Todo
From PostgreSQL wiki
This list contains known PostgreSQL bugs and feature requests and we hope it is complete. If you would like to work on an item, please read the Developer FAQ first. There is also a development information page.
-
- marks ordinary, incomplete items
- [E] - marks items that are easier to implement
- [D]
- marks changes that are done, and will appear in the PostgreSQL 9.5 release.
For help on editing this list, please see Talk:Todo. Please do not add items here without discussion on the mailing list.
Development Process
WARNING for Developers: Unfortunately this list does not contain all the information necessary for someone to start coding a feature. Some of these items might have become unnecessary since they were added --- others might be desirable but the implementation might be unclear. When selecting items listed below, be prepared to first discuss the value of the feature. Do not assume that you can select one, code it and then expect it to be committed. Always discuss design on Hackers list before starting to code. The flow should be:
Desirability -> Design -> Implement -> Test -> Review -> Commit
Administration
- Allow administrators to cancel multi-statement idle transactions
- This allows locks to be released, but it is complex to report the cancellation back to the client.
- Allow administrators to cancel long-lived prepared transactions
- Check for unreferenced table files created by transactions that were in-progress when the server terminated abruptly
- Set proper permissions on non-system schemas during db creation
- Currently all schemas are owned by the super-user because they are copied from the template1 database. However, since all objects are inherited from the template database, it is not clear that setting schemas to the db owner is correct.
- Allow log_min_messages to be specified on a per-module basis
- This would allow administrators to see more detailed information from specific sections of the backend, e.g. checkpoints, autovacuum, etc. Another idea is to allow separate configuration files for each module, or allow arbitrary SET commands to be passed to them. See also Logging Brainstorm.
- Simplify creation of partitioned tables
- This would allow creation of partitioned tables without requiring creation of triggers or rules for INSERT/UPDATE/DELETE, and constraints for rapid partition selection. Options could include range and hash partition selection. See also Table partitioning
- Allow custom variables to appear in pg_settings()
- Have custom variables be transaction-safe
- Implement the SQL-standard mechanism whereby REVOKE ROLE revokes only the privilege granted by the invoking role, and not those granted by other roles
- Prevent query cancel packets from being replayed by an attacker, especially when using SSL
- Provide a way to query the log collector subprocess to determine the name of the currently active log file
- Allow simpler reporting of the unix domain socket directory and allow easier configuration of its default location
- Improve logging of prepared transactions recovered during startup
- Allow logging of replication and SPI/function-internal queries
- Consider supporting incremental base backups
Configuration files
- Consider normalizing fractions in postgresql.conf, perhaps using '%'
- Allow Kerberos to disable stripping of realms so we can check the username@realm against multiple realms
- Improve LDAP authentication configuration options
- Add external tool to auto-tune some postgresql.conf parameters
- Add 'hostgss' pg_hba.conf option to allow GSS link-level encryption
- Process pg_hba.conf keywords as case-insensitive
- Allow pg_hba.conf to process include files
- Create utility to compute accurate random_page_cost value
- Allow synchronous_standby_names to be disabled after communication failure with all synchronous standby servers exceeds some timeout
- This also requires successful execution of a synchronous notification command.
- Fix log_line_prefix to display the transaction id (%x) for statements not in a transaction block
- Currently it displays zero.
- [E] If pg_hba.conf has changed since last config reload and we reject an authentication attempt, emit a HINT to the user and in the log
- Adjust rounding behavior for numeric GUC values
- Develop replacement for MD5 authentication
Tablespaces
- Allow a database in tablespace t1 with tables created in tablespace t2 to be used as a template for a new database created with default tablespace t2
- Currently all objects in the default database tablespace must have default tablespace specifications. This is because new databases are created by copying directories. If you mix default tablespace tables and tablespace-specified tables in the same directory, creating a new database from such a mixed directory would create a new database with tables that had incorrect explicit tablespaces. To fix this would require modifying pg_class in the newly copied database, which we don't currently do.
- Allow reporting of which objects are in which tablespaces
- This item is difficult because a tablespace can contain objects from multiple databases. There is a server-side function that returns the databases which use a specific tablespace, so this requires a tool that will call that function and connect to each database to find the objects in each database for that tablespace.
- Allow WAL replay of CREATE TABLESPACE to work when the directory structure on the recovery computer is different from the original
- Allow per-tablespace quotas
- Allow tablespaces on RAM-based partitions for unlogged tables
- Allow toast tables to be moved to a different tablespace
- Close race in DROP TABLESPACE on Windows
- Add per-tablespace effective_io_concurrency
Statistics Collector
- Allow statistics last vacuum/analyze execution times to be displayed without requiring track_counts to be enabled
- [D] Clear table counters on TRUNCATE
- Testing pgstat via pg_regress is tricky and inefficient. Consider making a dedicated pgstat test-suite.
- Track number of WAL files ready to be archived in pg_stat_archiver
SSL
- Allow SSL authentication/encryption over unix domain sockets
- Allow SSL key file permission checks to be optionally disabled when sharing SSL keys with other applications
- Allow SSL CRL files to be re-read during configuration file reload, rather than requiring a server restart
-
Unlike SSL CRT files, CRL (Certificate Revocation List) files are updated frequently
Alternatively or additionally supporting OCSP (online certificate security protocol) would provide real-time revocation discovery without reloading
- Allow automatic selection of SSL client certificates from a certificate store
- Send the full certificate server chain to the client
- Re-read SSL certificates on server reload
Point-In-Time Recovery (PITR)
- Allow archive_mode to be changed without server restart?
- Consider avoiding WAL switching via archive_timeout if there has been no database activity
- Allow base backup from standby to continue when the standby is promoted.
Standby server mode
- Allow pg_xlogfile_name() to be used in recovery mode
- Prevent variables inherited from the server environment from begin used for making streaming replication connections.
- Change walsender so that it applies per-role settings
- Restructure configuration parameters for standby mode
- Add a new "eager" synchronous mode that starts out synchronous but reverts to asynchronous after a failure timeout period
- This would require some type of command to be executed to alert administrators of this change.
