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PG_CONNECT

PG_CONNECT

okt 13, 2017

PG_CONNECT action

Function

The function establishes the connection to a table.

Declaration

PG_CONNECT dbObjIdent, accessIdent_Int, handleIdent_Int, pgSizeIdent_Int, whereIdent_Str, orderByIdent_Str, rowsCountIdent_Int, retCodeIdent_Int [TRANS transHandle_Int] [MODE mode_Int] [ORAHINT hintIdent_Str]

 

Parameters

dbObjIdent

in

Reference to an object of Database table type.

accessIdent_Int

in

Value identifier: required access to the table (_DB_READ, _DB_MODIFY).

handleIdent_Int

out

Identifier for an unique number (handle) of the connection to the table.

pgSizeIdent_Int

in

Identifier to determine maximal page size.

whereIdent_Str

in

Identifier of Text type. Condition to select from the table.

orderByIdent_Str

in

Identifier of Text type. Sorting in the final selection.

rowsCountIdent_Int

out

Identifier of Int type. The number of rows in the selection.

retCodeIdent_Int

out

Return code identifier.

transHandle_Int

in

Identifier for an unique number (handle) for the connection to the database.

mode_Int

in

Identifier of Int type - 0/1.

hintIdent_Str

in

Expression of String type that defines Oracle SQL hint. It is used as an instruction for the performance optimizer of SQL command. The value is used without the opening and terminating characters /*+ <orahint> */.
The example is mentioned here.

Note: In this situation, Oracle SQL hint is used for ESL action PG_READ, because in ESL action SQL_CONNECT SELECT expression is compounded for next called ESL action PG_READ.

 

Return code

The value of the parameter transHandle_Int. See the table of error codes. It is possible to get extended error information.

Description

Page access is initialized by the action PG_CONNECT. It performs the table opening, during which it is possible to specify conditions for the final selection (reduction of visible rows in the table). Selection is limited by the condition with the value whereIdent_Str. This text (a value of the identifier whereIdent_Str) is used in the clause WHERE in the SQL command.

The action allows to define a way to sort rows in the final selection by means of a value of the identifier orderByIdent_Str. The value of the identifier is used in the clause ORDER BY in the SQL command.

The required page size is defined by a value of the identifier pgSizeIdent_Int. This page size is to be used during reading from the table (whole page is read at the same time). A larger page may cause the big memory block allocation, and thereby to cause the malfunction of the operating system.
Maximum number of returned rows is limited by a Database configuration parameter Maximum returned rows.

After the successful opening a table (retCodeIdent_Int = _ERR_NO_ERROR), the identifier rowsCountIdent_Int contains the number of rows in the final selection and the identifier handleIdent_Int contains the number of the connection (handle).

If the parameter mode_Int = 1, the pages can be read only sequentially from 1 to maximal page. To move back is disabled. In this case, DbManager will use optimal way of reading from database. If parameter is not use, the value = 0.

Having finished a work with a table, it is necessary to close it using the action PG_DISCONNECT.

Related pages:

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