations. A new kind of
SDATA section is added.
Keep Updated Documents in the Index
Oracle Text can keep updated index entries to search for original content with the
Oracle Text supports a new storage preference,
SMALL_R_ROW, for indexed lookups.
Oracle Text discontinued locked base table rows. A new
$U table for each index or partition keeps track of all concurrent updates and also introduces the new
$U_TABLE_CLAUSE storage clause for this
Reverse Token Index for Left-Truncated Queries
Oracle Text provides the new
REVERSE_INDEX attribute for left-truncated queries. This attribute is part of the wordlist preference and can be set to
FALSE. It is set to
FALSE by default so that the new feature is disabled. You can set this attribute with the
CTX_DDL.SET_ATTRIBUTE procedure. You can also add it with
ALTER INDEX REBUILD, just like any other wordlist preference. Use this attribute if you want better query performance for left-truncated queries.
Oracle Text Reference for more information about the
BASIC_WORDLIST attributes table and the
Partition-Specific Near Real-Time Indexes
Oracle Text supports the partition-specific
STAGE_ITAB option, which provides a two-level index mechanism to prevent the main index from fragmenting because of frequent inserts, updates, or deletes. Set this option at a partition level if, for example, partitions contain mostly static data, whereas other partitions contain rapidly changing data.
STAGE_ITAB_PARALLEL storage option controls the level of parallelism used to merge the data from the
$G staging table back into the
To prevent the near real-time
$G index table from becoming too large to fit into memory, specify a maximum size for the table.
Sentiment Analysis and Collocates
Oracle Text supports sentiment analysis and collocates. Sentiment analysis lets you identify positive and negative trends associated with search terms. Collocates let you identify other keywords that are related to, or used frequently with, a specified keyword.
NEAR2 Operator and NDATA Operator Enhancements
Oracle Text provides a new operator,
NEAR2, that is an enhanced version of the existing
NEAR operator. The
NEAR2 operator aims to combine the semantics of the
PHRASE, NEAR, and
NDATA operator now provides more control on the similarity scoring of character and phonetic matches. It also provides more control on the overall ranked results returned by the operation.
Join Character Support for Japanese VGRAM Lexer and WORLD Lexer
Oracle Text provides join character support for the Japanese
VGRAM lexer and
New Document Formats
Oracle Text provides new text filters to support new document formats.
Extract Synonyms of Words in Documents
Oracle Text provides new options in the
CTX_DOC package to enable thesaurus support. You can use the
CTX_DOC.POLICY_TOKENS procedures to extract synonyms of index tokens.
Read-only MDATA Sections
Oracle Text supports read-only
MDATA sections. When a section is queried, an extra cursor is not opened for each MDATA operator. Because you cannot add or remove MDATA values in a nonupdatable MDATA section, there is no extra overhead in tracking the updated MDATA values, and queries run faster.
Index Name Length and Long Identifier Support for Oracle Text Objects
Oracle Text index names can be as long as the database object names. The length is 128 bytes for Oracle Database release 12.2 compatible and later, and it is 30 bytes for earlier releases. Oracle Text supports long identifiers for Oracle Text objects. The maximum size was increased to 128 bytes.
Increased Default Value and Upper Limit of the MAX_INDEX_MEMORY Parameter
Oracle Text provides an increase in the default value and the upper limit of the
MAX_INDEX_MEMORY parameter that can be allocated for indexing purposes. The size was increased to 256 GB.
You can use a simpler alternative syntax to create a search index on JSON.
Oracle Database JSON Developer's Guide for more information about creating a search index for JSON