Data Types
- Fix data types where equality comparison is not intuitive, e.g. box
- Add support for public SYNONYMs
- Add support for SQL-standard GENERATED/IDENTITY columns
- Consider placing all sequences in a single table, or create a system view
- Consider a special data type for regular expressions
- Allow renaming and deleting enumerated values from an existing enumerated data type
- Support scoped IPv6 addresses in the inet type
- Considering improving performance of computing CHAR() value lengths
- Add overlaps geometric operators that ignore point overlaps
- Remove or improve rounding in geometric comparison operators
- Add IMMUTABLE column attribute
Domains
- Allow functions defined as casts to domains to be called during casting
- Allow values to be cast to domain types
- Make domains work better with polymorphic functions
Dates and Times
- Allow infinite intervals just like infinite timestamps
- Determine how to represent date/time field extraction on infinite timestamps
- Allow TIMESTAMP WITH TIME ZONE to store the original timezone information, either zone name or offset from UTC
- If the TIMESTAMP value is stored with a time zone name, interval computations should adjust based on the time zone rules.
- Have timestamp subtraction not call justify_hours()?
- Add function to allow the creation of timestamps using parameters
- Allow a comma to denote fractional seconds in ISO-8601-compliant times (and timestamps)
Arrays
- Add support for arrays of domains
- Allow single-byte header storage for array elements
- Add function to detect if an array is empty
- Improve handling of NULLs in arrays
Binary Data
- Improve vacuum of large objects, like contrib/vacuumlo?
- Auto-delete large objects when referencing row is deleted
- contrib/lo offers this functionality.
- Allow read/write into TOAST values like large objects
- Writing might require the TOAST column to be stored EXTERNAL.
MONEY Data Type
- Add locale-aware MONEY type, and support multiple currencies
- MONEY dumps in a locale-specific format making it difficult to restore to a system with a different locale
Text Search
- Allow dictionaries to change the token that is passed on to later dictionaries
- Exact phrase search,
- Consider a function-based API for '@@' searches
- Improve text search error messages
- Consider changing error to warning for strings larger than one megabyte
- tsearch and tsdicts regression tests fail in Turkish locale on glibc
- tsquery negator operator treated as part of lexeme
- Improve handling of dash and plus signs in email address user names, and perhaps improve URL parsing
- Improve default parser, to more easily allow adding new tokens
- Add additional support functions
XML
- Allow XML arrays to be cast to other data types
- Add XML Schema validation and xmlvalidate functions (SQL:2008)
- Add xmlvalidatedtd variant to support validating against a DTD?
- Relax-NG validation; libxml2 supports this already
- Allow reliable XML operation non-UTF8 server encodings (xpath(), in particular, is known to not work)
- Add functions from SQL:2006: XMLDOCUMENT, XMLCAST, XMLTEXT
- Add XMLNAMESPACES support in XMLELEMENT and elsewhere
- Move XSLT from contrib/xml2 to a more reasonable location
- Report errors returned by the XSLT library
- Improve the XSLT parameter passing API
- XML Canonical: Convert XML documents to canonical form to compare them. libxml2 has support for this.
- Add pretty-printed XML output option
- Parse a document and serialize it back in some indented form. libxml2 might support this.
- Add XMLQUERY (from the SQL/XML standard)
- Allow XML shredding
- In some cases shredding could be better option (if there is no need to keep XML docs entirely, e.g. if we have already developed tools that understand only relational data. This would be a separate module that implements annotated schema decomposition technique, similar to DB2 and SQL Server functionality.
- xpath_table needs to be implemented/implementable to get rid of contrib/xml2 [10]
- xpath_table is pretty broken anyway [11]
- Improve handling of PIs and DTDs in xmlconcat() [14]
- Restructure XML and /contrib/xml2 functionality
- Verify Xpath escaping behavior
Functions
- Enforce typmod for function inputs, function results and parameters for spi_prepare'd statements called from PLs
- Fix IS OF so it matches the ISO specification, and add documentation
- Implement Boyer-Moore searching in LIKE queries
- Prevent malicious functions from being executed with the permissions of unsuspecting users
- Index functions are safe, so VACUUM and ANALYZE are safe too. Triggers, CHECK and DEFAULT expressions, and rules are still vulnerable.
- Reduce memory usage of aggregates in set returning functions
- Fix /contrib/ltree operator
- Fix /contrib/btree_gist's implementation of inet indexing
- Fix inconsistent precedence of =, >, and < compared to <>, >=, and <=
- Fix regular expression bug when using complex back-references
- Have /contrib/dblink reuse unnamed connections
- Improve formatting of pg_get_viewdef() output
- Add function to dump pg_depend information cleanly
- Add function to allow easier transaction id comparisons
- [D] Add generate_series(numeric, numeric)
- [E] Add an ereport wrapper callable from SQL. Note that you'll need to use the anyelement hack to deal with the need for a return type, e.g. ereport(text, anyelement) returns anyelement.
- [E] Add a hex option to decode(...) and encode(...), so you can encode/decode hex strings
- [D] Add a built-in array_agg(anyarray) or similar, that can aggregate 1-dimensional arrays into a 2-dimensional array.
- [E] Add a built-in array_cat_agg (naming to be bikeshedded) that concatenates input 1-dim arrays into a single long 1-dim array
Character Formatting
- Allow to_date() and to_timestamp() to accept localized month names
- Add missing parameter handling in to_char()
- Throw an error from to_char() instead of printing a string of "#" when a number doesn't fit in the desired output format.
- discussed in "to_char, support for EEEE format"
- Allow to_char() on interval values to accumulate the highest unit requested
-
Some special format flag would be required to request such accumulation. Such functionality could also be added to EXTRACT. Prevent accumulation that crosses the month/day boundary because of the uneven number of days in a month.
- to_char(INTERVAL '1 hour 5 minutes', 'MI') => 65
- to_char(INTERVAL '43 hours 20 minutes', 'MI' ) => 2600
- to_char(INTERVAL '43 hours 20 minutes', 'WK:DD:HR:MI') => 0:1:19:20
- to_char(INTERVAL '3 years 5 months','MM') => 41
- Fix to_number() handling for values not matching the format string
Multi-Language Support
- Add NCHAR (as distinguished from ordinary varchar)
- Add a cares-about-collation column to pg_proc, so that unresolved-collation errors can be thrown at parse time
- Integrate collations with text search configurations
- Integrate collations with to_char() and related functions
- Support collation-sensitive equality and hashing functions
- Add a LOCALE option to CREATE DATABASE, as a shorthand
- Support multiple simultaneous character sets, per SQL:2008
- Improve UTF8 combined character handling?
- Add octet_length_server() and octet_length_client()
- Make octet_length_client() the same as octet_length()?
