Comments on findJsonbValueFromSuperHeader()

diff --git a/src/backend/utils/adt/jsonb_support.c b/src/backend/utils/adt/jsonb_support.c
index 3580394a6c046bfd377f18dd6d5e091651d36aa6..2fba23fd2ebacf0db18dc3efb00ee857ca3fbd20 100644 (file)
--- a/src/backend/utils/adt/jsonb_support.c
+++ b/src/backend/utils/adt/jsonb_support.c
@@ -302,16 +302,22 @@ findJsonbValueFromSuperHeaderLen(JsonbSuperHeader sheader, uint32 flags,
 /*
  * Find string key in object or element by value in array.
  *
- * Returns palloc()'d copy of value.
+ * In order to proceed with the search, it is necessary for callers to have
+ * both specified an interest in a particular container type with an
+ * appropriate flag, as well as having the pointed-to Jsonb superheader be of
+ * that same container type at the top level.  If both of those conditions
+ * don't hold, immediately fall through and return NULL.  Otherwise, return
+ * palloc()'d copy of value.
  */
 JsonbValue *
 findJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
                              uint32 *lowbound, JsonbValue * key)
 {
-   uint32      superheader = *(uint32 *) sheader;
-   JEntry     *array = (JEntry *) (sheader + sizeof(uint32));
-   JsonbValue *r = palloc(sizeof(JsonbValue));
+   uint32          superheader = *(uint32 *) sheader;
+   JEntry         *array = (JEntry *) (sheader + sizeof(uint32));
+   JsonbValue     *r = palloc(sizeof(JsonbValue));
 
+   /* No contradictory requests */
    Assert((superheader & (JB_FARRAY | JB_FOBJECT)) !=
           (JB_FARRAY | JB_FOBJECT));
 
@@ -394,27 +400,28 @@ findJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
        Assert(key->type == jbvString);
 
        /*
-        * Binary search for matching jsonb value
+        * Binary search for matching jsonb value using "inner comparator"
+        * logic (i.e. not doing lexical comparisons).
         */
        while (stopLow < stopHigh)
        {
-           JEntry *e;
-           int     difference;
+           JEntry     *entry;
+           int         difference;
 
            stopMiddle = stopLow + (stopHigh - stopLow) / 2;
 
-           e = array + stopMiddle * 2;
+           entry = array + stopMiddle * 2;
 
            /* Equivalent to lengthCompareJsonbStringValue() */
-           if (key->string.len == JBE_LEN(*e))
-               difference = memcmp(data + JBE_OFF(*e), key->string.val,
+           if (key->string.len == JBE_LEN(*entry))
+               difference = memcmp(data + JBE_OFF(*entry), key->string.val,
                                    key->string.len);
            else
-               difference = (JBE_LEN(*e) > key->string.len) ? 1 : -1;
+               difference = (JBE_LEN(*entry) > key->string.len) ? 1 : -1;
 
            if (difference == 0)
            {
-               JEntry     *v = e + 1;
+               JEntry     *v = entry + 1;
 
                if (lowbound)
                    *lowbound = stopMiddle + 1;
@@ -429,7 +436,7 @@ findJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
                else if (JBE_ISBOOL(*v))
                {
                    r->type = jbvBool;
-                   r->boolean = (JBE_ISBOOL_TRUE(*v)) != 0;
+                   r->boolean = JBE_ISBOOL_TRUE(*v) != 0;
                    r->size = sizeof(JEntry);
                }
                else if (JBE_ISNUMERIC(*v))
@@ -455,13 +462,12 @@ findJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
 
                return r;
            }
-           else if (difference < 0)
-           {
-               stopLow = stopMiddle + 1;
-           }
            else
            {
-               stopHigh = stopMiddle;
+               if (difference < 0)
+                   stopLow = stopMiddle + 1;
+               else
+                   stopHigh = stopMiddle;
            }
        }
 
@@ -475,11 +481,11 @@ findJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
 /*
  * Get i-th value of array or object.
  *
- * Returns palloc()'d copy of value.
+ * Returns palloc()'d copy of value, or NULL if it cannot be found.
  */
 JsonbValue *
 getIthJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
-                               int32 i)
+                               uint32 i)
 {
    uint32      superheader = *(uint32 *) sheader;
    JsonbValue *r;
@@ -492,8 +498,6 @@ getIthJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
    Assert((superheader & (JB_FARRAY | JB_FOBJECT)) !=
           (JB_FARRAY | JB_FOBJECT));
 
-   Assert(i >= 0);
-
    if (i >= (superheader & JB_CMASK))
        return NULL;
 
@@ -524,7 +528,7 @@ getIthJsonbValueFromSuperHeader(JsonbSuperHeader sheader, uint32 flags,
    else if (JBE_ISBOOL(*e))
    {
        r->type = jbvBool;
-       r->boolean = (JBE_ISBOOL_TRUE(*e)) != 0;
+       r->boolean = JBE_ISBOOL_TRUE(*e) != 0;
        r->size = sizeof(JEntry);
    }
    else if (JBE_ISNUMERIC(*e))
@@ -745,7 +749,7 @@ JsonbIteratorNext(JsonbIterator ** it, JsonbValue * v, bool skipNested)
        }
    }
 
-   elog(ERROR, "unknown iterator res");
+   elog(ERROR, "invalid iterator state");
 }
 
 /*
@@ -828,8 +832,8 @@ lexicalCompareJsonbStringValue(const void *a, const void *b)
 static Size
 convertJsonb(JsonbValue * v, Jsonb *buffer)
 {
-   uint32      l = 0;
-   ConvertState state;
+   ConvertState    state;
+   Size            len = 0;
 
    /* Should not already have binary representation */
    Assert(v->type != jbvBinary);
@@ -842,10 +846,10 @@ convertJsonb(JsonbValue * v, Jsonb *buffer)
 
    walkJsonbValueConversion(v, &state, 0);
 
-   l = state.ptr - VARDATA(state.buffer);
+   len = state.ptr - VARDATA(state.buffer);
 
-   Assert(l <= v->size);
-   return l;
+   Assert(len <= v->size);
+   return len;
 }
 
 /*

diff --git a/src/include/utils/jsonb.h b/src/include/utils/jsonb.h
index cf042fbd109b0cb68a2183cc192b29d981b55a02..582cd30b57bf26bb084556927da6347e858d2016 100644 (file)
--- a/src/include/utils/jsonb.h
+++ b/src/include/utils/jsonb.h
@@ -288,7 +288,7 @@ extern JsonbValue *findJsonbValueFromSuperHeader(JsonbSuperHeader sheader,
                                                 uint32 *lowbound,
                                                 JsonbValue *key);
 extern JsonbValue *getIthJsonbValueFromSuperHeader(JsonbSuperHeader sheader,
-                                                  uint32 flags, int32 i);
+                                                  uint32 flags, uint32 i);
 extern JsonbValue *pushJsonbValue(ToJsonbState ** state, int r, JsonbValue *v);
 extern JsonbIterator *JsonbIteratorInit(JsonbSuperHeader buffer);
 extern int JsonbIteratorNext(JsonbIterator **it, JsonbValue *v, bool skipNested);