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postgresql/src/include/executor/tstoreReceiver.h

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2003-03-27 17:55:11 +01:00
/*-------------------------------------------------------------------------
*
* tstoreReceiver.h
* prototypes for tstoreReceiver.c
*
*
Update copyright for 2022 Backpatch-through: 10
2022-01-08 01:04:57 +01:00
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
*
Remove cvs keywords from all files.
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* src/include/executor/tstoreReceiver.h
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*
*-------------------------------------------------------------------------
*/
#ifndef TSTORE_RECEIVER_H
#define TSTORE_RECEIVER_H
#include "tcop/dest.h"
Restructure command destination handling so that we pass around DestReceiver pointers instead of just CommandDest values. The DestReceiver is made at the point where the destination is selected, rather than deep inside the executor. This cleans up the original kluge implementation of tstoreReceiver.c, and makes it easy to support retrieving results from utility statements inside portals. Thus, you can now do fun things like Bind and Execute a FETCH or EXPLAIN command, and it'll all work as expected (e.g., you can Describe the portal, or use Execute's count parameter to suspend the output partway through). Implementation involves stuffing the utility command's output into a Tuplestore, which would be kind of annoying for huge output sets, but should be quite acceptable for typical uses of utility commands.
2003-05-06 22:26:28 +02:00
#include "utils/tuplestore.h"
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2003-03-27 17:55:11 +01:00
Restructure command destination handling so that we pass around DestReceiver pointers instead of just CommandDest values. The DestReceiver is made at the point where the destination is selected, rather than deep inside the executor. This cleans up the original kluge implementation of tstoreReceiver.c, and makes it easy to support retrieving results from utility statements inside portals. Thus, you can now do fun things like Bind and Execute a FETCH or EXPLAIN command, and it'll all work as expected (e.g., you can Describe the portal, or use Execute's count parameter to suspend the output partway through). Implementation involves stuffing the utility command's output into a Tuplestore, which would be kind of annoying for huge output sets, but should be quite acceptable for typical uses of utility commands.
2003-05-06 22:26:28 +02:00
Clean up the API for DestReceiver objects by eliminating the assumption that a Portal is a useful and sufficient additional argument for CreateDestReceiver --- it just isn't, in most cases. Instead formalize the approach of passing any needed parameters to the receiver separately. One unexpected benefit of this change is that we can declare typedef Portal in a less surprising location. This patch is just code rearrangement and doesn't change any functionality. I'll tackle the HOLD-cursor-vs-toast problem in a follow-on patch.
2008-11-30 21:51:25 +01:00
extern DestReceiver *CreateTuplestoreDestReceiver(void);
extern void SetTuplestoreDestReceiverParams(DestReceiver *self,
Tuplestorestate *tStore,
Ensure that the contents of a holdable cursor don't depend on out-of-line toasted values, since those could get dropped once the cursor's transaction is over. Per bug #4553 from Andrew Gierth. Back-patch as far as 8.1. The bug actually exists back to 7.4 when holdable cursors were introduced, but this patch won't work before 8.1 without significant adjustments. Given the lack of field complaints, it doesn't seem worth the work (and risk of introducing new bugs) to try to make a patch for the older branches.
2008-12-01 18:06:21 +01:00
MemoryContext tContext,
Avoid using a cursor in plpgsql's RETURN QUERY statement. plpgsql has always executed the query given in a RETURN QUERY command by opening it as a cursor and then fetching a few rows at a time, which it turns around and dumps into the function's result tuplestore. The point of this was to keep from blowing out memory with an oversized SPITupleTable result (note that while a tuplestore can spill tuples to disk, SPITupleTable cannot). However, it's rather inefficient, both because of extra data copying and because of executor entry/exit overhead. In recent versions, a new performance problem has emerged: use of a cursor prevents use of a parallel plan for the executed query. We can improve matters by skipping use of a cursor and having the executor push result tuples directly into the function's result tuplestore. However, a moderate amount of new infrastructure is needed to make that idea work: * We can use the existing tstoreReceiver.c DestReceiver code to funnel executor output to the tuplestore, but it has to be extended to support plpgsql's requirement for possibly applying a tuple conversion map. * SPI needs to be extended to allow use of a caller-supplied DestReceiver instead of its usual receiver that puts tuples into a SPITupleTable. Two new API calls are needed to handle both the RETURN QUERY and RETURN QUERY EXECUTE cases. I also felt that I didn't want these new API calls to use the legacy method of specifying query parameter values with "char" null flags (the old ' '/'n' convention); rather they should accept ParamListInfo objects containing the parameter type and value info. This required a bit of additional new infrastructure since we didn't yet have any parse analysis callback that would interpret $N parameter symbols according to type data supplied in a ParamListInfo. There seems to be no harm in letting makeParamList install that callback by default, rather than leaving a new ParamListInfo's parserSetup hook as NULL. (Indeed, as of HEAD, I couldn't find anyplace that was using the parserSetup field at all; plpgsql was using parserSetupArg for its own purposes, but parserSetup seemed to be write-only.) We can actually get plpgsql out of the business of using legacy null flags altogether, and using ParamListInfo instead of its ad-hoc PreparedParamsData structure; but this requires inventing one more SPI API call that can replace SPI_cursor_open_with_args. That seems worth doing, though. SPI_execute_with_args and SPI_cursor_open_with_args are now unused anywhere in the core PG distribution. Perhaps someday we could deprecate/remove them. But cleaning up the crufty bits of the SPI API is a task for a different patch. Per bug #16040 from Jeremy Smith. This is unfortunately too invasive to consider back-patching. Patch by me; thanks to Hamid Akhtar for review. Discussion: https://postgr.es/m/16040-eaacad11fecfb198@postgresql.org
2020-06-12 18:14:32 +02:00
bool detoast,
TupleDesc target_tupdesc,
const char *map_failure_msg);
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2003-03-27 17:55:11 +01:00
#endif /* TSTORE_RECEIVER_H */