- Fix problems with wrong runtime encoding conversion for NLS message files
- Add URL to more complete multi-byte regression tests
- Fix contrib/fuzzystrmatch to work with multibyte encodings
- Change memory allocation for multi-byte functions so memory is allocated inside conversion functions
- Currently we preallocate memory based on worst-case usage.
- Add ability to use case-insensitive regular expressions on multi-byte characters
- Currently it works for UTF-8, but not other multi-byte encodings
- Improve encoding of connection startup messages sent to the client
- Currently some authentication error messages are sent in the server encoding
- More sensible support for Unicode combining characters, normal forms
- Detect operating system collation changes, or make Postgres immune to them
Views and Rules
- Allow VIEW/RULE recompilation when the underlying tables change
- This is both difficult and controversial.
- Make it possible to use RETURNING together with conditional DO INSTEAD rules, such as for partitioning setups
- Improve ability to modify views via ALTER TABLE
SQL Commands
- Add CORRESPONDING BY to UNION/INTERSECT/EXCEPT
- Improve type determination of unknown (NULL or quoted literal) result columns for UNION/INTERSECT/EXCEPT
- Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
- Allow prepared transactions with temporary tables created and dropped in the same transaction, and when an ON COMMIT DELETE ROWS temporary table is accessed
- Add a GUC variable to warn about non-standard SQL usage in queries
- Add SQL-standard MERGE/REPLACE/UPSERT command
- MERGE is typically used to merge two tables. An UPSERT command does an INSERT, or in the event of a would-be duplicate violation, an UPDATE. See UPSERT for notes on the implementation details.
- Add NOVICE output level for helpful messages
- For example, have it warn about unjoined tables. This could also control automatic sequence/index creation messages.
- Allow NOTIFY in rules involving conditionals
- Allow LISTEN on patterns
- Allow EXPLAIN to identify tables that were skipped because of constraint_exclusion
- Simplify dropping roles that have objects in several databases
- Allow the count returned by SELECT, etc to be represented as an int64 to allow a higher range of values
- Add support for WITH RECURSIVE ... CYCLE
- Add DEFAULT .. AS OWNER so permission checks are done as the table owner
- This would be useful for SERIAL nextval() calls and CHECK constraints.
- Allow DISTINCT to work in multiple-argument aggregate calls
- Add comments on system tables/columns using the information in catalogs.sgml
- Ideally the information would be pulled from the SGML file automatically.
- Prevent the specification of conflicting transaction read/write options
- Allow DELETE and UPDATE to be used with LIMIT and ORDER BY
- Allow PREPARE of cursors
- Have DISCARD PLANS discard plans cached by functions
- DISCARD all should do the same.
- Avoid multiple-evaluation of BETWEEN and IN arguments containing volatile expressions
- Fix nested CASE-WHEN constructs
- IS NULL testing of nested ROW() values is inconsistent
- Allow: COPY ( EXECUTE prepare_label [(...)] ) TO 'local_file.out'
- "query" is defined to accept only SELECT and VALUES but EXECUTE has merit as well.
- Consider, in psql, an idiom of: PREPARE long_query AS SELECT [...]; \copy (EXECUTE long_query) TO ...
CREATE
- Allow CREATE TABLE AS to determine column lengths for complex expressions like SELECT col1
- Have WITH CONSTRAINTS also create constraint indexes
- Move NOT NULL constraint information to pg_constraint
- Currently NOT NULL constraints are stored in pg_attribute without any designation of their origins, e.g. primary keys. One manifest problem is that dropping a PRIMARY KEY constraint does not remove the NOT NULL constraint designation. Another issue is that we should probably force NOT NULL to be propagated from parent tables to children, just as CHECK constraints are. (But then does dropping PRIMARY KEY affect children?)
- Prevent concurrent CREATE TABLE from sometimes returning a cryptic error message
- Add CREATE SCHEMA ... LIKE that copies a schema
- Fix CREATE OR REPLACE FUNCTION to not leave objects depending on the function in inconsistent state
- Allow temporary tables to exist as empty by default in all sessions
- Allow the creation of "distinct" types
- Consider analyzing temporary tables when they are first used in a query
- Autovacuum cannot analyze or vacuum temporary tables.
- [D] Allow an unlogged table to be changed to logged
UPDATE
- Allow UPDATE tab SET ROW (col, ...) = (SELECT...)
- Research self-referential UPDATEs that see inconsistent row versions in read-committed mode
- Improve performance of EvalPlanQual mechanism that rechecks already-updated rows
- This is related to the previous item, which questions whether it even has the right semantics
ALTER
- Have ALTER TABLE RENAME of a SERIAL column rename the sequence
- Have ALTER SEQUENCE RENAME rename the sequence name stored in the sequence table
- Add ALTER DOMAIN to modify the underlying data type
- Allow ALTER TABLESPACE to move the tablespace to different directories
- Allow moving system tables to other tablespaces, where possible
- Currently non-global system tables must be in the default database tablespace. Global system tables can never be moved.
- Have ALTER INDEX update the name of a constraint using that index
- Allow column display reordering by recording a display, storage, and permanent id for every column?
- Allow deactivating (and reactivating) indexes via ALTER TABLE
- Add ALTER OPERATOR ... RENAME
- needs to consider effects of changing operator precedence
CLUSTER
- Automatically maintain clustering on a table
- This might require some background daemon to maintain clustering during periods of low usage. It might also require tables to be only partially filled for easier reorganization. Another idea would be to create a merged heap/index data file so an index lookup would automatically access the heap data too. A third idea would be to store heap rows in hashed groups, perhaps using a user-supplied hash function.
- Allow CLUSTER to be used on a partial index
COPY
- Allow COPY to report error lines and continue
- This requires the use of a savepoint before each COPY line is processed, with ROLLBACK on COPY failure.
- Allow COPY FROM to create index entries in bulk
- Improve COPY performance
- Allow COPY to report errors sooner
- Allow COPY to handle other number formats
- E.g. the German notation. Best would be something like WITH DECIMAL ','.
- Allow a stalled COPY to exit if the backend is terminated
- Allow COPY "text" format to output a header
GRANT/REVOKE
- Allow SERIAL sequences to inherit permissions from the base table?
- Allow dropping of a role that has connection rights
DECLARE CURSOR
- Prevent DROP TABLE from dropping a table referenced by its own open cursor?
