NameUNLISTEN -- stop listening for a notification Synopsis UNLISTEN { channel | * } Description UNLISTEN is used to remove an existing registration for NOTIFY events. UNLISTEN cancels any existing registration of the current PostgreSQL session as a listener on the notification channel named channel. The special wildcard * cancels all listener registrations for the current session. NOTIFY contains a more extensive discussion of the use of LISTEN and NOTIFY. Parameters channel Name

unaccent is a text search dictionary that removes accents (diacritic signs) from lexemes. It's a filtering dictionary, which means its output is always passed to the next dictionary (if any), unlike the normal behavior of dictionaries. This allows accent-insensitive processing for full text search. The current implementation of unaccent cannot be used as a normalizing dictionary for the thesaurus dictionary. F.44.1. Configuration An unaccent dictionary accepts the following options: RULES is

The modification of data that is already in the database is referred to as updating. You can update individual rows, all the rows in a table, or a subset of all rows. Each column can be updated separately; the other columns are not affected. To update existing rows, use the UPDATE command. This requires three pieces of information: The name of the table and column to update The new value of the column Which row(s) to update Recall from Chapter 5 that SQL does not, in general, provide a

The specific operator that is referenced by an operator expression is determined using the following procedure. Note that this procedure is indirectly affected by the precedence of the operators involved, since that will determine which sub-expressions are taken to be the inputs of which operators. See Section 4.1.6 for more information. Operator Type Resolution Select the operators to be considered from the pg_operator system catalog. If a non-schema-qualified operator name was used (the us

SQL is a strongly typed language. That is, every data item has an associated data type which determines its behavior and allowed usage. PostgreSQL has an extensible type system that is more general and flexible than other SQL implementations. Hence, most type conversion behavior in PostgreSQL is governed by general rules rather than by ad hoc heuristics. This allows the use of mixed-type expressions even with user-defined types. The PostgreSQL scanner/parser divides lexical elements into five f

Values to be inserted into a table are converted to the destination column's data type according to the following steps. Value Storage Type Conversion Check for an exact match with the target. Otherwise, try to convert the expression to the target type. This is possible if an assignment cast between the two types is registered in the pg_cast catalog (see CREATE CAST). Alternatively, if the expression is an unknown-type literal, the contents of the literal string will be fed to the input con

SQL UNION constructs must match up possibly dissimilar types to become a single result set. The resolution algorithm is applied separately to each output column of a union query. The INTERSECT and EXCEPT constructs resolve dissimilar types in the same way as UNION. The CASE, ARRAY, VALUES, GREATEST and LEAST constructs use the identical algorithm to match up their component expressions and select a result data type. Type Resolution for UNION, CASE, and Related Constructs If all inputs are of

The specific function that is referenced by a function call is determined using the following procedure. Function Type Resolution Select the functions to be considered from the pg_proc system catalog. If a non-schema-qualified function name was used, the functions considered are those with the matching name and argument count that are visible in the current search path (see Section 5.8.3). If a qualified function name was given, only functions in the specified schema are considered. If the s

The tsearch2 module provides backwards-compatible text search functionality for applications that used tsearch2 before text searching was integrated into core PostgreSQL in release 8.3. F.41.1. Portability Issues Although the built-in text search features were based on tsearch2 and are largely similar to it, there are numerous small differences that will create portability issues for existing applications: Some functions' names were changed, for example rank to ts_rank. The replacement tsearc

NameTRUNCATE -- empty a table or set of tables Synopsis TRUNCATE [ TABLE ] [ ONLY ] name [ * ] [, ... ] [ RESTART IDENTITY | CONTINUE IDENTITY ] [ CASCADE | RESTRICT ] Description TRUNCATE quickly removes all rows from a set of tables. It has the same effect as an unqualified DELETE on each table, but since it does not actually scan the tables it is faster. Furthermore, it reclaims disk space immediately, rather than requiring a subsequent VACUUM operation. This is most useful on