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TablespacesManual ChaptersPG1822.6. Tablespaces Tablespaces in PostgreSQL allow database administrators to define locations in the file system where the files representing database objects can be stored. Once created, a …Tablespaces TablespacesManual ChaptersPG18Tablespaces The PostgreSQL concept of tablespaces is not part of the standard. Hence, the clauses TABLESPACE and USING INDEX TABLESPACE are extensions.Tablespaces TAP TestsManual ChaptersPG1831.4. TAP Tests Various tests, particularly the client program tests under src/bin, use the Perl TAP tools and are run using the Perl testing program prove. You can pass command-line options…TAP Tests Tcl Procedure NamesManual ChaptersPG1842.12. Tcl Procedure Names In PostgreSQL, the same function name can be used for different function definitions if the functions are placed in different schemas, or if the number of argument…Tcl Procedure Names tcn — a trigger function to notify listeners of changes to table contentManual ChaptersPG18F.44. tcn — a trigger function to notify listeners of changes to table content The tcn module provides a trigger function that notifies listeners of changes to any table on which it is attac…tcn — a trigger function to notify listeners of changes to table content TCP SettingsManual ChaptersPG1819.3.2. TCP Settings tcp_keepalives_idle (integer) # Specifies the amount of time with no network activity after which the operating system should send a TCP keepalive message to the client.…TCP Settings Template DatabasesManual ChaptersPG1822.3. Template Databases CREATE DATABASE actually works by copying an existing database. By default, it copies the standard system database named template1. Thus that database is the “templa…Template Databases Temporary TablesManual ChaptersPG18Temporary Tables Although the syntax of CREATE TEMPORARY TABLE resembles that of the SQL standard, the effect is not the same. In the standard, temporary tables are defined just once and aut…Temporary Tables TerminationManual ChaptersPG1854.2.9. Termination The normal, graceful termination procedure is that the frontend sends a Terminate message and immediately closes the connection. On receipt of this message, the backend c…Termination Test Coverage ExaminationManual ChaptersPG1831.5. Test Coverage Examination The PostgreSQL source code can be compiled with coverage testing instrumentation, so that it becomes possible to examine which parts of the code are covered b…Test Coverage Examination Test EvaluationManual ChaptersPG1831.2. Test Evaluation Some properly installed and fully functional PostgreSQL installations can “fail” some of these regression tests due to platform-specific artifacts such as varying float…Test Evaluation test_decoding — SQL-based test/example module for WAL logical decodingManual ChaptersPG18F.45. test_decoding — SQL-based test/example module for WAL logical decoding test_decoding is an example of a logical decoding output plugin. It doesn't do anything especially useful, but ca…test_decoding — SQL-based test/example module for WAL logical decoding Testing and Debugging Text SearchManual ChaptersPG1812.8. Testing and Debugging Text Search The behavior of a custom text search configuration can easily become confusing. The functions described in this section are useful for testing text se…Testing and Debugging Text Search Text FormatManual ChaptersPG18Text Format When the text format is used, the data read or written is a text file with one line per table row. Columns in a row are separated by the delimiter character. The column values th…Text Format Text Search Functions and OperatorsManual ChaptersPG189.13. Text Search Functions and Operators Table 9.42, Table 9.43 and Table 9.44 summarize the functions and operators that are provided for full text searching. See Chapter 12 for a detailed…Text Search Functions and Operators Text Search IntegrationManual ChaptersPG18F.35.5. Text Search Integration Trigram matching is a very useful tool when used in conjunction with a full text index. In particular it can help to recognize misspelled input words that wil…Text Search Integration Text Search TypesManual ChaptersPG188.11. Text Search Types PostgreSQL provides two data types that are designed to support full text search, which is the activity of searching through a collection of natural-language document…Text Search Types The Autovacuum DaemonManual ChaptersPG1824.1.6. The Autovacuum Daemon PostgreSQL has an optional but highly recommended feature called autovacuum, whose purpose is to automate the execution of VACUUM and ANALYZE commands. When ena…The Autovacuum Daemon The Berkeley POSTGRES ProjectManual ChaptersPG182.1. The Berkeley POSTGRES Project The POSTGRES project, led by Professor Michael Stonebraker, was sponsored by the Defense Advanced Research Projects Agency (DARPA), the Army Research Offic…The Berkeley POSTGRES Project The ConceptManual ChaptersPG1834.1. The Concept An embedded SQL program consists of code written in an ordinary programming language, in this case C, mixed with SQL commands in specially marked sections. To build the pro…The Concept