- Provide some guarantees about the behavior of cursors that invoke volatile functions
INSERT
- Allow INSERT/UPDATE of the system-generated oid value for a row
SHOW/SET
- Add SET PERFORMANCE_TIPS option to suggest INDEX, VACUUM, VACUUM ANALYZE, and CLUSTER
- Rationalize the discrepancy between settings that use values in bytes and SHOW that returns the object count
ANALYZE
- Have EXPLAIN ANALYZE issue NOTICE messages when the estimated and actual row counts differ by a specified percentage
- Have EXPLAIN ANALYZE report rows as floating-point numbers
- Improve how ANALYZE computes in-doubt tuples
Window Functions
See TODO items for window functions.
- Support creation of user-defined window functions
- We have the ability to create new window functions written in C. Is it worth the effort to create an API that would let them be written in PL/pgsql, etc?
- Implement full support for window framing clauses
-
In addition to done clauses described in the latest doc, these clauses are not implemented yet.
- RANGE BETWEEN ... PRECEDING/FOLLOWING
- EXCLUDE
- Investigate tuplestore performance issues
- The tuplestore_in_memory() thing is just a band-aid, we ought to try to solve it properly. tuplestore_advance seems like a weak spot as well.
- Do we really need so much duplicated code between Agg and WindowAgg?
- Teach planner to evaluate multiple windows in the optimal order
- Currently windows are always evaluated in the query-specified order.
- Implement DISTINCT clause in window aggregates
- Some proprietary RDBMSs have implemented it already, so it helps with porting from those.
Integrity Constraints
Keys
- Improve deferrable unique constraints for cases with many conflicts
- The current implementation fires a trigger for each potentially conflicting row. This might not scale well for an update that changes many key values at once.
Referential Integrity
- Add MATCH PARTIAL referential integrity
- Change foreign key constraint for array -> element to mean element in array?
- Fix problem when cascading referential triggers make changes on cascaded tables, seeing the tables in an intermediate state
- Are ri_KeysEqual checks in the RI enforcement triggers still necessary?
Check Constraints
- Run check constraints only when affected columns are changed
Server-Side Languages
- Add support for polymorphic arguments and return types to languages other than PL/PgSQL
- Add support for OUT and INOUT parameters to languages other than PL/PgSQL
- Add more fine-grained specification of functions taking arbitrary data types
- Implement stored procedures
- This might involve the control of transaction state and the return of multiple result sets
- Allow holdable cursors in SPI
SQL-Language Functions
- Rethink query plan caching and timing of parse analysis within SQL-language functions
- They should work more like plpgsql functions do ...
PL/pgSQL
- Allow handling of %TYPE arrays, e.g. tab.col%TYPE[]
- Allow listing of record column names, and access to record columns via variables, e.g. columns := r.(*), tval2 := r.(colname)
- Allow row and record variables to be set to NULL constants, and allow NULL tests on such variables
- Because a row is not scalar, do not allow assignment from NULL-valued scalars.
- Consider keeping separate cached copies when search_path changes
- Improve handling of NULL row values vs. NULL rows
- Improve PERFORM handling of WITH queries or document limitation
PL/Perl
- Allow regex operations in plperl using UTF8 characters in non-UTF8 encoded databases
PL/Python
- Develop a trusted variant of PL/Python.
- Create a new restricted execution class that will allow passing function arguments in as locals. Passing them as globals means functions cannot be called recursively.
- Add a DB-API compliant interface on top of the SPI interface
- For functions returning a setof record with a composite type, cache the I/O functions for the composite type
PL/Tcl
- Add table function support
- Check encoding validity of values passed back to Postgres in function returns, trigger tuple changes, and SPI calls.
Clients
- Add a function like pg_get_indexdef() that report more detailed index information
- Split out pg_resetxlog output into pre- and post-sections
pg_ctl
- Improve pg_ctl's detection of running postmasters
- Add additional shutdown modes, and change the default?
psql
- Have psql \ds show all sequences and their settings
- Move psql backslash database information into the backend, use mnemonic commands?
- This would allow non-psql clients to pull the same information out of the database as psql.
- Make psql's \d commands more consistent in their handling of schemas
- Make psql's \d commands distinguish default privileges from no privileges
- ACL displays were visibly different for the two cases before we "improved" them by using array_to_string.
- Consistently display privilege information for all objects in psql
- [E] \s without arguments (display history) fails with libedit, doesn't use pager either
- Add a \set variable to control whether \s displays line numbers
- Another option is to add \# which lists line numbers, and allows command execution.
- Include the symbolic SQLSTATE name in verbose error reports
- Add prompt escape to display the client and server versions
- Add option to wrap column values at whitespace boundaries, rather than chopping them at a fixed width.
- Currently, "wrapped" format chops values into fixed widths. Perhaps the word wrapping could use the same algorithm documented in the W3C specification.
- Support the ReST table output format
- Details about the ReST format: http://docutils.sourceforge.net/rst.html#reference-documentation
- Add option to print advice for people familiar with other databases
- Add ability to edit views with \ev
- Fix FETCH_COUNT to handle SELECT ... INTO and WITH queries
- Prevent psql from sending remaining single-line multi-statement queries after reconnecting
- Consider having psql -c read .psqlrc, for consistency
- psql -f already reads .psqlrc
- Allow processing of multiple -f (file) options
- Improve line drawing characters
- Consider improving the continuation prompt
- Improve speed of tab completion by using LIKE
- [E] When psql -f filename sees the PGDMP marker, abort with an informative error like "this is a PostgreSQL custom-format dump, restore with pg_restore"
- [D] Update src/bin/psql/po/zh_CN.po file, use better native chinese translation.
pg_dump / pg_restore
- [E] Add full object name to the tag field. eg. for operators we need '=(integer, integer)', instead of just '='.
- [E] Modify pg_dump to create skeleton views for reload (which are then updated via CREATE OR REPLACE VIEW) when views have circular dependencies. This should eliminate the need for the CREATE RULE "_RETURN" hack currently used to address this issue. Thread and additional information here:
- Add pg_dumpall custom format dumps?
- Avoid using platform-dependent locale names in pg_dumpall output
- Using native locale names puts roadblocks in the way of porting a dump to another platform. One possible solution is to get CREATE DATABASE to accept some agreed-on set of locale names and fix them up to meet the platform's requirements.
- In a selective dump, allow dumping of an object and all its dependencies
- Add options like pg_restore -l and -L to pg_dump
- Stop dumping CASCADE on DROP TYPE commands in clean mode
- Allow pg_restore to load different parts of the COPY data for a single table simultaneously
- Remove support for dumping from pre-7.3 servers
- In 7.3 and later, we can get accurate dependency information from the server. pg_dump still contains a lot of crufty code to try to deal with the lack of dependency info in older servers, but the usefulness of maintaining that code grows small.
