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Executes an SQL command given as a string. An error in the command causes an error to be raised. Otherwise, the return value ofspi_exec is the number of rows processed (selected, inserted, updated, or deleted) by the command, or zero if the command is a utility statement. In addition, if the command is aSELECT statement, the values of the selected columns are placed in Tcl variables as described below.

The optional-count value tellsspi_exec to stop oncen rows have been retrieved, much as if the query included aLIMIT clause. Ifn is zero, the query is run to completion, the same as when-count is omitted.

If the command is aSELECT statement, the values of the result columns are placed into Tcl variables named after the columns. If the-array option is given, the column values are instead stored into elements of the named associative array, with the column names used as array indexes. In addition, the current row number within the result (counting from zero) is stored into the array element named“.tupno”, unless that name is in use as a column name in the result.

If the command is aSELECT statement and noloop-body script is given, then only the first row of results are stored into Tcl variables or array elements; remaining rows, if any, are ignored. No storing occurs if the query returns no rows. (This case can be detected by checking the result ofspi_exec.) For example:

spi_exec "SELECT count(*) AS cnt FROM pg_proc"

will set the Tcl variable$cnt to the number of rows in thepg_proc system catalog.

If the optionalloop-body argument is given, it is a piece of Tcl script that is executed once for each row in the query result. (loop-body is ignored if the given command is not aSELECT.) The values of the current row's columns are stored into Tcl variables or array elements before each iteration. For example:

spi_exec -array C "SELECT * FROM pg_class" {    elog DEBUG "have table $C(relname)"}

will print a log message for every row ofpg_class. This feature works similarly to other Tcl looping constructs; in particularcontinue andbreak work in the usual way inside the loop body.

If a column of a query result is null, the target variable for it is“unset” rather than being set.

Prepares and saves a query plan for later execution. The saved plan will be retained for the life of the current session.

The query can use parameters, that is, placeholders for values to be supplied whenever the plan is actually executed. In the query string, refer to parameters by the symbols$1 ...$n. If the query uses parameters, the names of the parameter types must be given as a Tcl list. (Write an empty list fortypelist if no parameters are used.)

The return value fromspi_prepare is a query ID to be used in subsequent calls tospi_execp. Seespi_execp for an example.

Executes a query previously prepared withspi_prepare.queryid is the ID returned byspi_prepare. If the query references parameters, avalue-list must be supplied. This is a Tcl list of actual values for the parameters. The list must be the same length as the parameter type list previously given tospi_prepare. Omitvalue-list if the query has no parameters.

The optional value for-nulls is a string of spaces and'n' characters tellingspi_execp which of the parameters are null values. If given, it must have exactly the same length as thevalue-list. If it is not given, all the parameter values are nonnull.

Except for the way in which the query and its parameters are specified,spi_execp works just likespi_exec. The-count,-array, andloop-body options are the same, and so is the result value.

Here's an example of a PL/Tcl function using a prepared plan:

CREATE FUNCTION t1_count(integer, integer) RETURNS integer AS $$    if {![ info exists GD(plan) ]} {        # prepare the saved plan on the first call        set GD(plan) [ spi_prepare \                "SELECT count(*) AS cnt FROM t1 WHERE num >= \$1 AND num <= \$2" \                [ list int4 int4 ] ]    }    spi_execp -count 1 $GD(plan) [ list $1 $2 ]    return $cnt$$ LANGUAGE pltcl;

We need backslashes inside the query string given tospi_prepare to ensure that the$n markers will be passed through tospi_prepare as-is, and not replaced by Tcl variable substitution.

Returns the OID of the row inserted by the lastspi_exec orspi_execp, if the command was a single-rowINSERT and the modified table contained OIDs. (If not, you get zero.)

The Tcl script contained incommand is executed within a SQL subtransaction. If the script returns an error, that entire subtransaction is rolled back before returning the error out to the surrounding Tcl code. SeeSection 45.9 for more details and an example.

Doubles all occurrences of single quote and backslash characters in the given string. This can be used to safely quote strings that are to be inserted into SQL commands given tospi_exec orspi_prepare. For example, think about an SQL command string like:

"SELECT '$val' AS ret"

where the Tcl variableval actually containsdoesn't. This would result in the final command string:

SELECT 'doesn't' AS ret

which would cause a parse error duringspi_exec orspi_prepare. To work properly, the submitted command should contain:

SELECT 'doesn''t' AS ret

which can be formed in PL/Tcl using:

"SELECT '[ quote $val ]' AS ret"

One advantage ofspi_execp is that you don't have to quote parameter values like this, since the parameters are never parsed as part of an SQL command string.

Emits a log or error message. Possible levels areDEBUG,LOG,INFO,NOTICE,WARNING,ERROR, andFATAL.ERROR raises an error condition; if this is not trapped by the surrounding Tcl code, the error propagates out to the calling query, causing the current transaction or subtransaction to be aborted. This is effectively the same as the Tclerror command.FATAL aborts the transaction and causes the current session to shut down. (There is probably no good reason to use this error level in PL/Tcl functions, but it's provided for completeness.) The other levels only generate messages of different priority levels. Whether messages of a particular priority are reported to the client, written to the server log, or both is controlled by thelog_min_messages andclient_min_messages configuration variables. SeeChapter 19 andSection 45.8 for more information.