The Connection Service FileManual ChaptersPG1832.17. The Connection Service File The connection service file allows libpq connection parameters to be associated with a single service name. That service name can then be specified using t…The Connection Service File The Cumulative Statistics SystemManual ChaptersPG1827.2. The Cumulative Statistics System PostgreSQL's cumulative statistics system supports collection and reporting of information about server activity. Presently, accesses to tables and ind…The Cumulative Statistics System The date TypeManual ChaptersPG1834.6.3. The date Type The date type in C enables your programs to deal with data of the SQL type date. See Section 8.5 for the equivalent type in the PostgreSQL server. The following functio…The date Type The decimal TypeManual ChaptersPG1834.6.6. The decimal Type The decimal type is similar to the numeric type. However it is limited to a maximum precision of 30 significant digits. In contrast to the numeric type which can be …The decimal Type The define and undef DirectivesManual ChaptersPG1834.9.2. The define and undef Directives Similar to the directive #define that is known from C, embedded SQL has a similar concept: EXEC SQL DEFINE name; EXEC SQL DEFINE name value; So you ca…The define and undef Directives The Fast-Path InterfaceManual ChaptersPG1832.8. The Fast-Path Interface PostgreSQL provides a fast-path interface to send simple function calls to the server. Warning This interface is unsafe and should not be used. When result_is_i…The Fast-Path Interface The FROM ClauseManual ChaptersPG187.2.1. The FROM Clause The FROM clause derives a table from one or more other tables given in a comma-separated table reference list. FROM table_reference [, table_reference [, ...]] A table…The FROM Clause The GROUP BY and HAVING ClausesManual ChaptersPG187.2.3. The GROUP BY and HAVING Clauses After passing the WHERE filter, the derived input table might be subject to grouping, using the GROUP BY clause, and elimination of group rows using th…The GROUP BY and HAVING Clauses The Information SchemaManual ChaptersPG18Chapter 35. The Information Schema The information schema consists of a set of views that contain information about the objects defined in the current database. The information schema is def…The Information Schema The Initialization ForkManual ChaptersPG1866.5. The Initialization Fork Each unlogged table, and each index on an unlogged table, has an initialization fork. The initialization fork is an empty table or index of the appropriate type…The Initialization Fork The interval TypeManual ChaptersPG1834.6.5. The interval Type The interval type in C enables your programs to deal with data of the SQL type interval. See Section 8.5 for the equivalent type in the PostgreSQL server. The follo…The interval Type The Locking ClauseManual ChaptersPG18The Locking Clause FOR UPDATE, FOR NO KEY UPDATE, FOR SHARE and FOR KEY SHARE are locking clauses; they affect how SELECT locks rows as they are obtained from the table. The locking clause h…The Locking Clause The numeric TypeManual ChaptersPG1834.6.2. The numeric Type The numeric type offers to do calculations with arbitrary precision. See Section 8.1 for the equivalent type in the PostgreSQL server. Because of the arbitrary preci…The numeric Type The Parser StageManual ChaptersPG1851.3. The Parser Stage The parser stage consists of two parts: The parser defined in gram.y and scan.l is built using the Unix tools bison and flex. The transformation process does modificat…The Parser Stage The Password FileManual ChaptersPG1832.16. The Password File The file .pgpass in a user's home directory can contain passwords to be used if the connection requires a password (and no password has been specified otherwise). On…The Password File The Path of a QueryManual ChaptersPG1851.1. The Path of a Query Here we give a short overview of the stages a query has to pass to obtain a result. A connection from an application program to the PostgreSQL server has to be esta…The Path of a Query The pg_buffercache ViewManual ChaptersPG18F.25.1. The pg_buffercache View The definitions of the columns exposed by the view are shown in Table F.14. Table F.14. pg_buffercache Columns Column Type Description bufferid integer ID, in…The pg_buffercache View The pg_buffercache_evict() FunctionManual ChaptersPG18F.25.5. The pg_buffercache_evict() Function The pg_buffercache_evict() function takes a buffer identifier, as shown in the bufferid column of the pg_buffercache view. It returns information …The pg_buffercache_evict() Function The pg_buffercache_evict_all() FunctionManual ChaptersPG18F.25.7. The pg_buffercache_evict_all() Function The pg_buffercache_evict_all() function is very similar to the pg_buffercache_evict() function. The difference is, the pg_buffercache_evict_al…The pg_buffercache_evict_all() Function The pg_buffercache_evict_relation() FunctionManual ChaptersPG18F.25.6. The pg_buffercache_evict_relation() Function The pg_buffercache_evict_relation() function is very similar to the pg_buffercache_evict() function. The difference is that the pg_buffer…The pg_buffercache_evict_relation() Function