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Diffstat (limited to 'src/bin/pgaccess/lib/help/create_index.hlp')
-rw-r--r-- | src/bin/pgaccess/lib/help/create_index.hlp | 87 |
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diff --git a/src/bin/pgaccess/lib/help/create_index.hlp b/src/bin/pgaccess/lib/help/create_index.hlp deleted file mode 100644 index 65548a5466e..00000000000 --- a/src/bin/pgaccess/lib/help/create_index.hlp +++ /dev/null @@ -1,87 +0,0 @@ -.pgaw:Help.f.t insert end "CREATE INDEX" {bold} " constructs an index index_name. on the specified table. - - Tip: Indexes are primarily used to enhance database performance. But inappropriate use will result in slower performance. - - In the first syntax shown above, the key fields for the index are specified as column names; a column may also have an associated operator class. An operator class is used to specify the \ -operators to be used for a particular index. For example, a btree index on four-byte integers would use the int4_ops class; this operator class includes comparison functions for four-byte \ -integers. The default operator class is the appropriate operator class for that field type. - - In the second syntax, an index is defined on the result of a user-defined function func_name applied to one or more attributes of a single class. These functional indexes can be used to obtain \ -fast access to data based on operators that would normally require some transformation to apply them to the base data. - -" {} "Synopsis" {bold} " - -CREATE \[ UNIQUE \] INDEX index_name - ON table \[ USING acc_name \] - ( column \[ ops_name\] \[, ...\] ) -CREATE \[ UNIQUE \] INDEX index_name - ON table \[ USING acc_name \] - ( func_name( column \[, ... \]) ops_name ) - -" {code} "Inputs" {bold} " - -" {} "UNIQUE" {italic} " - Causes the system to check for duplicate values in the table when the index is created \ - \(if data already exist\) and each time data is added. Attempts to insert or update non-duplicate \ - data will generate an error. - -" {} "index_name" {italic} " - The name of the index to be created. - -" {} "table" {italic} " - The name of the table to be indexed. - -" {} "acc_name" {italic} " - the name of the access method which is to be used for the index. The default access method is BTREE. Postgres provides three access methods for secondary indexes: - - BTREE - - an implementation of the Lehman-Yao high-concurrency btrees. - - RTREE - - implements standard rtrees using Guttman's quadratic split algorithm. - - HASH - - an implementation of Litwin's linear hashing. - -" {} "column" {italic} " - The name of a column of the table. - -" {} "ops_name" {italic} " - An associated operator class. The following select list returns all ops_names: -" {} " - SELECT am.amname AS acc_name, - opc.opcname AS ops_name, - opr.oprname AS ops_comp - FROM pg_am am, pg_amop amop, - pg_opclass opc, pg_operator opr - WHERE amop.amopid = am.oid AND - amop.amopclaid = opc.oid AND - amop.amopopr = opr.oid - ORDER BY acc_name, ops_name, ops_comp - -" {code} "func_name" {italic} " - A user-defined function, which returns a value that can be indexed. - -" {} "Outputs" {bold} " - -" {} "CREATE" {italic} " - The message returned if the index is successfully created. - -" {} "ERROR: Cannot create index: 'index_name' already exists." {italic} " - This error occurs if it is impossible to create the index. - -" {} "Usage" {bold} " - -To create a btree index on the field title in the table films: -" {} " -CREATE UNIQUE INDEX title_idx - ON films (title); - -" {code} "Notes" {bold} " - -Currently, only the BTREE access method supports multi-column indexes. Up to 7 keys may be specified. - -Use DROP INDEX to remove an index. " |