diff --git a/doc/src/sgml/glossary.sgml b/doc/src/sgml/glossary.sgml index 612ce6e5f4..05fca33d9b 100644 --- a/doc/src/sgml/glossary.sgml +++ b/doc/src/sgml/glossary.sgml @@ -6,25 +6,34 @@ systems in general. - - Aggregate + + Aggregating - To combine a collection of data values into a single value, whose - value may not be of the same type as the original values. - Aggregate Functions - combine multiple Rows that share a common set - of values into one Row, which means that the - only data visible in the values in common, and the aggregates of the - non-common data. + The act of combining a collection of data (input) values into + a single output value, which may not be of the same type as the + input values. + + + + + + Aggregate Function + + A Function that combines multiple input values, + for example by counting, averaging or adding them all together, + yielding a single output value. For more information, see . + + See also Window Function. + Archiver - A process that backs up WAL Files in order to - reclaim space on the file system. + A process that saves aside copies of WAL Files, + for the purposes of creating backup copies or keeping + Replicas current. For more information, see @@ -59,16 +70,15 @@ In reference to the value of an Attribute or - Datum: cannot be broken down into smaller - components. + Datum: the property that it cannot be broken down + into smaller components. In reference to an operation: An event that cannot be completed in part: it must either entirely succeed or entirely fail. A series of SQL statements can be combined into a Transaction, and that - transaction is said to be - Atomic. + transaction is said to be atomic. @@ -112,6 +122,7 @@ + Background Worker @@ -142,8 +154,9 @@ Background Writer - Writes continuously dirty pages from Shared - Memory to the file system. It starts periodically, but + A process that continuously writes dirty pages from + Shared Memory to the file system. + It starts periodically, but works only for a short period in order to distribute expensive I/O activity over time instead of generating fewer large I/O peaks which could block other processes. @@ -218,10 +231,9 @@ Checkpoint - A Checkpoint is a point in time - when all older dirty pages of the Shared - Memory, all older WAL records, and - a special Checkpoint record have been written + A point in time when all older dirty pages of the + Shared Memory, all older WAL records, + and a special Checkpoint record have been written and flushed to disk. @@ -543,8 +555,8 @@ A Relation that contains data derived from a - Table (or Relation such - as a Materialized View). It's internal + Table (or other kind of Relation + such as a Materialized View). Its internal structure supports very fast retrieval of and access to the original data. @@ -815,7 +827,7 @@ Record - See Tupple. + See Tuple. A single Row of a Table @@ -944,7 +956,7 @@ Row - See Tupple. + See Tuple. @@ -1194,9 +1206,9 @@ Session or a Transaction, as defined at creation time. The data in them is not visible to other Sessions, - and is not Logged. Temporary - Tables are most often used to store intermediate data for - a multi-step data transformation. + and is not Logged. + Temporary Tables are often used to store + intermediate data for a multi-step data transformation. For more information, see @@ -1227,8 +1239,9 @@ A Function which can be defined to execute whenever a certain operation (INSERT, - UPDATE, or DELTE) is applied to - that Relation. A Trigger + UPDATE, DELETE, + TRUNCATE) is applied to a Relation. + A Trigger executes within the same Transaction as the statement which invoked it, and if the Function fails then the invoking statement also fails. @@ -1249,8 +1262,8 @@ the Tuple is found, in which case the Tuple is often called a Row or Record. It may - also be defined by the structure of a Result - Set. + also be defined by the structure of a + Result Set. @@ -1260,7 +1273,7 @@ The condition of having no matching values in the same - Relation. Most often used in the concept of + Relation. Often used in the concept of Unique Indexes.