- Refactor handling of database attributes between pg_dump and pg_dumpall
- Currently only pg_dumpall emits database attributes, such as ALTER DATABASE SET commands and database-level GRANTs. Many people wish that pg_dump would do that. One proposal is to let pg_dump issue such commands if the -C switch was used, but it's unclear whether that will satisfy the demand.
- Change pg_dump so that a comment on the dumped database is applied to the loaded database, even if the database has a different name.
- This will require new backend syntax, perhaps COMMENT ON CURRENT DATABASE. This is related to the previous item.
- Allow parallel restore of tar dumps
- Preserve sparse storage of large objects over dump/restore
- Prevent PL/pgSQL comment from throwing an error in a non-superuser restore
- Delay REFRESH MATERIALIZED VIEW until dependent indexes are created
ecpg
- Docs
- Document differences between ecpg and the SQL standard and information about the Informix-compatibility module.
- Solve cardinality > 1 for input descriptors / variables?
- Add a semantic check level, e.g. check if a table really exists
- fix handling of DB attributes that are arrays
- Fix nested C comments
- [E] sqlwarn[6] should be 'W' if the PRECISION or SCALE value specified
- Make SET CONNECTION thread-aware, non-standard?
- Allow multidimensional arrays
- Implement COPY FROM STDIN
- Provide a way to specify size of a bytea parameter
- [E] Fix small memory leaks in ecpg
- Memory leaks in a short running application like ecpg are not really a problem, but make debugging more complicated
- Allow reuse of cursor name variables
libpq
- Prevent PQfnumber() from lowercasing unquoted column names
- PQfnumber() should never have been doing lowercasing, but historically it has so we need a way to prevent it
- Consider disallowing multiple queries in PQexec() as an additional barrier to SQL injection attacks
- Add PQexecf() that allows complex parameter substitution
- Add SQLSTATE and severity to errors generated within libpq itself
- Add support for interface/ipaddress binding to libpq
Triggers
- Improve storage of deferred trigger queue
- Right now all deferred trigger information is stored in backend memory. This could exhaust memory for very large trigger queues. This item involves dumping large queues into files, or doing some kind of join to process all the triggers, some bulk operation, or a bitmap.
- Allow triggers to be disabled in only the current session.
- This is currently possible by starting a multi-statement transaction, modifying the system tables, performing the desired SQL, restoring the system tables, and committing the transaction. ALTER TABLE ... TRIGGER requires a table lock so it is not ideal for this usage.
- With disabled triggers, allow pg_dump to use ALTER TABLE ADD FOREIGN KEY
- If the dump is known to be valid, allow foreign keys to be added without revalidating the data.
- Allow statement-level triggers to access modified rows
- When statement-level triggers are defined on a parent table, have them fire only on the parent table, and fire child table triggers only where appropriate
- Tighten trigger permission checks
- Allow BEFORE INSERT triggers on views
- Add database and transaction-level triggers
- Reduce locking requirements for creating a trigger
- Avoid requirement for "AFTER" trigger functions to return a value
- Allow creation of inline triggers
Inheritance
- Allow inherited tables to inherit indexes, UNIQUE constraints, and primary/foreign keys
- Honor UNIQUE INDEX on base column in INSERTs/UPDATEs on inherited table, e.g. INSERT INTO inherit_table (unique_index_col) VALUES (dup) should fail
- The main difficulty with this item is the problem of creating an index that can span multiple tables.
- Determine whether ALTER TABLE / SET SCHEMA should work on inheritance hierarchies (and thus support ONLY). If yes, implement it.
- ALTER TABLE variants sometimes support recursion and sometimes not, but this is poorly/not documented, and the ONLY marker would then be silently ignored. Clarify the documentation, and reject ONLY if it is not supported.
Indexes
- Prevent index uniqueness checks when UPDATE does not modify the column
- Uniqueness (index) checks are done when updating a column even if the column is not modified by the UPDATE. However, HOT already short-circuits this in common cases, so more work might not be helpful.
- Allow the creation of on-disk bitmap indexes which can be quickly combined with other bitmap indexes
-
Such indexes could be more compact if there are only a few distinct values. Such indexes can also be compressed. Keeping such indexes updated can be costly.
- Re: Bitmap index AM
- Bitmap index thoughts
- Stream bitmaps
- Re: Bitmapscan changes - Requesting further feedback
- Updated bitmap index patch
- Reviewing new index types (was Re: [PATCHES] Updated bitmap indexpatch)
- Bitmap Indexes: request for feedback
- http://archives.postgresql.org/message-id/800923.27831.qm@web29010.mail.ird.yahoo.com
- Allow accurate statistics to be collected on indexes with more than one column or expression indexes, perhaps using per-index statistics
- Re: Simple join optimized badly?
- Stats for multi-column indexes
- Cross-column statistics revisited
- Multi-Dimensional Histograms
- http://archives.postgresql.org/pgsql-hackers/2010-12/msg00913.php
- http://archives.postgresql.org/pgsql-hackers/2010-12/msg02179.php
- http://archives.postgresql.org/pgsql-hackers/2011-01/msg00459.php
- http://archives.postgresql.org/pgsql-hackers/2011-02/msg02054.php
- http://archives.postgresql.org/pgsql-hackers/2011-04/msg01731.php
- http://archives.postgresql.org/pgsql-hackers/2011-03/msg00894.php
- http://archives.postgresql.org/pgsql-hackers/2011-09/msg00679.php
- Consider having a larger statistics target for indexed columns and expression indexes.
- Consider smaller indexes that record a range of values per heap page, rather than having one index entry for every heap row
- This is useful if the heap is clustered by the indexed values.
- Add REINDEX CONCURRENTLY, like CREATE INDEX CONCURRENTLY
- This is difficult because you must upgrade to an exclusive table lock to replace the existing index file. CREATE INDEX CONCURRENTLY does not have this complication. This would allow index compaction without downtime.
- Allow multiple indexes to be created concurrently, ideally via a single heap scan
- pg_restore allows parallel index builds, but it is done via subprocesses, and there is no SQL interface for this. Cluster could definitely benefit from this.
- Consider sorting entries before inserting into btree index
- Allow creation of an index that can do comparisons to test if a value is between two column values
- Consider using "effective_io_concurrency" for index scans
- Currently only bitmap scans use this, which might be fine because most multi-row index scans use bitmap scans.
