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FDW Routines for EXPLAINManual ChaptersPG1858.2.7. FDW Routines for EXPLAIN void ExplainForeignScan(ForeignScanState *node, ExplainState *es); Print additional EXPLAIN output for a foreign table scan. This function can call ExplainPr…FDW Routines for EXPLAIN FDW Routines for IMPORT FOREIGN SCHEMAManual ChaptersPG1858.2.9. FDW Routines for IMPORT FOREIGN SCHEMA List * ImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid); Obtain a list of foreign table creation commands. This function is ca…FDW Routines for IMPORT FOREIGN SCHEMA FDW Routines for Parallel ExecutionManual ChaptersPG1858.2.10. FDW Routines for Parallel Execution A ForeignScan node can, optionally, support parallel execution. A parallel ForeignScan will be executed in multiple processes and must return eac…FDW Routines for Parallel Execution FDW Routines for Planning Post-Scan/Join ProcessingManual ChaptersPG1858.2.3. FDW Routines for Planning Post-Scan/Join Processing If an FDW supports performing remote post-scan/join processing, such as remote aggregation, it should provide this callback functi…FDW Routines for Planning Post-Scan/Join Processing FDW Routines for Reparameterization of PathsManual ChaptersPG1858.2.12. FDW Routines for Reparameterization of Paths List * ReparameterizeForeignPathByChild(PlannerInfo *root, List *fdw_private, RelOptInfo *child_rel); This function is called while conv…FDW Routines for Reparameterization of Paths FDW Routines for Row LockingManual ChaptersPG1858.2.6. FDW Routines for Row Locking If an FDW wishes to support late row locking (as described in Section 58.5), it must provide the following callback functions: RowMarkType GetForeignRowM…FDW Routines for Row Locking FDW Routines for Scanning Foreign JoinsManual ChaptersPG1858.2.2. FDW Routines for Scanning Foreign Joins If an FDW supports performing foreign joins remotely (rather than by fetching both tables' data and doing the join locally), it should provide…FDW Routines for Scanning Foreign Joins FDW Routines for Scanning Foreign TablesManual ChaptersPG1858.2.1. FDW Routines for Scanning Foreign Tables void GetForeignRelSize(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid); Obtain relation size estimates for a foreign table. This …FDW Routines for Scanning Foreign Tables FDW Routines for TRUNCATEManual ChaptersPG1858.2.5. FDW Routines for TRUNCATE void ExecForeignTruncate(List *rels, DropBehavior behavior, bool restart_seqs); Truncate foreign tables. This function is called when TRUNCATE is executed o…FDW Routines for TRUNCATE FDW Routines for Updating Foreign TablesManual ChaptersPG1858.2.4. FDW Routines for Updating Foreign Tables If an FDW supports writable foreign tables, it should provide some or all of the following callback functions depending on the needs and capa…FDW Routines for Updating Foreign Tables FeaturesManual ChaptersPG18F.40.5. FeaturesFeatures FETCHManual ChaptersPG1841.7.3.1. FETCH FETCH [ direction { FROM | IN } ] cursor INTO target; FETCH retrieves the next row (in the indicated direction) from the cursor into a target, which might be a row variable, …FETCH FETCHManual ChaptersPG18FETCH FETCH — retrieve rows from a query using a cursor Synopsis FETCH [ direction ] [ FROM | IN ] cursor_name where direction can be one of: NEXT PRIOR FIRST LAST ABSOLUTE count RELATIVE co…FETCH Field SelectionManual ChaptersPG184.2.4. Field Selection If an expression yields a value of a composite type (row type), then a specific field of the row can be extracted by writing expression.fieldname In general the row ex…Field Selection File FormatsManual ChaptersPG18File FormatsFile Formats File HeaderManual ChaptersPG18File Header The file header consists of 15 bytes of fixed fields, followed by a variable-length header extension area. The fixed fields are: Signature 11-byte sequence PGCOPY\n\377\r\n\0 — n…File Header File LocationsManual ChaptersPG1819.2. File Locations In addition to the postgresql.conf file already mentioned, PostgreSQL uses two other manually-edited configuration files, which control client authentication (their use …File Locations File System Level BackupManual ChaptersPG1825.2. File System Level Backup An alternative backup strategy is to directly copy the files that PostgreSQL uses to store the data in the database; Section 18.2 explains where these files ar…File System Level Backup File SystemsManual ChaptersPG1818.2.2. File Systems Generally, any file system with POSIX semantics can be used for PostgreSQL. Users prefer different file systems for a variety of reasons, including vendor support, perfo…File Systems File TrailerManual ChaptersPG18File Trailer The file trailer consists of a 16-bit integer word containing -1. This is easily distinguished from a tuple's field-count word. A reader should report an error if a field-count …File Trailer file_fdw — access data files in the server's file systemManual ChaptersPG18F.15. file_fdw — access data files in the server's file system The file_fdw module provides the foreign-data wrapper file_fdw, which can be used to access data files in the server's file sys…file_fdw — access data files in the server's file system FilesManual ChaptersPG18Files postmaster.pid pg_ctl examines this file in the data directory to determine whether the server is currently running. postmaster.opts If this file exists in the data directory, pg_ctl (…Files FilesManual ChaptersPG18Files psqlrc and ~/.psqlrc # Unless it is passed an -X option, psql attempts to read and execute commands from the system-wide startup file (psqlrc) and then the user's personal startup file…Files Floating-Point DifferencesManual ChaptersPG1831.2.4. Floating-Point Differences Some of the tests involve computing 64-bit floating-point numbers (double precision) from table columns. Differences in results involving mathematical func…Floating-Point Differences Floating-Point TypesManual ChaptersPG188.1.3. Floating-Point Types The data types real and double precision are inexact, variable-precision numeric types. On all currently supported platforms, these types are implementations of I…Floating-Point Types FOR (Integer Variant)Manual ChaptersPG1841.6.5.5. FOR (Integer Variant) [ <<label>> ] FOR name IN [ REVERSE ] expression .. expression [ BY expression ] LOOP statements END LOOP [ label ]; This form of FOR creates a loop that iter…FOR (Integer Variant) FOR NO KEY UPDATE, FOR UPDATE, FOR SHARE, FOR KEY SHAREManual ChaptersPG18FOR NO KEY UPDATE, FOR UPDATE, FOR SHARE, FOR KEY SHARE Although FOR UPDATE appears in the SQL standard, the standard allows it only as an option of DECLARE CURSOR. PostgreSQL allows it in a…FOR NO KEY UPDATE, FOR UPDATE, FOR SHARE, FOR KEY SHARE For the ProgrammerManual ChaptersPG1856.2. For the ProgrammerFor the Programmer For the TranslatorManual ChaptersPG1856.1. For the Translator PostgreSQL programs (server and client) can issue their messages in your favorite language — if the messages have been translated. Creating and maintaining translate…For the Translator Foreign DataManual ChaptersPG185.13. Foreign Data PostgreSQL implements portions of the SQL/MED specification, allowing you to access data that resides outside PostgreSQL using regular SQL queries. Such data is referred t…Foreign Data Foreign Data Wrapper Callback RoutinesManual ChaptersPG1858.2. Foreign Data Wrapper Callback Routines The FDW handler function returns a palloc'd FdwRoutine struct containing pointers to the callback functions described below. The scan-related fun…Foreign Data Wrapper Callback Routines Foreign Data Wrapper FunctionsManual ChaptersPG1858.1. Foreign Data Wrapper Functions The FDW author needs to implement a handler function, and optionally a validator function. Both functions must be written in a compiled language such as …Foreign Data Wrapper Functions Foreign Data Wrapper Helper FunctionsManual ChaptersPG1858.3. Foreign Data Wrapper Helper Functions Several helper functions are exported from the core server so that authors of foreign data wrappers can get easy access to attributes of FDW-relat…Foreign Data Wrapper Helper Functions Foreign Data Wrapper Query PlanningManual ChaptersPG1858.4. Foreign Data Wrapper Query Planning The FDW callback functions GetForeignRelSize, GetForeignPaths, GetForeignPlan, PlanForeignModify, GetForeignJoinPaths, GetForeignUpperPaths, and Pla…Foreign Data Wrapper Query Planning Foreign Key ConstraintsManual ChaptersPG18Foreign Key Constraints The ability to specify column lists in the foreign key actions SET DEFAULT and SET NULL is a PostgreSQL extension. It is a PostgreSQL extension that a foreign key con…Foreign Key Constraints Foreign KeysManual ChaptersPG185.5.5. Foreign Keys A foreign key constraint specifies that the values in a column (or a group of columns) must match the values appearing in some row of another table. We say this maintains…Foreign Keys Foreign KeysManual ChaptersPG183.3. Foreign Keys Recall the weather and cities tables from Chapter 2. Consider the following problem: You want to make sure that no one can insert rows in the weather table that do not have…Foreign Keys foreign_data_wrapper_optionsManual ChaptersPG1835.26. foreign_data_wrapper_options The view foreign_data_wrapper_options contains all the options defined for foreign-data wrappers in the current database. Only those foreign-data wrappers…foreign_data_wrapper_options foreign_data_wrappersManual ChaptersPG1835.27. foreign_data_wrappers The view foreign_data_wrappers contains all foreign-data wrappers defined in the current database. Only those foreign-data wrappers are shown that the current us…foreign_data_wrappers foreign_server_optionsManual ChaptersPG1835.28. foreign_server_options The view foreign_server_options contains all the options defined for foreign servers in the current database. Only those foreign servers are shown that the curr…foreign_server_options