postgresql/contrib/hstore/hstore_subs.c

298 lines
7.8 KiB
C

/*-------------------------------------------------------------------------
*
* hstore_subs.c
* Subscripting support functions for hstore.
*
* This is a great deal simpler than array_subs.c, because the result of
* subscripting an hstore is just a text string (the value for the key).
* We do not need to support array slicing notation, nor multiple subscripts.
* Less obviously, because the subscript result is never a SQL container
* type, there will never be any nested-assignment scenarios, so we do not
* need a fetch_old function. In turn, that means we can drop the
* check_subscripts function and just let the fetch and assign functions
* do everything.
*
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* contrib/hstore/hstore_subs.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "executor/execExpr.h"
#include "hstore.h"
#include "nodes/nodeFuncs.h"
#include "nodes/subscripting.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "utils/builtins.h"
/*
* Finish parse analysis of a SubscriptingRef expression for hstore.
*
* Verify there's just one subscript, coerce it to text,
* and set the result type of the SubscriptingRef node.
*/
static void
hstore_subscript_transform(SubscriptingRef *sbsref,
List *indirection,
ParseState *pstate,
bool isSlice,
bool isAssignment)
{
A_Indices *ai;
Node *subexpr;
/* We support only single-subscript, non-slice cases */
if (isSlice || list_length(indirection) != 1)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("hstore allows only one subscript"),
parser_errposition(pstate,
exprLocation((Node *) indirection))));
/* Transform the subscript expression to type text */
ai = linitial_node(A_Indices, indirection);
Assert(ai->uidx != NULL && ai->lidx == NULL && !ai->is_slice);
subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
/* If it's not text already, try to coerce */
subexpr = coerce_to_target_type(pstate,
subexpr, exprType(subexpr),
TEXTOID, -1,
COERCION_ASSIGNMENT,
COERCE_IMPLICIT_CAST,
-1);
if (subexpr == NULL)
ereport(ERROR,
(errcode(ERRCODE_DATATYPE_MISMATCH),
errmsg("hstore subscript must have type text"),
parser_errposition(pstate, exprLocation(ai->uidx))));
/* ... and store the transformed subscript into the SubscriptRef node */
sbsref->refupperindexpr = list_make1(subexpr);
sbsref->reflowerindexpr = NIL;
/* Determine the result type of the subscripting operation; always text */
sbsref->refrestype = TEXTOID;
sbsref->reftypmod = -1;
}
/*
* Evaluate SubscriptingRef fetch for hstore.
*
* Source container is in step's result variable (it's known not NULL, since
* we set fetch_strict to true), and the subscript expression is in the
* upperindex[] array.
*/
static void
hstore_subscript_fetch(ExprState *state,
ExprEvalStep *op,
ExprContext *econtext)
{
SubscriptingRefState *sbsrefstate = op->d.sbsref.state;
HStore *hs;
text *key;
HEntry *entries;
int idx;
text *out;
/* Should not get here if source hstore is null */
Assert(!(*op->resnull));
/* Check for null subscript */
if (sbsrefstate->upperindexnull[0])
{
*op->resnull = true;
return;
}
/* OK, fetch/detoast the hstore and subscript */
hs = DatumGetHStoreP(*op->resvalue);
key = DatumGetTextPP(sbsrefstate->upperindex[0]);
/* The rest is basically the same as hstore_fetchval() */
entries = ARRPTR(hs);
idx = hstoreFindKey(hs, NULL,
VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));
if (idx < 0 || HSTORE_VALISNULL(entries, idx))
{
*op->resnull = true;
return;
}
out = cstring_to_text_with_len(HSTORE_VAL(entries, STRPTR(hs), idx),
HSTORE_VALLEN(entries, idx));
*op->resvalue = PointerGetDatum(out);
}
/*
* Evaluate SubscriptingRef assignment for hstore.
*
* Input container (possibly null) is in result area, replacement value is in
* SubscriptingRefState's replacevalue/replacenull.