- Fix problem with btree page splits during checkpoints
- Allow "loose" or "skip" scans on btree indexes in which the first column has low cardinality
- Make the planner's "special index operator" mechanism extensible
- Allow index only count for indexes which doesn't support index only scan
- Improve GIN performance
- Teach GIN cost estimation about "fast scans"
- Allow unlogged indexes
GIST
- Add more GIST index support for geometric data types
- Allow GIST indexes to create certain complex index types, like digital trees (see Aoki)
- Fix performance issues in contrib/seg and contrib/cube GiST support
Hash
- Add UNIQUE capability to hash indexes
- Add hash WAL logging for crash recovery
- Allow multi-column hash indexes
Sorting
- Consider whether duplicate keys should be sorted by block/offset
- Consider being smarter about memory and external files used during sorts
- Consider detoasting keys before sorting
- Allow sorts of skinny tuples to use even more available memory.
- Now that it is not limited by MaxAllocSize, don't limit by INT_MAX either.
- http://www.postgresql.org/message-id/CA+U5nMKkRMin1pV8VMpS6_n7hcOWSG0kZS3oFL9JOa8DV6vJyQ@mail.gmail.com
Fsync
- Consider sorting writes during checkpoint
Cache Usage
- Provide a way to calculate an "estimated COUNT(*)"
- Perhaps by using the optimizer's cardinality estimates or random sampling.
- Consider automatic caching of statements at various levels:
- Parsed query tree
- Query execute plan
- Query results
- Consider increasing internal areas (NUM_CLOG_BUFFERS) when shared buffers is increased
- Consider decreasing the amount of memory used by PrivateRefCount
- Consider allowing higher priority queries to have referenced buffer cache pages stay in memory longer
- Improve cache lookup speed for sessions accessing many relations
- Fix memory leak caused by negative catcache entries
Vacuum
- Auto-fill the free space map by scanning the buffer cache or by checking pages written by the background writer
- Allow concurrent inserts to use recently created pages rather than creating new ones
- Consider having single-page pruning update the visibility map
- https://commitfest.postgresql.org/action/patch_view?id=75
- Re: visibility maps and heap_prune
- Allow VACUUM FULL and CLUSTER to update the visibility map
- Improve tracking of total relation tuple counts now that vacuum doesn't always scan the whole heap
- Bias FSM towards returning free space near the beginning of the heap file, in hopes that empty pages at the end can be truncated by VACUUM
- Consider a more compact data representation for dead tuple locations within VACUUM
- Provide more information in order to improve user-side estimates of dead space bloat in relations
- Improve locking behaviour of vacuum during trailing page truncation
- Reduce the number of table scans performed by vacuum
- Vacuum Gin indexes in physically order rather than logical order
- Avoid creation of the free space map for small tables
Auto-vacuum
- Issue log message to suggest VACUUM FULL if a table is nearly empty?
- Prevent long-lived temporary tables from causing frozen-xid advancement starvation
- The problem is that autovacuum cannot vacuum them to set frozen xids; only the session that created them can do that.
- Prevent autovacuum from running if an old transaction is still running from the last vacuum
- Have autoanalyze of parent tables occur when child tables are modified
- Allow visibility map all-visible bits to be set even when an auto-ANALYZE is running
- Allow parallel cores to be used by vacuumdb
- Improve autovacuum tuning
- Improve setting of visibility map bits for read-only and insert-only workloads
Locking
- Fix priority ordering of read and write light-weight locks
- Fix problem when multiple subtransactions of the same outer transaction hold different types of locks, and one subtransaction aborts
- Add idle_in_transaction_timeout GUC so locks are not held for long periods of time
- Improve deadlock detection when a page cleaning lock conflicts with a shared buffer that is pinned
- Detect deadlocks involving LockBufferForCleanup()
- Allow finer control over who is cancelled in a deadlock
Startup Time Improvements
- Experiment with multi-threaded backend for backend creation
- This would prevent the overhead associated with process creation. Most operating systems have trivial process creation time compared to database startup overhead, but a few operating systems (Win32, Solaris) might benefit from threading. Also explore the idea of a single session using multiple threads to execute a statement faster.
- Allow backends to change their database without restart
- This allows for faster server startup.
Write-Ahead Log
- Eliminate need to write full pages to WAL before page modification
-
Currently, to protect against partial disk page writes, we write full page images to WAL before they are modified so we can correct any partial page writes during recovery. These pages can also be eliminated from point-in-time archive files.
- Re: Index Scans become Seq Scans after VACUUM ANALYSE
- http://archives.postgresql.org/pgsql-hackers/2011-05/msg01191.php
- WIP double writes
- double writes
- Double-write with Fast Checksums
- double writes using "double-write buffer" approach
- http://archives.postgresql.org/pgsql-hackers/2012-10/msg01463.php
- When full page writes are off, write CRC to WAL and check file system blocks on recovery
- If CRC check fails during recovery, remember the page in case a later CRC for that page properly matches. The difficulty is that hint bits are not WAL logged, meaning a valid page might not match the earlier CRC.
- Write full pages during file system write and not when the page is modified in the buffer cache
- This allows most full page writes to happen in the background writer. It might cause problems for applying WAL on recovery into a partially-written page, but later the full page will be replaced from WAL.
- [D] Consider compression of full page writes
- Allow WAL information to recover corrupted pg_controldata
- Find a way to reduce rotational delay when repeatedly writing last WAL page
- Currently fsync of WAL requires the disk platter to perform a full rotation to fsync again. One idea is to write the WAL to different offsets that might reduce the rotational delay.
- Speed WAL recovery by allowing more than one page to be prefetched
- This should be done utilizing the same infrastructure used for prefetching in general to avoid introducing complex error-prone code in WAL replay.
- Improve WAL concurrency by increasing lock granularity
- Be more aggressive about creating WAL files
- Have resource managers report the duration of their status changes
- Close deleted WAL files held open in *nix by long-lived read-only backends
Optimizer / Executor
- Improve selectivity functions for geometric operators
- Consider increasing the default values of from_collapse_limit, join_collapse_limit, and/or geqo_threshold
- Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
- Log statements where the optimizer row estimates were dramatically different from the number of rows actually found?
- Consider compressed annealing to search for query plans
- This might replace GEQO.
