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pg_execute

Name

pg_execute -- send a query and optionally loop over the results

Synopsis

pg_execute ?-array arrayVar? ?-oid oidVar? conn commandString ?procedure?

Description

pg_execute submits a command to the PostgreSQL server.

If the command is not a SELECT statement, the number of rows affected by the command is returned. If the command is an INSERT statement and a single row is inserted, the OID of the inserted row is stored in the variable oidVar if the optional -oid argument is supplied.

If the command is a SELECT statement, then, for each row in the result, the row values are stored in the arrayVar variable, if supplied, using the column names as the array indices, else in variables named by the column names, and then the optional procedure is executed if supplied. (Omitting the procedure probably makes sense only if the query will return a single row.) The number of rows selected is returned.

The procedure can use the Tcl commands break, continue, and return with the expected behavior. Note that if the procedure executes return, then pg_execute does not return the number of affected rows.

pg_execute is a newer function which provides a superset of the features of pg_select and can replace pg_exec in many cases where access to the result handle is not needed.

For server-handled errors, pg_execute will throw a Tcl error and return a two-element list. The first element is an error code, such as PGRES_FATAL_ERROR, and the second element is the server error text. For more serious errors, such as failure to communicate with the server, pg_execute will throw a Tcl error and return just the error message text.

Arguments

-array arrayVar

Specifies the name of an array variable where result rows are stored, indexed by the column names. This is ignored if commandString is not a SELECT statement.

-oid oidVar

Specifies the name of a variable into which the OID from an INSERT statement will be stored.

conn

The handle of the connection on which to execute the command.

commandString

The SQL command to execute.

procedure

Optional procedure to execute for each result row of a SELECT statement.

Return Value

The number of rows affected or returned by the command.

Examples

In the following examples, error checking with catch has been omitted for clarity.

Insert a row and save the OID in result_oid:

pg_execute -oid result_oid $pgconn "INSERT INTO mytable VALUES (1);"

Print the columns item and value from each row:

pg_execute -array d $pgconn "SELECT item, value FROM mytable;" {
    puts "Item=$d(item) Value=$d(value)"
}

Find the maximum and minimum values and store them in $s(max) and $s(min):

pg_execute -array s $pgconn "SELECT max(value) AS max, min(value) AS min FROM mytable;"

Find the maximum and minimum values and store them in $max and $min:

pg_execute $pgconn "SELECT max(value) AS max, min(value) AS min FROM mytable;"
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