*/
static void
hstore_subscript_assign(ExprState *state,
ExprEvalStep *op,
ExprContext *econtext)
{
SubscriptingRefState *sbsrefstate = op->d.sbsref.state;
text *key;
Pairs p;
HStore *out;
/* Check for null subscript */
if (sbsrefstate->upperindexnull[0])
ereport(ERROR,
(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
errmsg("hstore subscript in assignment must not be null")));
/* OK, fetch/detoast the subscript */
key = DatumGetTextPP(sbsrefstate->upperindex[0]);
/* Create a Pairs entry for subscript + replacement value */
p.needfree = false;
p.key = VARDATA_ANY(key);
p.keylen = hstoreCheckKeyLen(VARSIZE_ANY_EXHDR(key));
if (sbsrefstate->replacenull)
{
p.vallen = 0;
p.isnull = true;
}
else
{
text *val = DatumGetTextPP(sbsrefstate->replacevalue);
p.val = VARDATA_ANY(val);
p.vallen = hstoreCheckValLen(VARSIZE_ANY_EXHDR(val));
p.isnull = false;
}
if (*op->resnull)
{
/* Just build a one-element hstore (cf. hstore_from_text) */
out = hstorePairs(&p, 1, p.keylen + p.vallen);
}
else
{
/*
* Otherwise, merge the new key into the hstore. Based on
* hstore_concat.
*/
HStore *hs = DatumGetHStoreP(*op->resvalue);
int s1count = HS_COUNT(hs);
int outcount = 0;
int vsize;
char *ps1,
*bufd,
*pd;
HEntry *es1,
*ed;
int s1idx;
int s2idx;
/* Allocate result without considering possibility of duplicate */
vsize = CALCDATASIZE(s1count + 1, VARSIZE(hs) + p.keylen + p.vallen);
out = palloc(vsize);
SET_VARSIZE(out, vsize);
HS_SETCOUNT(out, s1count + 1);
ps1 = STRPTR(hs);
bufd = pd = STRPTR(out);
es1 = ARRPTR(hs);
ed = ARRPTR(out);
for (s1idx = s2idx = 0; s1idx < s1count || s2idx < 1; ++outcount)
{
int difference;
if (s1idx >= s1count)
difference = 1;
else if (s2idx >= 1)
difference = -1;
else
{
int s1keylen = HSTORE_KEYLEN(es1, s1idx);
int s2keylen = p.keylen;
if (s1keylen == s2keylen)
difference = memcmp(HSTORE_KEY(es1, ps1, s1idx),
p.key,
s1keylen);
else
difference = (s1keylen > s2keylen) ? 1 : -1;
}
if (difference >= 0)
{
HS_ADDITEM(ed, bufd, pd, p);
++s2idx;
if (difference == 0)
++s1idx;
}
else
{
HS_COPYITEM(ed, bufd, pd,
HSTORE_KEY(es1, ps1, s1idx),
HSTORE_KEYLEN(es1, s1idx),
HSTORE_VALLEN(es1, s1idx),
HSTORE_VALISNULL(es1, s1idx));
++s1idx;
}
}
HS_FINALIZE(out, outcount, bufd, pd);
}
*op->resvalue = PointerGetDatum(out);
*op->resnull = false;
}
/*
* Set up execution state for an hstore subscript operation.
*/
static void
hstore_exec_setup(const SubscriptingRef *sbsref,
SubscriptingRefState *sbsrefstate,
SubscriptExecSteps *methods)
{
/* Assert we are dealing with one subscript */
Assert(sbsrefstate->numlower == 0);
Assert(sbsrefstate->numupper == 1);
/* We can't check upperprovided[0] here, but it must be true */
/* Pass back pointers to appropriate step execution functions */
methods->sbs_check_subscripts = NULL;
methods->sbs_fetch = hstore_subscript_fetch;
methods->sbs_assign = hstore_subscript_assign;
methods->sbs_fetch_old = NULL;
}
/*
* hstore_subscript_handler
* Subscripting handler for hstore.
*/
PG_FUNCTION_INFO_V1(hstore_subscript_handler);
Datum
hstore_subscript_handler(PG_FUNCTION_ARGS)
{
static const SubscriptRoutines sbsroutines = {
.transform = hstore_subscript_transform,
.exec_setup = hstore_exec_setup,
.fetch_strict = true, /* fetch returns NULL for NULL inputs */
.fetch_leakproof = true, /* fetch returns NULL for bad subscript */
.store_leakproof = false /* ... but assignment throws error */
};
PG_RETURN_POINTER(&sbsroutines);
}