- Improve use of expression indexes for ORDER BY
- Modify the planner to better estimate caching effects
- Allow shared buffer cache contents to affect index cost computations
- Allow the CTE (Common Table Expression) optimization fence to be optionally disabled
- Teach the planner how to better use partial indexes for index-only scans
Hashing
- Consider using a hash for joining to a large IN (VALUES ...) list
- Allow single batch hash joins to preserve outer pathkeys
- "lazy" hash tables - look up only the tuples that are actually requested
- Avoid building the same hash table more than once during the same query
- Avoid hashing for distinct and then re-hashing for hash join
Background Writer
- Consider having the background writer update the transaction status hint bits before writing out the page
- Implementing this requires the background writer to have access to system catalogs and the transaction status log.
- Consider adding buffers the background writer finds reusable to the free list
- Automatically tune bgwriter_delay based on activity rather then using a fixed interval
- Consider whether increasing BM_MAX_USAGE_COUNT improves performance
- Test to see if calling PreallocXlogFiles() from the background writer will help with WAL segment creation latency
- Add auto-tuning of work_mem
Concurrent Use of Resources
- Do async I/O for faster random read-ahead of data
-
Async I/O allows multiple I/O requests to be sent to the disk with results coming back asynchronously.
- Asynchronous I/O Support
- Re: random_page_costs - are defaults of 4.0 realistic for SCSI RAID 1
- There's random access and then there's random access
- Bitmap index scan preread using posix_fadvise (Was: There's random access and then there's random access)
The above patch is already applied as of 8.4, but it still remains to figure out how to handle plain indexscans effectively.
- Experiment with multi-threaded backend for better I/O utilization
- This would allow a single query to make use of multiple I/O channels simultaneously. One idea is to create a background reader that can pre-fetch sequential and index scan pages needed by other backends. This could be expanded to allow concurrent reads from multiple devices in a partitioned table.
- Experiment with multi-threaded backend for better CPU utilization
- This would allow several CPUs to be used for a single query, such as for sorting or query execution.
- SMP scalability improvements
TOAST
- Allow user configuration of TOAST thresholds
- Reduce unnecessary cases of deTOASTing
- Reduce costs of repeat de-TOASTing of values
Monitoring
- Expand pg_stat_activity for easier integration with monitoring tools
- Add column to pg_stat_activity that shows the progress of long-running commands like CREATE INDEX and VACUUM
- EXPLAIN progress info
- The CLUSTER/VACUUM FULL implementation would also be useful to track this way
- Have pg_stat_activity display query strings in the correct client encoding
- [E] Expose pg_controldata via an SQL interface
- Helpful for monitoring replicated databases
- Add entry creation timestamp column to pg_stat_replication
- Allow reporting of stalls due to wal_buffer wrap-around
- Restructure pg_stat_database columns tup_returned and tup_fetched to return meaningful values
Miscellaneous Performance
- Use mmap() rather than shared memory for shared buffers?
- This would remove the requirement for SYSV SHM but would introduce portability issues. Anonymous mmap (or mmap to /dev/zero) is required to prevent I/O overhead. We could also consider mmap() for writing WAL.
- Rather than consider mmap()-ing in 8k pages, consider mmap()'ing entire files into a backend?
- Doing I/O to large tables would consume a lot of address space or require frequent mapping/unmapping. Extending the file also causes mapping problems that might require mapping only individual pages, leading to thousands of mappings. Another problem is that there is no way to _prevent_ I/O to disk from the dirty shared buffers so changes could hit disk before WAL is written.
- Consider ways of storing rows more compactly on disk:
- Reduce the row header size?
- Consider reducing on-disk varlena length from four bytes to two because a heap row cannot be more than 64k in length
- Consider transaction start/end performance improvements
- Allow configuration of backend priorities via the operating system
- Though backend priorities make priority inversion during lock waits possible, research shows that this is not a huge problem.
- Consider increasing the minimum allowed number of shared buffers
- Consider if CommandCounterIncrement() can avoid its AcceptInvalidationMessages() call
- Consider Cartesian joins when both relations are needed to form an indexscan qualification for a third relation
- Consider not storing a NULL bitmap on disk if all the NULLs are trailing
- Sort large UPDATE/DELETEs so it is done in heap order
- Consider decreasing the I/O caused by updating tuple hint bits
- Hint Bits and Write I/O
- Re: [HACKERS] Hint Bits and Write I/O
- http://archives.postgresql.org/pgsql-hackers/2010-10/msg00695.php
- http://archives.postgresql.org/pgsql-hackers/2010-11/msg00792.php
- http://archives.postgresql.org/pgsql-hackers/2011-01/msg01063.php
- http://archives.postgresql.org/pgsql-hackers/2011-03/msg01408.php
- http://archives.postgresql.org/pgsql-hackers/2011-03/msg01453.php
- Avoid the requirement of freezing pages that are infrequently modified
-
If all rows on a page are visible, it is possible to set a bit in the visibility map (once the visibility map is 100% reliable) and not need to freeze the page, avoiding a page rewrite
- http://archives.postgresql.org/message-id/4BF701CF.2090205@agliodbs.com
- http://archives.postgresql.org/pgsql-hackers/2010-06/msg00082.php
- http://www.postgresql.org/message-id/20130523175148.GA29374@alap2.anarazel.de
- http://www.postgresql.org/message-id/CA+TgmoaEmnoLZmVbb8gvY69NA8zw9BWpiZ9+TLz-LnaBOZi7JA@mail.gmail.com
- http://www.postgresql.org/message-id/51A7553E.5070601@vmware.com
- Avoid reading in b-tree pages when replaying vacuum records in hot standby mode
- Restructure truncation logic to be more resistant to failure
- This also involves not writing dirty buffers for a truncated or dropped relation
- Consider adding logic to increase large tables by more than 8k
- This would reduce file system fragmentation
Miscellaneous Other
- Deal with encoding issues for filenames in the server filesystem
- Deal with encoding issues in the output of localeconv()
- Provide schema name and other fields available from SQL GET DIAGNOSTICS in error reports
- Add 64-bit support to /contrib/pgbench
- Use sa_mask to close race conditions between signal handlers
Source Code
- [E] Remove warnings created by -Wcast-align
- Move platform-specific ps status display info from ps_status.c to ports
- Consider a faster CRC32 algorithm
- Allow cross-compiling by generating the zic database on the target system
- Improve NLS maintenance of libpgport messages linked onto applications
- Use UTF8 encoding for NLS messages so all server encodings can read them properly
- Allow creation of universal binaries for Darwin
- Consider GnuTLS if OpenSSL license becomes a problem
- Consider making NAMEDATALEN more configurable in future releases
- Research use of signals and sleep wake ups
- Allow C++ code to more easily access backend code
- Consider simplifying how memory context resets handle child contexts
- Create three versions of libpgport to simplify client code
- Improve detection of shared memory segments being used by others by checking the SysV shared memory field 'nattch'
- Implement the non-threaded Avahi service discovery protocol
- Reduce data row alignment requirements on some 64-bit systems
- Restructure TOAST internal storage format for greater flexibility
- Add regression tests for pg_dump/restore
- Research different memory allocation methods for lists
- Consider removing the attribute options cache
- Restructure /contrib section
- Consider adding explicit huge page support
/contrib/pg_upgrade
- Handle large object comments
- This is difficult to do because the large object doesn't exist when --schema-only is loaded.
