diff options
Diffstat (limited to 'src/include/tcop/dest.h')
| -rw-r--r-- | src/include/tcop/dest.h | 36 |
1 files changed, 20 insertions, 16 deletions
diff --git a/src/include/tcop/dest.h b/src/include/tcop/dest.h index d5ac420ce6e..c96133759d5 100644 --- a/src/include/tcop/dest.h +++ b/src/include/tcop/dest.h @@ -1,11 +1,13 @@ /*------------------------------------------------------------------------- * * dest.h - * Whenever the backend executes a query, the results - * have to go someplace. + * support for communication destinations + * + * Whenever the backend executes a query, the results + * have to go someplace. * * - stdout is the destination only when we are running a - * backend without a postmaster and are returning results + * standalone backend (no postmaster) and are returning results * back to an interactive user. * * - a remote process is the destination when we are @@ -14,15 +16,21 @@ * to the frontend via the functions in backend/libpq. * * - None is the destination when the system executes - * a query internally. This is not used now but it may be - * useful for the parallel optimiser/executor. + * a query internally. The results are discarded. * * dest.c defines three functions that implement destination management: * - * BeginCommand: initialize the destination. + * BeginCommand: initialize the destination at start of command. * DestToFunction: return a pointer to a struct of destination-specific * receiver functions. - * EndCommand: clean up the destination when output is complete. + * EndCommand: clean up the destination at end of command. + * + * BeginCommand/EndCommand are executed once per received SQL query. + * + * DestToFunction, and the receiver functions it links to, are executed + * each time we run the executor to produce tuples, which may occur + * multiple times per received query (eg, due to additional queries produced + * by rewrite rules). * * The DestReceiver object returned by DestToFunction may be a statically * allocated object (for destination types that require no local state) @@ -32,14 +40,11 @@ * by casting the DestReceiver* pointer passed to them. * The palloc'd object is pfree'd by the DestReceiver's cleanup function. * - * XXX FIXME: the initialization and cleanup code that currently appears - * in-line in BeginCommand and EndCommand probably should be moved out - * to routines associated with each destination receiver type. * * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: dest.h,v 1.29 2002/02/26 22:47:11 tgl Exp $ + * $Id: dest.h,v 1.30 2002/02/27 19:36:13 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -80,18 +85,17 @@ struct _DestReceiver { /* Called for each tuple to be output: */ void (*receiveTuple) (HeapTuple tuple, TupleDesc typeinfo, - DestReceiver *self); + DestReceiver *self); /* Initialization and teardown: */ - void (*setup) (DestReceiver *self, TupleDesc typeinfo); + void (*setup) (DestReceiver *self, int operation, + const char *portalName, TupleDesc typeinfo); void (*cleanup) (DestReceiver *self); /* Private fields might appear beyond this point... */ }; /* The primary destination management functions */ -extern void BeginCommand(char *pname, int operation, TupleDesc attinfo, - bool isIntoRel, bool isIntoPortal, char *tag, - CommandDest dest); +extern void BeginCommand(const char *commandTag, CommandDest dest); extern DestReceiver *DestToFunction(CommandDest dest); extern void EndCommand(const char *commandTag, CommandDest dest); |