--- /dev/null
+/*-------------------------------------------------------------------------
+ *
+ * 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) 1996-2020, 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);
+}
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