- Consider using pg_depend for checking object usage in version.c
- If reindex is necessary, allow it to be done in parallel with pg_dump custom format
- Migrate pg_statistic by dumping it out as a flat file, so analyze is not necessary
- pg_class.oid is not preserved so schema.tablename must be used.
- Improve testing, perhaps using the buildfarm
- The buildfarm has access to multiple versions of PostgreSQL.
- Create machine-readable output of pg_controldata
- This would avoid parsing its output. The problem is we need pg_controldata output from both the old and new clusters so we would need to support both formats.
- Find cleaner way to start/stop dedicated servers for upgrades
- Desired changes that would prevent upgrades with pg_upgrade
- 32-bit page checksums
- Add metapage to GiST indexes
- Clean up hstore's internal representation
- Remove tuple infomask bit HEAP_MOVED_OFF and HEAP_MOVED_IN
- fix char() index trailing space handling
- Use non-collation-aware comparisons for GIN opclasses
Windows
- Remove configure.in check for link failure when cause is found
- Remove readdir() errno patch when runtime/mingwex/dirent.c rev 1.4 is released
- Allow psql to use readline once non-US code pages work with backslashes
- Fix problem with shared memory on the Win32 Terminal Server
- Improve signal handling
- Convert MSVC build system to remove most batch files
- Support pgxs when using MSVC
- Fix MSVC NLS support, like for to_char()
- Find a correct rint() substitute on Windows
- Fix global namespace issues when using multiple terminal server sessions
- Change from the current autoconf/gmake build system to cmake
- Improve consistency of path separator usage
- Fix cross-compiling on Windows
- Reduce file statistics overhead on directory reads
- Fix hang with long file paths
Wire Protocol Changes
- Allow dynamic character set handling
- Ensure the client can determine the encoding of messages sent early in the handshake
- Let the client indicate character encoding of database names, user names, passwords, and of pre-auth error messages returned by the server
- Add decoded type, length, precision
- Mark result columns as known-not-null when possible
- Provide more control over planner treatment of statements being prepared
- Use compression
- If SSL is used, hopefully avoid the overhead of key negotiation and encryption
- Update clients to use data types, typmod, schema.table.column names of result sets using new statement protocol
- Set protocol for wire format negotiation
- Make sure upgrading to a 4.1 protocol version will actually work smoothly
- Allow multi-state authentication (e.g. try client peer, fall back to md5)
- Identify the affected object in CommandComplete message?
- Allow negotiation of encryption, STARTTLS style, rather than forcing client to decide on SSL or !SSL before connecting
- Permit lazy fetches of large values, at least out-of-line TOASTED values
Documentation
- [E] Add contrib functions to the index
- Add the functions and GUCs in the contrib modules to the documentation index: per list discussion
- Convert single quotes to apostrophes in the PDF documentation
- Provide a manpage for postgresql.conf
- Change the manpage-generating toolchain to use the new XML-based docbook2x tools
- Consider changing documentation format from SGML to XML
- Document support for N' ' national character string literals, if it matches the SQL standard
- Add diagrams to the documentation
Exotic Features
- Add pre-parsing phase that converts non-ISO syntax to supported syntax
- This could allow SQL written for other databases to run without modification.
- Allow plug-in modules to emulate features from other databases
- Add features of Oracle-style packages
- A package would be a schema with session-local variables, public/private functions, and initialization functions. It is also possible to implement these capabilities in any schema and not use a separate "packages" syntax at all.
- Consider allowing control of upper/lower case folding of unquoted identifiers
- Add autonomous transactions
- Give query progress indication
- Rethink our type system
- Improve push-down of joins, aggregates, and sorts to foreign data wrappers
Features We Do Not Want
The following features have been discussed ad nauseum on the PostgreSQL mailing lists and the consensus has been that the project is not interested in them. As such, if you are going to bring them up as potential features, you will want to be familiar with all of the arguments against these features which have been previously made over the years. If you decide to work on such features anyway, you should be aware that you face a higher-than-normal barrier to get the Project to accept them.
- All backends running as threads in a single process (not wanted)
- This eliminates the process protection we get from the current setup. Thread creation is usually the same overhead as process creation on modern systems, so it seems unwise to use a pure threaded model, and MySQL and DB2 have demonstrated that threads introduce as many issues as they solve. Threading specific operations such as I/O, seq scans, and connection management has been discussed and will probably be implemented to enable specific performance features. Moving to a threaded engine would also require halting all other work on PostgreSQL for one to two years.
- "Oracle-style" optimizer hints (not wanted)
- Optimizer hints, as implemented in Oracle and other RDBMSes, are used to work around problems in the optimizer and introduce upgrade and maintenance issues. We would rather have such problems reported and fixed. We have discussed a more sophisticated system of per-class cost adjustment instead, but a specification remains to be developed. See Optimizer Hints Discussion for further information.
- Embedded server (not wanted)
- While PostgreSQL clients runs fine in limited-resource environments, the server requires multiple processes and a stable pool of resources to run reliably and efficiently. Stripping down the PostgreSQL server to run in the same process address space as the client application would add too much complexity and failure cases. Besides, there are several very mature embedded SQL databases already available.
- Obfuscated function source code (not wanted)
- Obfuscating function source code has minimal protective benefits because anyone with super-user access can find a way to view the code. At the same time, it would greatly complicate backups and other administrative tasks. To prevent non-super-users from viewing function source code, remove SELECT permission on pg_proc.
- Indeterminate behavior for the GROUP BY clause (not wanted)
- At least one other database product allows specification of a subset of the result columns which GROUP BY would need to be able to provide predictable results; the server is free to return any value from the group. This is not viewed as a desirable feature. PostgreSQL 9.1 allows result columns that are not referenced by GROUP BY if a primary key for the same table is referenced in GROUP BY.
