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Restructure index access method API to hide most of it at the C level.

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This patch reduces pg_am to just two columns, a name and a handler
function.  All the data formerly obtained from pg_am is now provided
in a C struct returned by the handler function.  This is similar to
the designs we've adopted for FDWs and tablesample methods.  There
are multiple advantages.  For one, the index AM's support functions
are now simple C functions, making them faster to call and much less
error-prone, since the C compiler can now check function signatures.
For another, this will make it far more practical to define index access
methods in installable extensions.

A disadvantage is that SQL-level code can no longer see attributes
of index AMs; in particular, some of the crosschecks in the opr_sanity
regression test are no longer possible from SQL.  We've addressed that
by adding a facility for the index AM to perform such checks instead.
(Much more could be done in that line, but for now we're content if the
amvalidate functions more or less replace what opr_sanity used to do.)
We might also want to expose some sort of reporting functionality, but
this patch doesn't do that.

Alexander Korotkov, reviewed by Petr Jelínek, and rather heavily
editorialized on by me.
This commit is contained in:
Tom Lane
2016-01-17 19:36:59 -05:00
parent 8d290c8ec6
commit 65c5fcd353
93 changed files with 2493 additions and 1924 deletions
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41
src/backend/access/gist/gistscan.c
View File

@ -54,12 +54,9 @@ pairingheap_GISTSearchItem_cmp(const pairingheap_node *a, const pairingheap_node
* Index AM API functions for scanning GiST indexes
*/
Datum
gistbeginscan(PG_FUNCTION_ARGS)
IndexScanDesc
gistbeginscan(Relation r, int nkeys, int norderbys)
{
Relation r = (Relation) PG_GETARG_POINTER(0);
int nkeys = PG_GETARG_INT32(1);
int norderbys = PG_GETARG_INT32(2);
IndexScanDesc scan;
GISTSTATE *giststate;
GISTScanOpaque so;
@ -107,16 +104,13 @@ gistbeginscan(PG_FUNCTION_ARGS)
MemoryContextSwitchTo(oldCxt);
PG_RETURN_POINTER(scan);
return scan;
}
Datum
gistrescan(PG_FUNCTION_ARGS)
void
gistrescan(IndexScanDesc scan, ScanKey key, int nkeys,
ScanKey orderbys, int norderbys)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
ScanKey key = (ScanKey) PG_GETARG_POINTER(1);
ScanKey orderbys = (ScanKey) PG_GETARG_POINTER(3);
/* nkeys and norderbys arguments are ignored */
GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
bool first_time;
@ -314,28 +308,11 @@ gistrescan(PG_FUNCTION_ARGS)
if (!first_time)
pfree(fn_extras);
}
PG_RETURN_VOID();
}
Datum
gistmarkpos(PG_FUNCTION_ARGS)
void
gistendscan(IndexScanDesc scan)
{
elog(ERROR, "GiST does not support mark/restore");
PG_RETURN_VOID();
}
Datum
gistrestrpos(PG_FUNCTION_ARGS)
{
elog(ERROR, "GiST does not support mark/restore");
PG_RETURN_VOID();
}
Datum
gistendscan(PG_FUNCTION_ARGS)
{
IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
/*
@ -343,6 +320,4 @@ gistendscan(PG_FUNCTION_ARGS)
* as well as the queueCxt if there is a separate context for it.
*/
freeGISTstate(so->giststate);
PG_RETURN_VOID();
}